Design Optimization of PZT-Based Piezoelectric Cantilever Beam by Using Computational Experiments
Kim, Jihoon; Park, Sanghyun; Lim, Woochul; Jang, Junyong; Lee, Tae Hee; Hong, Seong Kwang; Song, Yewon; Sung, Tae Hyun
2016-08-01
Piezoelectric energy harvesting is gaining huge research interest since it provides high power density and has real-life applicability. However, investigative research for the mechanical-electrical coupling phenomenon remains challenging. Many researchers depend on physical experiments to choose devices with the best performance which meet design objectives through case analysis; this involves high design costs. This study aims to develop a practical model using computer simulations and to propose an optimized design for a lead zirconate titanate (PZT)-based piezoelectric cantilever beam which is widely used in energy harvesting. In this study, the commercial finite element (FE) software is used to predict the voltage generated from vibrations of the PZT-based piezoelectric cantilever beam. Because the initial FE model differs from physical experiments, the model is calibrated by multi-objective optimization to increase the accuracy of the predictions. We collect data from physical experiments using the cantilever beam and use these experimental results in the calibration process. Since dynamic analysis in the FE analysis of the piezoelectric cantilever beam with a dense step size is considerably time-consuming, a surrogate model is employed for efficient optimization. Through the design optimization of the PZT-based piezoelectric cantilever beam, a high-performance piezoelectric device was developed. The sensitivity of the variables at the optimum design is analyzed to suggest a further improved device.
Design Optimization of PZT-Based Piezoelectric Cantilever Beam by Using Computational Experiments
Kim, Jihoon; Park, Sanghyun; Lim, Woochul; Jang, Junyong; Lee, Tae Hee; Hong, Seong Kwang; Song, Yewon; Sung, Tae Hyun
2016-04-01
Piezoelectric energy harvesting is gaining huge research interest since it provides high power density and has real-life applicability. However, investigative research for the mechanical-electrical coupling phenomenon remains challenging. Many researchers depend on physical experiments to choose devices with the best performance which meet design objectives through case analysis; this involves high design costs. This study aims to develop a practical model using computer simulations and to propose an optimized design for a lead zirconate titanate (PZT)-based piezoelectric cantilever beam which is widely used in energy harvesting. In this study, the commercial finite element (FE) software is used to predict the voltage generated from vibrations of the PZT-based piezoelectric cantilever beam. Because the initial FE model differs from physical experiments, the model is calibrated by multi-objective optimization to increase the accuracy of the predictions. We collect data from physical experiments using the cantilever beam and use these experimental results in the calibration process. Since dynamic analysis in the FE analysis of the piezoelectric cantilever beam with a dense step size is considerably time-consuming, a surrogate model is employed for efficient optimization. Through the design optimization of the PZT-based piezoelectric cantilever beam, a high-performance piezoelectric device was developed. The sensitivity of the variables at the optimum design is analyzed to suggest a further improved device.
Monte Carlo vs. Pencil Beam based optimization of stereotactic lung IMRT
Weinmann Martin; Söhn Matthias; Muzik Jan; Sikora Marcin; Alber Markus
2009-01-01
Abstract Background The purpose of the present study is to compare finite size pencil beam (fsPB) and Monte Carlo (MC) based optimization of lung intensity-modulated stereotactic radiotherapy (lung IMSRT). Materials and methods A fsPB and a MC algorithm as implemented in a biological IMRT planning system were validated by film measurements in a static lung phantom. Then, they were applied for static lung IMSRT planning based on three different geometrical patient models (one phase static CT, ...
Monte Carlo vs. Pencil Beam based optimization of stereotactic lung IMRT
Sikora, Marcin; Muzik, Jan; Söhn, Matthias; Weinmann, Martin; Alber, Markus
2009-01-01
Background The purpose of the present study is to compare finite size pencil beam (fsPB) and Monte Carlo (MC) based optimization of lung intensity-modulated stereotactic radiotherapy (lung IMSRT). Materials and methods A fsPB and a MC algorithm as implemented in a biological IMRT planning system were validated by film measurements in a static lung phantom. Then, they were applied for static lung IMSRT planning based on three different geometrical patient models (one phase static CT, density o...
Monte Carlo vs. Pencil Beam based optimization of stereotactic lung IMRT
Sikora, Marcin Pawel; Muzik, Jan; Söhn, Matthias; Weinmann, Martin; Alber, Markus
2009-01-01
Background: The purpose of the present study is to compare finite size pencil beam (fsPB) and Monte Carlo (MC) based optimization of lung intensity-modulated stereotactic radiotherapy (lung IMSRT). Materials and methods: A fsPB and a MC algorithm as implemented in a biological IMRT planning system were validated by film measurements in a static lung phantom. Then, they were applied for static lung IMSRT planning based on three different geometrical patient models (one phase ...
Optimal beam focusing through turbulence.
Charnotskii, Mikhail
2015-11-01
Beam spread and beam wandering are the most perceptible effects of atmospheric turbulence on propagating laser beams. The width of the mean irradiance profile is typically used to characterize the beam spread. This so-called long-term (LT) statistic allows for a relatively simple theoretical description. However, the LT beam size is not a very practical measure of the beam spread because its measurements are sensitive to the movements of the source and detector, and to the large-scale variations of the refractive index that are not associated with turbulence. The short-term (ST) beam spread is measured relative to the instantaneous position of the beam center and is free of these drawbacks, but has not been studied as thoroughly as the LT spread. We present a theoretical model for the ST beam irradiance that is based on the parabolic equation for the beam wave propagation in random media, and the Markov approximation for calculation of the statistics of the optical field, and discuss an approximation that allows introduction of the isoplanatic ST point spread function (PSF). Unlike the LT PSF, the ST PSF depends on the overall beam geometry. This allows optimization of the initial beam field in terms of minimizing the ST beam size at the observation plane. Calculations supporting this conjecture are presented for the simple case of the coherent Gaussian beam, and Kolmogorov turbulence. PMID:26560908
Monte Carlo vs. Pencil Beam based optimization of stereotactic lung IMRT
International Nuclear Information System (INIS)
The purpose of the present study is to compare finite size pencil beam (fsPB) and Monte Carlo (MC) based optimization of lung intensity-modulated stereotactic radiotherapy (lung IMSRT). A fsPB and a MC algorithm as implemented in a biological IMRT planning system were validated by film measurements in a static lung phantom. Then, they were applied for static lung IMSRT planning based on three different geometrical patient models (one phase static CT, density overwrite one phase static CT, average CT) of the same patient. Both 6 and 15 MV beam energies were used. The resulting treatment plans were compared by how well they fulfilled the prescribed optimization constraints both for the dose distributions calculated on the static patient models and for the accumulated dose, recalculated with MC on each of 8 CTs of a 4DCT set. In the phantom measurements, the MC dose engine showed discrepancies < 2%, while the fsPB dose engine showed discrepancies of up to 8% in the presence of lateral electron disequilibrium in the target. In the patient plan optimization, this translates into violations of organ at risk constraints and unpredictable target doses for the fsPB optimized plans. For the 4D MC recalculated dose distribution, MC optimized plans always underestimate the target doses, but the organ at risk doses were comparable. The results depend on the static patient model, and the smallest discrepancy was found for the MC optimized plan on the density overwrite one phase static CT model. It is feasible to employ the MC dose engine for optimization of lung IMSRT and the plans are superior to fsPB. Use of static patient models introduces a bias in the MC dose distribution compared to the 4D MC recalculated dose, but this bias is predictable and therefore MC based optimization on static patient models is considered safe
An Optimal Sorting of Pulse Amplitude Sequence Based on the Phased Array Radar Beam Tasks
Institute of Scientific and Technical Information of China (English)
Chuan Sheng∗,Yongshun Zhang; Wenlong Lu
2016-01-01
The study of phased array radar ( PAR) pulse amplitude sequence characteristics is the key to understand the radar’s working state and its beam’s scanning manner. According to the principle of antenna pattern formation and the searching and tracking modes of beams, this paper analyzes the characteristics and differences of pulse amplitude sequence when the radar beams work in searching and tracking modes respectively. Then an optimal sorting model of pulse amplitude sequence is established based on least⁃squares and curve⁃fitting methods. This method is helpful for acquiring the current working state of the radar and recognizing its instantaneous beam pointing by sorting the pulse amplitude sequence without the necessity to estimate the antenna pattern.
Monte Carlo vs. Pencil Beam based optimization of stereotactic lung IMRT
Directory of Open Access Journals (Sweden)
Weinmann Martin
2009-12-01
Full Text Available Abstract Background The purpose of the present study is to compare finite size pencil beam (fsPB and Monte Carlo (MC based optimization of lung intensity-modulated stereotactic radiotherapy (lung IMSRT. Materials and methods A fsPB and a MC algorithm as implemented in a biological IMRT planning system were validated by film measurements in a static lung phantom. Then, they were applied for static lung IMSRT planning based on three different geometrical patient models (one phase static CT, density overwrite one phase static CT, average CT of the same patient. Both 6 and 15 MV beam energies were used. The resulting treatment plans were compared by how well they fulfilled the prescribed optimization constraints both for the dose distributions calculated on the static patient models and for the accumulated dose, recalculated with MC on each of 8 CTs of a 4DCT set. Results In the phantom measurements, the MC dose engine showed discrepancies Conclusions It is feasible to employ the MC dose engine for optimization of lung IMSRT and the plans are superior to fsPB. Use of static patient models introduces a bias in the MC dose distribution compared to the 4D MC recalculated dose, but this bias is predictable and therefore MC based optimization on static patient models is considered safe.
International Nuclear Information System (INIS)
Measuring the beam transverse emittance is fundamental in every accelerator, in particular for colliders, where its precise determination is essential to maximize the luminosity and thus the performance of the colliding beams. Synchrotron Radiation (SR) is a versatile tool for non-destructive beam diagnostics, since its characteristics are closely related to those of the source beam. At CERN, being the only available diagnostics at high beam intensity and energy, SR monitors are exploited as the proton beam size monitor of the two higher energy machines, the Super Proton Synchrotron (SPS) and the Large Hadron Collider (LHC). The thesis work documented in this report focused on the design, development, characterization and optimization of these beam size monitors. Such studies were based on a comprehensive set of theoretical calculations, numerical simulations and experiments. A powerful simulation tool has been developed combining conventional softwares for SR simulation and optics design, thus allowing the description of an SR monitor from its source up to the detector. The simulations were confirmed by direct observations, and a detailed performance studies of the operational SR imaging monitor in the LHC, where different techniques for experimentally validating the system were applied, such as cross-calibrations with the wire scanners at low intensity (that are considered as a reference) and direct comparison with beam sizes de-convoluted from the LHC luminosity measurements. In 2015, the beam sizes to be measured with the further increase of the LHC beam energy to 7 TeV will decrease down to ∼190 μm. In these conditions, the SR imaging technique was found at its limits of applicability since the error on the beam size determination is proportional to the ratio of the system resolution and the measured beam size. Therefore, various solutions were probed to improve the system's performance such as the choice of one light polarization, the reduction of
Yamaguchi, Hideshi; Soeda, Takeshi
2015-03-01
A practical framework for an electron beam induced current (EBIC) technique has been established for conductive materials based on a numerical optimization approach. Although the conventional EBIC technique is useful for evaluating the distributions of dopants or crystal defects in semiconductor transistors, issues related to the reproducibility and quantitative capability of measurements using this technique persist. For instance, it is difficult to acquire high-quality EBIC images throughout continuous tests due to variation in operator skill or test environment. Recently, due to the evaluation of EBIC equipment performance and the numerical optimization of equipment items, the constant acquisition of high contrast images has become possible, improving the reproducibility as well as yield regardless of operator skill or test environment. The technique proposed herein is even more sensitive and quantitative than scanning probe microscopy, an imaging technique that can possibly damage the sample. The new technique is expected to benefit the electrical evaluation of fragile or soft materials along with LSI materials.
AB-BNCT beam shaping assembly based on 7Li(p,n)7Be reaction optimization
International Nuclear Information System (INIS)
A numerical optimization of a Beam Shaping Assembly (BSA) for Accelerator Based-Boron Neutron Capture Therapy (AB-BNCT) has been performed. The reaction 7Li(p,n)7Be has been considered using a proton beam on a lithium fluoride target. Proton energy and the dimensions of a simple BSA geometry have been varied to obtain a set of different configurations. The optimal configuration of this set is shown.
Robust design of broadband EUV multilayer beam splitters based on particle swarm optimization
International Nuclear Information System (INIS)
A robust design idea for broadband EUV multilayer beam splitters is introduced that achieves the aim of decreasing the influence of layer thickness errors on optical performances. Such beam splitters can be used in interferometry to determine the quality of EUVL masks by comparing with a reference multilayer. In the optimization, particle swarm techniques were used for the first time in such designs. Compared to conventional genetic algorithms, particle swarm optimization has stronger ergodicity, simpler processing and faster convergence
An optimized neutron-beam shaping assembly for accelerator-based BNCT
International Nuclear Information System (INIS)
Different materials and proton beam energies have been studied in order to search for an optimized neutron production target and beam shaping assembly for accelerator-based BNCT. The solution proposed in this work consists of successive stacks of Al, polytetrafluoroethylene, commercially known as Teflon[reg ], and LiF as moderator and neutron absorber, and Pb as reflector. This assembly is easy to build and its cost is relatively low. An exhaustive Monte Carlo simulation study has been performed evaluating the doses delivered to a Snyder model head phantom by a neutron production Li-metal target based on the 7Li(p,n)7Be reaction for proton bombarding energies of 1.92, 2.0, 2.3 and 2.5 MeV. Three moderator thicknesses have been studied and the figures of merit show the advantage of irradiating with near-resonance-energy protons (2.3 MeV) because of the relatively high neutron yield at this energy, which at the same time keeps the fast neutron healthy tissue dose limited and leads to the lowest treatment times. A moderator of 34 cm length has shown the best performance among the studied cases
International Nuclear Information System (INIS)
The design and simulation of a G-band extended interaction oscillator (EIO) driven by a pseudospark-sourced electron beam is presented. The characteristic of the EIO and the pseudospark-based electron beam were studied to enhance the performance of the newly proposed device. The beam-wave interaction of the EIO can be optimized by choosing a suitable pseudospark discharging voltage and by widening the operating voltage region of the EIO circuit. Simulation results show that a peak power of over 240 W can be achieved at G-band using a pseudospark discharge voltage of 41 kV
Optimal Design of Laminated Composite Beams
DEFF Research Database (Denmark)
Blasques, José Pedro Albergaria Amaral
This thesis presents an optimal design framework for the structural design of laminated composite beams. The possibility of improving the static and dynamic performance of laminated composite beam through the use of optimal design techniques motivates the investigation presented here. A structural...... model for the analysis of laminated composite beams is proposed. The structural analysis is performed in a beam finite element context. The development of a finite element based tool for the analysis of the cross section stiffness properties is described. The resulting beam finite element formulation is...... able to account for the effects of material anisotropy and inhomogeneity in the global response of the beam. Beam finite element models allow for a significant reduction in problem size and are therefore an efficient alternative in computationally intensive applications like optimization frameworks...
Beam shaping assembly optimization for 7Li(p,n)7Be accelerator based BNCT
International Nuclear Information System (INIS)
Within the framework of accelerator-based BNCT, a project to develop a folded Tandem-ElectroStatic-Quadrupole accelerator is under way at the Atomic Energy Commission of Argentina. The proposed accelerator is conceived to deliver a proton beam of 30 mA at about 2.5 MeV. In this work we explore a Beam Shaping Assembly (BSA) design based on the 7Li(p,n)7Be neutron production reaction to obtain neutron beams to treat deep seated tumors. - Highlights: • A Beam Shaping Assembly for accelerator based BNCT has been designed. • A conical port for easy patient positioning and the cooling system are included. • Several configurations can deliver tumor doses greater than 55 RBEGy. • Good tumor doses can be obtained in less than 60 min of irradiation time
Task-based modeling and optimization of a cone-beam CT scanner for musculoskeletal imaging
Energy Technology Data Exchange (ETDEWEB)
Prakash, P.; Zbijewski, W.; Gang, G. J.; Ding, Y.; Stayman, J. W.; Yorkston, J.; Carrino, J. A.; Siewerdsen, J. H. [Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 and Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5G 2 M9 (Canada); Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Carestream Health, Rochester, New York 14615 (United States); Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21287 (United States); Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland 21205 (United States); Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5G 2 M9 (Canada) and Department of Radiology, Johns Hopkins University, Baltimore, Maryland 21287 (United States)
2011-10-15
Purpose: This work applies a cascaded systems model for cone-beam CT imaging performance to the design and optimization of a system for musculoskeletal extremity imaging. The model provides a quantitative guide to the selection of system geometry, source and detector components, acquisition techniques, and reconstruction parameters. Methods: The model is based on cascaded systems analysis of the 3D noise-power spectrum (NPS) and noise-equivalent quanta (NEQ) combined with factors of system geometry (magnification, focal spot size, and scatter-to-primary ratio) and anatomical background clutter. The model was extended to task-based analysis of detectability index (d') for tasks ranging in contrast and frequency content, and d' was computed as a function of system magnification, detector pixel size, focal spot size, kVp, dose, electronic noise, voxel size, and reconstruction filter to examine trade-offs and optima among such factors in multivariate analysis. The model was tested quantitatively versus the measured NPS and qualitatively in cadaver images as a function of kVp, dose, pixel size, and reconstruction filter under conditions corresponding to the proposed scanner. Results: The analysis quantified trade-offs among factors of spatial resolution, noise, and dose. System magnification (M) was a critical design parameter with strong effect on spatial resolution, dose, and x-ray scatter, and a fairly robust optimum was identified at M {approx} 1.3 for the imaging tasks considered. The results suggested kVp selection in the range of {approx}65-90 kVp, the lower end (65 kVp) maximizing subject contrast and the upper end maximizing NEQ (90 kVp). The analysis quantified fairly intuitive results--e.g., {approx}0.1-0.2 mm pixel size (and a sharp reconstruction filter) optimal for high-frequency tasks (bone detail) compared to {approx}0.4 mm pixel size (and a smooth reconstruction filter) for low-frequency (soft-tissue) tasks. This result suggests a specific
Chao, Ming; Wei, Jie; Li, Tianfang; Yuan, Yading; Rosenzweig, Kenneth E.; Lo, Yeh-Chi
2016-04-01
We present a study of extracting respiratory signals from cone beam computed tomography (CBCT) projections within the framework of the Amsterdam Shroud (AS) technique. Acquired prior to the radiotherapy treatment, CBCT projections were preprocessed for contrast enhancement by converting the original intensity images to attenuation images with which the AS image was created. An adaptive robust z-normalization filtering was applied to further augment the weak oscillating structures locally. From the enhanced AS image, the respiratory signal was extracted using a two-step optimization approach to effectively reveal the large-scale regularity of the breathing signals. CBCT projection images from five patients acquired with the Varian Onboard Imager on the Clinac iX System Linear Accelerator (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique. Stable breathing signals can be reliably extracted using the proposed algorithm. Reference waveforms obtained using an air bellows belt (Philips Medical Systems, Cleveland, OH) were exported and compared to those with the AS based signals. The average errors for the enrolled patients between the estimated breath per minute (bpm) and the reference waveform bpm can be as low as -0.07 with the standard deviation 1.58. The new algorithm outperformed the original AS technique for all patients by 8.5% to 30%. The impact of gantry rotation on the breathing signal was assessed with data acquired with a Quasar phantom (Modus Medical Devices Inc., London, Canada) and found to be minimal on the signal frequency. The new technique developed in this work will provide a practical solution to rendering markerless breathing signal using the CBCT projections for thoracic and abdominal patients.
Chao, Ming; Wei, Jie; Li, Tianfang; Yuan, Yading; Rosenzweig, Kenneth E; Lo, Yeh-Chi
2016-04-21
We present a study of extracting respiratory signals from cone beam computed tomography (CBCT) projections within the framework of the Amsterdam Shroud (AS) technique. Acquired prior to the radiotherapy treatment, CBCT projections were preprocessed for contrast enhancement by converting the original intensity images to attenuation images with which the AS image was created. An adaptive robust z-normalization filtering was applied to further augment the weak oscillating structures locally. From the enhanced AS image, the respiratory signal was extracted using a two-step optimization approach to effectively reveal the large-scale regularity of the breathing signals. CBCT projection images from five patients acquired with the Varian Onboard Imager on the Clinac iX System Linear Accelerator (Varian Medical Systems, Palo Alto, CA) were employed to assess the proposed technique. Stable breathing signals can be reliably extracted using the proposed algorithm. Reference waveforms obtained using an air bellows belt (Philips Medical Systems, Cleveland, OH) were exported and compared to those with the AS based signals. The average errors for the enrolled patients between the estimated breath per minute (bpm) and the reference waveform bpm can be as low as -0.07 with the standard deviation 1.58. The new algorithm outperformed the original AS technique for all patients by 8.5% to 30%. The impact of gantry rotation on the breathing signal was assessed with data acquired with a Quasar phantom (Modus Medical Devices Inc., London, Canada) and found to be minimal on the signal frequency. The new technique developed in this work will provide a practical solution to rendering markerless breathing signal using the CBCT projections for thoracic and abdominal patients. PMID:27008349
International Nuclear Information System (INIS)
The study aims to introduce a hybrid optimization algorithm for anatomy-based intensity modulated radiotherapy (AB-IMRT). Our proposal is that by integrating an exact optimization algorithm with a heuristic optimization algorithm, the advantages of both the algorithms can be combined, which will lead to an efficient global optimizer solving the problem at a very fast rate. Our hybrid approach combines Gaussian elimination algorithm (exact optimizer) with fast simulated annealing algorithm (a heuristic global optimizer) for the optimization of beam weights in AB-IMRT. The algorithm has been implemented using MATLAB software. The optimization efficiency of the hybrid algorithm is clarified by (i) analysis of the numerical characteristics of the algorithm and (ii) analysis of the clinical capabilities of the algorithm. The numerical and clinical characteristics of the hybrid algorithm are compared with Gaussian elimination method (GEM) and fast simulated annealing (FSA). The numerical characteristics include convergence, consistency, number of iterations and overall optimization speed, which were analyzed for the respective cases of 8 patients. The clinical capabilities of the hybrid algorithm are demonstrated in cases of (a) prostate and (b) brain. The analyses reveal that (i) the convergence speed of the hybrid algorithm is approximately three times higher than that of FSA algorithm (ii) the convergence (percentage reduction in the cost function) in hybrid algorithm is about 20% improved as compared to that in GEM algorithm (iii) the hybrid algorithm is capable of producing relatively better treatment plans in terms of Conformity Index (CI) (∼ 2% - 5% improvement) and Homogeneity Index (HI) (∼ 4% - 10% improvement) as compared to GEM and FSA algorithms (iv) the sparing of organs at risk in hybrid algorithm-based plans is better than that in GEM-based plans and comparable to that in FSA-based plans; and (v) the beam weights resulting from the hybrid algorithm are
Spectrometer beam tube dimensional optimization
International Nuclear Information System (INIS)
This project examined the optimization of the design of a beam tube. An ANSYS model was used to find the minimum tube thickness and the best camber in a beam tube under vacuum and preloaded by a pair of magnet poles. After the tube was modeled one version of it was built for use in the accelerator. This beam tube was put under a vacuum and the dimensional changes were recorded and compared to the ANSYS predictions. These deflection results were quite close to the predicted numbers and would suggest that the stresses are similar to the predictions as well
International Nuclear Information System (INIS)
This study aims to evaluate the performance of a new algorithm for optimization of beam weights in anatomy-based intensity modulated radiotherapy (IMRT). The algorithm uses a numerical technique called Gaussian-Elimination that derives the optimum beam weights in an exact or non-iterative way. The distinct feature of the algorithm is that it takes only fraction of a second to optimize the beam weights, irrespective of the complexity of the given case. The algorithm has been implemented using MATLAB with a Graphical User Interface (GUI) option for convenient specification of dose constraints and penalties to different structures. We have tested the numerical and clinical capabilities of the proposed algorithm in several patient cases in comparison with KonRad inverse planning system. The comparative analysis shows that the algorithm can generate anatomy-based IMRT plans with about 50% reduction in number of MUs and 60% reduction in number of apertures, while producing dose distribution comparable to that of beamlet-based IMRT plans. Hence, it is clearly evident from the study that the proposed algorithm can be effectively used for clinical applications. (author)
An optimization-based method for geometrical calibration in cone-beam CT without dedicated phantoms
Panetta, D.; Belcari, N.; DelGuerra, A.; Moehrs, S.
2008-07-01
In this paper we present a new method for the determination of geometrical misalignments in cone-beam CT scanners, from the analysis of the projection data of a generic object. No a priori knowledge of the object shape and positioning is required. We show that a cost function, which depends on the misalignment parameters, can be defined using the projection data and that such a cost function has a local minimum in correspondence to the actual parameters of the system. Hence, the calibration of the scanner can be carried out by minimizing the cost function using standard optimization techniques. The method is developed for a particular class of 3D object functions, for which the redundancy of the fan beam sinogram in the transaxial midplane can be extended to cone-beam projection data, even at wide cone angles. The method has an approximated validity for objects which do not belong to that class; in that case, a suitable subset of the projection data can be selected in order to compute the cost function. We show by numerical simulations that our method is capable to determine with high accuracy the most critical misalignment parameters of the scanner, i.e., the transversal shift and the skew of the detector. Additionally, the detector slant can be determined. Other parameters such as the detector tilt, the longitudinal shift and the error in the source-detector distance cannot be determined with our method, as the proposed cost function has a very weak dependence on them. However, due to the negligible influence of these latter parameters in the reconstructed image quality, they can be kept fixed at estimated values in both calibration and reconstruction processes without compromising the final result. A trade-off between computational cost and calibration accuracy must be considered when choosing the data subset used for the computation of the cost function. Results on real data of a mouse femur as obtained with a small animal micro-CT are shown as well, proving
Atriana Palma, Bianey; Ureba Sánchez, Ana; Salguero, Francisco Javier; Arráns, Rafael; Míguez Sánchez, Carlos; Walls Zurita, Amadeo; Romero Hermida, María Isabel; Leal, Antonio
2012-03-01
The purpose of this study was to present a Monte-Carlo (MC)-based optimization procedure to improve conventional treatment plans for accelerated partial breast irradiation (APBI) using modulated electron beams alone or combined with modulated photon beams, to be delivered by a single collimation device, i.e. a photon multi-leaf collimator (xMLC) already installed in a standard hospital. Five left-sided breast cases were retrospectively planned using modulated photon and/or electron beams with an in-house treatment planning system (TPS), called CARMEN, and based on MC simulations. For comparison, the same cases were also planned by a PINNACLE TPS using conventional inverse intensity modulated radiation therapy (IMRT). Normal tissue complication probability for pericarditis, pneumonitis and breast fibrosis was calculated. CARMEN plans showed similar acceptable planning target volume (PTV) coverage as conventional IMRT plans with 90% of PTV volume covered by the prescribed dose (Dp). Heart and ipsilateral lung receiving 5% Dp and 15% Dp, respectively, was 3.2-3.6 times lower for CARMEN plans. Ipsilateral breast receiving 50% Dp and 100% Dp was an average of 1.4-1.7 times lower for CARMEN plans. Skin and whole body low-dose volume was also reduced. Modulated photon and/or electron beams planned by the CARMEN TPS improve APBI treatments by increasing normal tissue sparing maintaining the same PTV coverage achieved by other techniques. The use of the xMLC, already installed in the linac, to collimate photon and electron beams favors the clinical implementation of APBI with the highest efficiency.
Indian Academy of Sciences (India)
Saini R S; Tyagi Y; Ghodke A D; Puntambekar T A
2016-04-01
In this paper, we present the results of transverse beam emittance and twiss parameter measurement of an electron beam, delivered by a 20 MeV microtron which is used as a pre-injector system for a booster synchrotron in the Indus Accelerator Facility at RRCAT Indore. Based on these measured beam parameters, beam optics of a transport line was optimized and its results are alsodiscussed in this paper. This beam transport line is used to transport the electron beam from the 20MeV microtron to the booster synchrotron. The booster synchrotron works as a main injector for Indus-1 and Indus-2 synchrotron radiation facilities. To optimize the beam optics of a transport linefor proper beam transmission through the line as well as to match the beam twiss parameters at the beam injection point of another accelerator, it is necessary to know the transverse beam emittance and twiss parameters of the beam coming from the first one. A MATLAB-based GUI program has been developed to calculate the beam emittance and twiss parameters, using quadrupole scanmethod. The measured parameters have been used for beam transport line optimization and twiss parameters matching at booster injection point. After this optimization, an enhancement of ∼50% beam current has been observed in the booster synchrotron.
Two Effective Heuristics for Beam Angle Optimization in Radiation Therapy
Yarmand, Hamed
2013-01-01
In radiation therapy, mathematical methods have been used for optimizing treatment planning for delivery of sufficient dose to the cancerous cells while keeping the dose to critical surrounding structures minimal. This optimization problem can be modeled using mixed integer programming (MIP) whose solution gives the optimal beam orientation as well as optimal beam intensity. The challenge, however, is the computation time for this large scale MIP. We propose and investigate two novel heuristic approaches to reduce the computation time considerably while attaining high-quality solutions. We introduce a family of heuristic cuts based on the concept of 'adjacent beams' and a beam elimination scheme based on the contribution of each beam to deliver the dose to the tumor in the ideal plan in which all potential beams can be used simultaneously. We show the effectiveness of these heuristics for intensity modulated radiation therapy (IMRT) and stereotactic body radiation therapy (SBRT) on a clinical liver case.
Energy Technology Data Exchange (ETDEWEB)
Kurosu, Keita [Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 (Japan); Department of Radiation Oncology, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 (Japan); Takashina, Masaaki; Koizumi, Masahiko [Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871 (Japan); Das, Indra J. [Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN 46202 (United States); Moskvin, Vadim P., E-mail: vadim.p.moskvin@gmail.com [Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, IN 46202 (United States)
2014-10-01
Although three general-purpose Monte Carlo (MC) simulation tools: Geant4, FLUKA and PHITS have been used extensively, differences in calculation results have been reported. The major causes are the implementation of the physical model, preset value of the ionization potential or definition of the maximum step size. In order to achieve artifact free MC simulation, an optimized parameters list for each simulation system is required. Several authors have already proposed the optimized lists, but those studies were performed with a simple system such as only a water phantom. Since particle beams have a transport, interaction and electromagnetic processes during beam delivery, establishment of an optimized parameters-list for whole beam delivery system is therefore of major importance. The purpose of this study was to determine the optimized parameters list for GATE and PHITS using proton treatment nozzle computational model. The simulation was performed with the broad scanning proton beam. The influences of the customizing parameters on the percentage depth dose (PDD) profile and the proton range were investigated by comparison with the result of FLUKA, and then the optimal parameters were determined. The PDD profile and the proton range obtained from our optimized parameters list showed different characteristics from the results obtained with simple system. This led to the conclusion that the physical model, particle transport mechanics and different geometry-based descriptions need accurate customization in planning computational experiments for artifact-free MC simulation.
International Nuclear Information System (INIS)
Although three general-purpose Monte Carlo (MC) simulation tools: Geant4, FLUKA and PHITS have been used extensively, differences in calculation results have been reported. The major causes are the implementation of the physical model, preset value of the ionization potential or definition of the maximum step size. In order to achieve artifact free MC simulation, an optimized parameters list for each simulation system is required. Several authors have already proposed the optimized lists, but those studies were performed with a simple system such as only a water phantom. Since particle beams have a transport, interaction and electromagnetic processes during beam delivery, establishment of an optimized parameters-list for whole beam delivery system is therefore of major importance. The purpose of this study was to determine the optimized parameters list for GATE and PHITS using proton treatment nozzle computational model. The simulation was performed with the broad scanning proton beam. The influences of the customizing parameters on the percentage depth dose (PDD) profile and the proton range were investigated by comparison with the result of FLUKA, and then the optimal parameters were determined. The PDD profile and the proton range obtained from our optimized parameters list showed different characteristics from the results obtained with simple system. This led to the conclusion that the physical model, particle transport mechanics and different geometry-based descriptions need accurate customization in planning computational experiments for artifact-free MC simulation
Incorporating prior knowledge into beam orientation optimization in IMRT
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Purpose: Selection of beam configuration in currently available intensity-modulated radiotherapy (IMRT) treatment planning systems is still based on trial-and-error search. Computer beam orientation optimization has the potential to improve the situation, but its practical implementation is hindered by the excessive computing time associated with the calculation. The purpose of this work is to provide an effective means to speed up the beam orientation optimization by incorporating a priori geometric and dosimetric knowledge of the system and to demonstrate the utility of the new algorithm for beam placement in IMRT. Methods and Materials: Beam orientation optimization was performed in two steps. First, the quality of each possible beam orientation was evaluated using beam's-eye-view dosimetrics (BEVD) developed in our previous study. A simulated annealing algorithm was then employed to search for the optimal set of beam orientations, taking into account the BEVD scores of different incident beam directions. During the calculation, sampling of gantry angles was weighted according to the BEVD score computed before the optimization. A beam direction with a higher BEVD score had a higher probability of being included in the trial configuration, and vice versa. The inclusion of the BEVD weighting in the stochastic beam angle sampling process made it possible to avoid spending valuable computing time unnecessarily at 'bad' beam angles. An iterative inverse treatment planning algorithm was used for beam intensity profile optimization during the optimization process. The BEVD-guided beam orientation optimization was applied to an IMRT treatment of paraspinal tumor. The advantage of the new optimization algorithm was demonstrated by comparing the calculation with the conventional scheme without the BEVD weighting in the beam sampling. Results: The BEVD tool provided useful guidance for the selection of the potentially good directions for the beams to incident and was used
Optimizing the Natural Frequencies of Beams via Notch Stamping
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Nabeel T. Alshabatat
2012-07-01
Full Text Available Natural frequency optimization is important to avoid the coincidence of excitation frequency and natural frequency which causes resonance phenomenon. In this study, the natural frequencies of a beam, with different boundary conditions, are enhanced by stamping V-notches on its surface. These notches alter the local stiffness in the beam while keeping the mass the same. This method is cost-effective in comparison with other Structural Dynamics Modification methods (SDM because it is a one-step manufacturing method and because it enhances the dynamic behavior of beam structures without additional weight or additional joints. The natural frequencies of notched beam are calculated by finite element method. In particular, ANSYS package is used in building the notched beam models for modal analysis. The effect of notch location and size on the beam fundamental frequency is investigated. The simulation results indicated that creating notches on free-free beam decreases its fundamental frequency, while creating notches on clamped beam may increase its fundamental frequency. The optimal designs of notched beams are presented. The proposed method couples a finite element method for the modal analysis with an optimization technique based on Genetic Algorithm (GA. Three examples are presented to show the optimal design of free-free and clamped notched beams. The optimization results show that V-notch stamping technique is an effective technique to optimize the natural frequencies.
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We propose a new method for selecting importance factors (for regions of interest like organs at risk) used to plan conformal radiotherapy. Importance factors, also known as weighting factors or penalty factors, are essential in determining the relative importance of multiple objectives or the penalty ratios of constraints incorporated into cost functions, especially in dealing with dose optimization in radiotherapy treatment planning. Researchers usually choose importance factors on the basis of a trial-and-error process to reach a balance between all the objectives. In this study, we used a genetic algorithm and adopted a real-number encoding method to represent both beam weights and importance factors in each chromosome. The algorithm starts by optimizing the beam weights for a fixed number of iterations then modifying the importance factors for another fixed number of iterations. During the first phase, the genetic operators, such as crossover and mutation, are carried out only on beam weights, and importance factors for each chromosome are not changed or 'frozen'. In the second phase, the situation is reversed: the beam weights are 'frozen' and the importance factors are changed after crossover and mutation. Through alternation of these two phases, both beam weights and importance factors are adjusted according to a fitness function that describes the conformity of dose distribution in planning target volume and dose-tolerance constraints in organs at risk. Those chromosomes with better fitness are passed into the next generation, showing that they have a better combination of beam weights and importance factors. Although the ranges of the importance factors should be set in advance by using this algorithm, it is much more convenient than selecting specific numbers for importance factors. Three clinical examples are presented and compared with manual plans to verify this method. Three-dimensional standard displays and dose-volume histograms are shown to
Directory of Open Access Journals (Sweden)
Rahman WN
2014-05-01
.47. The dose enhancement factor obtained at other energy levels followed the same direction as the theoretical calculations based on the ratio of the mass energy absorption coefficients of gold and water. This experimental evidence shows that the radiosensitization effect of gold nanoparticles varies with photon energy as predicted from theoretical calculations. However, prediction based on theoretical assumptions is sometimes difficult due to the complexity of biological systems, so further study at the cellular level is required to fully characterize the effects of gold nanoparticles with ionizing radiation.Keywords: gold nanoparticles, radiotherapy, monoenergetic synchrotron radiation, radiosensitizers, in vitro
Optimization approaches for planning external beam radiotherapy
Gozbasi, Halil Ozan
Cancer begins when cells grow out of control as a result of damage to their DNA. These abnormal cells can invade healthy tissue and form tumors in various parts of the body. Chemotherapy, immunotherapy, surgery and radiotherapy are the most common treatment methods for cancer. According to American Cancer Society about half of the cancer patients receive a form of radiation therapy at some stage. External beam radiotherapy is delivered from outside the body and aimed at cancer cells to damage their DNA making them unable to divide and reproduce. The beams travel through the body and may damage nearby healthy tissue unless carefully planned. Therefore, the goal of treatment plan optimization is to find the best system parameters to deliver sufficient dose to target structures while avoiding damage to healthy tissue. This thesis investigates optimization approaches for two external beam radiation therapy techniques: Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT). We develop automated treatment planning technology for IMRT that produces several high-quality treatment plans satisfying provided clinical requirements in a single invocation and without human guidance. A novel bi-criteria scoring based beam selection algorithm is part of the planning system and produces better plans compared to those produced using a well-known scoring-based algorithm. Our algorithm is very efficient and finds the beam configuration at least ten times faster than an exact integer programming approach. Solution times range from 2 minutes to 15 minutes which is clinically acceptable. With certain cancers, especially lung cancer, a patient's anatomy changes during treatment. These anatomical changes need to be considered in treatment planning. Fortunately, recent advances in imaging technology can provide multiple images of the treatment region taken at different points of the breathing cycle, and deformable image registration algorithms can
Automated beam steering using optimal control
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We present a steering algorithm which, with the aid of a model, allows the user to specify beam behavior throughout a beamline, rather than just at specified beam position monitor (BPM) locations. The model is used primarily to compute the values of the beam phase vectors from BPM measurements, and to define cost functions that describe the steering objectives. The steering problem is formulated as constrained optimization problem; however, by applying optimal control theory we can reduce it to an unconstrained optimization whose dimension is the number of control signals.
Modeling and design of a cone-beam CT head scanner using task-based imaging performance optimization
Xu, J.; Sisniega, A.; Zbijewski, W.; Dang, H.; Stayman, J. W.; Wang, X.; Foos, D. H.; Aygun, N.; Koliatsos, V. E.; Siewerdsen, J. H.
2016-04-01
Detection of acute intracranial hemorrhage (ICH) is important for diagnosis and treatment of traumatic brain injury, stroke, postoperative bleeding, and other head and neck injuries. This paper details the design and development of a cone-beam CT (CBCT) system developed specifically for the detection of low-contrast ICH in a form suitable for application at the point of care. Recognizing such a low-contrast imaging task to be a major challenge in CBCT, the system design began with a rigorous analysis of task-based detectability including critical aspects of system geometry, hardware configuration, and artifact correction. The imaging performance model described the three-dimensional (3D) noise-equivalent quanta using a cascaded systems model that included the effects of scatter, scatter correction, hardware considerations of complementary metal-oxide semiconductor (CMOS) and flat-panel detectors (FPDs), and digitization bit depth. The performance was analyzed with respect to a low-contrast (40-80 HU), medium-frequency task representing acute ICH detection. The task-based detectability index was computed using a non-prewhitening observer model. The optimization was performed with respect to four major design considerations: (1) system geometry (including source-to-detector distance (SDD) and source-to-axis distance (SAD)); (2) factors related to the x-ray source (including focal spot size, kVp, dose, and tube power); (3) scatter correction and selection of an antiscatter grid; and (4) x-ray detector configuration (including pixel size, additive electronics noise, field of view (FOV), and frame rate, including both CMOS and a-Si:H FPDs). Optimal design choices were also considered with respect to practical constraints and available hardware components. The model was verified in comparison to measurements on a CBCT imaging bench as a function of the numerous design parameters mentioned above. An extended geometry (SAD = 750 mm, SDD = 1100
Xu, J; Sisniega, A; Zbijewski, W; Dang, H; Stayman, J W; Wang, X; Foos, D H; Aygun, N; Koliatsos, V E; Siewerdsen, J H
2016-04-21
Detection of acute intracranial hemorrhage (ICH) is important for diagnosis and treatment of traumatic brain injury, stroke, postoperative bleeding, and other head and neck injuries. This paper details the design and development of a cone-beam CT (CBCT) system developed specifically for the detection of low-contrast ICH in a form suitable for application at the point of care. Recognizing such a low-contrast imaging task to be a major challenge in CBCT, the system design began with a rigorous analysis of task-based detectability including critical aspects of system geometry, hardware configuration, and artifact correction. The imaging performance model described the three-dimensional (3D) noise-equivalent quanta using a cascaded systems model that included the effects of scatter, scatter correction, hardware considerations of complementary metal-oxide semiconductor (CMOS) and flat-panel detectors (FPDs), and digitization bit depth. The performance was analyzed with respect to a low-contrast (40-80 HU), medium-frequency task representing acute ICH detection. The task-based detectability index was computed using a non-prewhitening observer model. The optimization was performed with respect to four major design considerations: (1) system geometry (including source-to-detector distance (SDD) and source-to-axis distance (SAD)); (2) factors related to the x-ray source (including focal spot size, kVp, dose, and tube power); (3) scatter correction and selection of an antiscatter grid; and (4) x-ray detector configuration (including pixel size, additive electronics noise, field of view (FOV), and frame rate, including both CMOS and a-Si:H FPDs). Optimal design choices were also considered with respect to practical constraints and available hardware components. The model was verified in comparison to measurements on a CBCT imaging bench as a function of the numerous design parameters mentioned above. An extended geometry (SAD = 750 mm, SDD = 1100
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Purpose: To verify the potential of aperture-based intensity-modulated radiotherapy (AB-IMRT) to realize dose escalation plans for non-preselected non-small-cell lung cancer (NSCLC) patients, using photon beam energy optimization. Methods and materials: Seven cases of NSCLC were retrospectively studied. Clinical reference plans were made at 60 Gy by an experienced dosimetrist. Dose escalation was applied to PTV2, a subvolume within the main PTV1. Escalation plans were optimized by considering beam angles (table and gantry), energy (6 and 23 MV) and weights, for an increasing dose to the PTV2, starting from 66 Gy and keeping 30 fractions. Results: In five cases, doses over 78 Gy could be achieved before exceeding organs at risk (OARs) standard tolerance. Peripheral overdosages, as well as lung and spinal cord tolerance doses, limited escalation. Means ± SD V95% parameters were (97.3 ± 0.9)% for PTV1s and (96.7 ± 2.2)% for PTV2s. Doses to OARs were also maintained at acceptable levels. Optimized plans made use of both low- and high-energy beams and had a similar number of monitor units compared to the 60 Gy clinical plans. Conclusions: The AB-IMRT system can successfully realize dose escalation for a sizeable number of cases. Plans produced contained few large segments, and are applicable to a wide range of tumor volumes and locations.
Optimization of combined electron and photon beams for breast cancer
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Recently, intensity-modulated radiation therapy and modulated electron radiotherapy have gathered a growing interest for the treatment of breast and head and neck tumours. In this work, we carried out a study to combine electron and photon beams to achieve differential dose distributions for multiple target volumes simultaneously. A Monte Carlo based treatment planning system was investigated, which consists of a set of software tools to perform accurate dose calculation, treatment optimization, leaf sequencing and plan analysis. We compared breast treatment plans generated using this home-grown optimization and dose calculation software for different treatment techniques. Five different planning techniques have been developed for this study based on a standard photon beam whole breast treatment and an electron beam tumour bed cone down. Technique 1 includes two 6 MV tangential wedged photon beams followed by an anterior boost electron field. Technique 2 includes two 6 MV tangential intensity-modulated photon beams and the same boost electron field. Technique 3 optimizes two intensity-modulated photon beams based on a boost electron field. Technique 4 optimizes two intensity-modulated photon beams and the weight of the boost electron field. Technique 5 combines two intensity-modulated photon beams with an intensity-modulated electron field. Our results show that technique 2 can reduce hot spots both in the breast and the tumour bed compared to technique 1 (dose inhomogeneity is reduced from 34% to 28% for the target). Techniques 3, 4 and 5 can deliver a more homogeneous dose distribution to the target (with dose inhomogeneities for the target of 22%, 20% and 9%, respectively). In many cases techniques 3, 4 and 5 can reduce the dose to the lung and heart. It is concluded that combined photon and electron beam therapy may be advantageous for treating breast cancer compared to conventional treatment techniques using tangential wedged photon beams followed by a boost
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We investigate the design for a scattering with angular limitation in projection electron-beam lithography (SCALPEL) based electron projection system with a demagnification of -4. By a ''field-flip'' process we can construct a doublet in which the magnetic field has a flat feature in most of the optic column but opposite sign at two sides connected by a sharp transition region. Such a theoretical model can give a near zero chromatic aberration of rotation and much smaller field curvature and astigmatism. Compared with the conventional doublet, the total image blur caused by aberrations at 1/√(2) mm off-axis distance and 1.5 mrad semiangle aperture at the mask side is about only 24 nm for a column length of 400 mm. A shorter column, less than the current 400 mm, is also favored for further reducing the total aberration. These guarantee that we can choose a much larger aperture angle (compared with present 0.5 mrad) and beam current density in such a SCALPEL projection system to achieve higher throughput while still maintaining current resolution. A practical issue for possible magnetic lens design is also discussed. (c) 2000 American Vacuum Society
Uncertainty incorporated beam angle optimization for IMPT treatment planning
Cao, Wenhua; Gino J. Lim; Lee, Andrew; Li, Yupeng; Liu, Wei; Ronald Zhu, X.; Zhang, Xiaodong
2012-01-01
Purpose: Beam angle optimization (BAO) by far remains an important and challenging problem in external beam radiation therapy treatment planning. Conventional BAO algorithms discussed in previous studies all focused on photon-based therapies. Impact of BAO on proton therapy is important while proton therapy increasingly receives great interests. This study focuses on potential benefits of BAO on intensity-modulated proton therapy (IMPT) that recently began available to clinical cancer treatment.
Mishra, Sanjay; Yadava, Vinod
2013-06-01
The creation of small diameter holes in thin sheets (Drilling (LBPD) process. First, a 2D axisymmetric FEM-based thermal model for LBPD has been developed incorporating temperature-dependent thermal properties, optical properties and phase change phenomena of the sheet material. The developed FEM-based thermal model is validated with self-conducted experimental results in terms of hole taper which is further used to generate adequate input and output data for training and testing of the ANN model. Gray Relational Analysis (GRA) coupled with Principal Component Analysis (PCA) has been effectively used for the multi-objective optimization of the LBPD process utilizing the data predicted by the trained ANN model. The developed ANN model has been used to predict the performance characteristics of the LBPD process. The results predicted by the ANN model show that with the increase in pulse width and peak power the hole taper, material removal rate (MRR) and heat-affected zone (HAZ) increases. The acquired combination of optimal process variables produce a hole with good integral quality, i.e., a reduction of hole taper by 32.1%, increase of material removal rate by 28.9% and reduction of extent of HAZ by 4.5%.
Optimization of electron beam crosslinking of wire and cable insulation
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The computer simulations based on Monte Carlo (MC) method and the ModeCEB software were carried out in connection with electron beam (EB) radiation set-up for crosslinking of electric wire and cable insulation. The theoretical predictions for absorbed dose distribution in irradiated electric insulation induced by scanned EB were compared to the experimental results of irradiation that was carried out in the experimental set-up based on ILU 6 electron accelerator with electron energy 0.5–2.0 MeV. The computer simulation of the dose distributions in two-sided irradiation system by a scanned electron beam in multilayer circular objects was performed for various process parameters, namely electric wire and cable geometry (thickness of insulation layers and copper wire diameter), type of polymer insulation, electron energy, energy spread and geometry of electron beam, electric wire and cable layout in irradiation zone. The geometry of electron beam distribution in the irradiation zone was measured using CTA and PVC foil dosimeters for available electron energy range. The temperature rise of the irradiated electric wire and irradiation homogeneity were evaluated for different experimental conditions to optimize technological process parameters. The results of computer simulation are consistent with the experimental data of dose distribution evaluated by gel-fraction measurements. Such conformity indicates that ModeCEB computer simulation is reliable and sufficient for optimization absorbed dose distribution in the multi-layer circular objects irradiated with scanned electron beams. - Highlights: ► We model wire and cables irradiation process by Monte Carlo simulations. ► We optimize irradiation configuration for various process parameters. ► Temperature rise and irradiation homogeneity were evaluated. ► Calculation (dose) and experimental (gel-fraction) results were compared. ► Computer simulation was found reliable and sufficient for process optimization.
Optimization of atomic beam sources for polarization experiments
Energy Technology Data Exchange (ETDEWEB)
Gaisser, Martin; Nass, Alexander; Stroeher, Hans [IKP, Forschungszentrum Juelich (Germany)
2013-07-01
For experiments with spin-polarized protons and neutrons a dense target is required. In current atomic beam sources an atomic hydrogen or deuterium beam is expanded through a cold nozzle and a system of sextupole magnets and RF-transition units selects a certain hyperfine state. The achievable flux seems to be limited to about 10{sup 17} particles per second with a high nuclear polarization. A lot of experimental and theoretical effort has been undertaken to understand all effects and to increase the flux. However, improvements have remained marginal. Now, a Monte Carlo simulation based on the DSMC part of the open source C++ library OpenFOAM is set up in order to get a better understanding of the flow and to optimize the various elements. It is intended to include important effects like deflection from magnetic fields, recombination on the walls and spin exchange collisions in the simulation and make quantitative predictions of changes in the experimental setup. The goal is to get a tool that helps to further increase the output of an atomic beam source. So far, a new binary collision model, magnetic fields, RF-transition units and a tool to measure the collision age are included. The next step will be to couple the whole simulation with an optimization algorithm implementing Adaptive Simulated Annealing (ASA) in order to automatically optimize the atomic beam source.
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Automatic beam angle selection is an important but challenging problem for intensity-modulated radiation therapy (IMRT) planning. Though many efforts have been made, it is still not very satisfactory in clinical IMRT practice because of overextensive computation of the inverse problem. In this paper, a new technique named BASPSO (Beam Angle Selection with a Particle Swarm Optimization algorithm) is presented to improve the efficiency of the beam angle optimization problem. Originally developed as a tool for simulating social behaviour, the particle swarm optimization (PSO) algorithm is a relatively new population-based evolutionary optimization technique first introduced by Kennedy and Eberhart in 1995. In the proposed BASPSO, the beam angles are optimized using PSO by treating each beam configuration as a particle (individual), and the beam intensity maps for each beam configuration are optimized using the conjugate gradient (CG) algorithm. These two optimization processes are implemented iteratively. The performance of each individual is evaluated by a fitness value calculated with a physical objective function. A population of these individuals is evolved by cooperation and competition among the individuals themselves through generations. The optimization results of a simulated case with known optimal beam angles and two clinical cases (a prostate case and a head-and-neck case) show that PSO is valid and efficient and can speed up the beam angle optimization process. Furthermore, the performance comparisons based on the preliminary results indicate that, as a whole, the PSO-based algorithm seems to outperform, or at least compete with, the GA-based algorithm in computation time and robustness. In conclusion, the reported work suggested that the introduced PSO algorithm could act as a new promising solution to the beam angle optimization problem and potentially other optimization problems in IMRT, though further studies need to be investigated
Optimization of Natural Frequencies and Sound Power of Beams Using Functionally Graded Material
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Nabeel T. Alshabatat
2014-01-01
Full Text Available This paper presents a design method to optimize the material distribution of functionally graded beams with respect to some vibration and acoustic properties. The change of the material distribution through the beam length alters the stiffness and the mass of the beam. This can be used to alter a specific beam natural frequency. It can also be used to reduce the sound power radiated from the vibrating beam. Two novel volume fraction laws are used to describe the material volume distributions through the length of the FGM beam. The proposed method couples the finite element method (for the modal and harmonic analysis, Lumped Parameter Model (for calculating the power of sound radiation, and an optimization technique based on Genetic Algorithm. As a demonstration of this technique, the optimization procedure is applied to maximize the fundamental frequency of FGM cantilever and clamped beams and to minimize the sound radiation from vibrating clamped FGM beam at a specific frequency.
Optimized Beam Sculpting with Generalized Fringe-Rate Filters
Parsons, Aaron R; Ali, Zaki S; Cheng, Carina
2015-01-01
We generalize the technique of fringe-rate filtering, whereby visibilities measured by a radio interferometer are re-weighted according to their temporal variation. As the Earth rotates, radio sources traverse through an interferometer's fringe pattern at rates that depend on their position on the sky. Capitalizing on this geometric interpretation of fringe rates, we employ time-domain convolution kernels to enact fringe-rate filters that sculpt the effective primary beam of antennas in an interferometer. As we show, beam sculpting through fringe-rate filtering can be used to optimize measurements for a variety of applications, including mapmaking, minimizing polarization leakage, suppressing instrumental systematics, and enhancing the sensitivity of power-spectrum measurements. We show that fringe-rate filtering arises naturally in minimum variance treatments of many of these problems, enabling optimal visibility-based approaches to analyses of interferometric data that avoid systematics potentially introduc...
Beam Delivery Simulation: BDSIM - Development & Optimization
Nevay, Laurence James; Garcia-Morales, H; Gibson, S M; Kwee-Hinzmann, R; Snuverink, J; Deacon, L C
2014-01-01
Beam Delivery Simulation (BDSIM) is a Geant4 and C++ based particle tracking code that seamlessly tracks particles through accelerators and detectors, including the full range of particle interaction physics processes from Geant4. BDSIM has been successfully used to model beam loss and background conditions for many current and future linear accelerators such as the Accelerator Test Facility 2 (ATF2) and the International Linear Collider (ILC). Current developments extend its application for use with storage rings, in particular for the Large Hadron Collider (LHC) and the High Luminosity upgrade project (HL-LHC). This paper presents the latest results from using BDSIM to model the LHC as well as the developments underway to improve performance.
Energy Technology Data Exchange (ETDEWEB)
Huang, B-T; Lu, J-Y [Cancer Hospital of Shantou University Medical College, Shantou (China)
2015-06-15
Purpose: To optimize the flattening filter free (FFF) beam energy selection in stereotactic body radiotherapy (SBRT) treatment for stage I lung cancer with different fraction schemes. Methods: Twelve patients suffering from stage I lung cancer were enrolled in this study. Plans were designed using 6XFFF and 10XFFF beams with the most widely used fraction schemes of 4*12 Gy, 3*18 Gy and 1*34 Gy, respectively. The plan quality was appraised in terms of planning target volume (PTV) coverage, conformity of the prescribed dose (CI100%), intermediate dose spillage (R50% and D2cm), organs at risk (OARs) sparing and beam-on time. Results: The 10XFFF beam predicted 1% higher maximum, mean dose to the PTV and 4–5% higher R50% compared with the 6XFFF beam in the three fraction schemes, whereas the CI100% and D2cm was similar. Most importantly, the 6XFFF beam exhibited 3–10% lower dose to all the OARs. However, the 10XFFF beam reduced the beam-on time by 31.9±7.2%, 38.7±2.8% and 43.6±4.0% compared with the 6XFFF beam in the 4*12 Gy, 3*18 Gy and 1*34 Gy schemes, respectively. Beam-on time was 2.2±0.2 vs 1.5±0.1, 3.3±0.9 vs 2.0±0.5 and 6.3±0.9 vs 3.5±0.4 minutes for the 6XFFF and 10XFFF one in the three fraction schemes. Conclusion: The 6XFFF beam obtains better OARs sparing in SBRT treatment for stage I lung cancer, but the 10XFFF one provides improved treatment efficiency. To balance the OARs sparing and intrafractional variation as a function of prolonged treatment time, the authors recommend to use the 6XFFF beam in the 4*12 Gy and 3*18 Gy schemes for better OARs sparing. However, for the 1*34 Gy scheme, the 10XFFF beam is recommended to achieve improved treatment efficiency.
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Purpose: To optimize the flattening filter free (FFF) beam energy selection in stereotactic body radiotherapy (SBRT) treatment for stage I lung cancer with different fraction schemes. Methods: Twelve patients suffering from stage I lung cancer were enrolled in this study. Plans were designed using 6XFFF and 10XFFF beams with the most widely used fraction schemes of 4*12 Gy, 3*18 Gy and 1*34 Gy, respectively. The plan quality was appraised in terms of planning target volume (PTV) coverage, conformity of the prescribed dose (CI100%), intermediate dose spillage (R50% and D2cm), organs at risk (OARs) sparing and beam-on time. Results: The 10XFFF beam predicted 1% higher maximum, mean dose to the PTV and 4–5% higher R50% compared with the 6XFFF beam in the three fraction schemes, whereas the CI100% and D2cm was similar. Most importantly, the 6XFFF beam exhibited 3–10% lower dose to all the OARs. However, the 10XFFF beam reduced the beam-on time by 31.9±7.2%, 38.7±2.8% and 43.6±4.0% compared with the 6XFFF beam in the 4*12 Gy, 3*18 Gy and 1*34 Gy schemes, respectively. Beam-on time was 2.2±0.2 vs 1.5±0.1, 3.3±0.9 vs 2.0±0.5 and 6.3±0.9 vs 3.5±0.4 minutes for the 6XFFF and 10XFFF one in the three fraction schemes. Conclusion: The 6XFFF beam obtains better OARs sparing in SBRT treatment for stage I lung cancer, but the 10XFFF one provides improved treatment efficiency. To balance the OARs sparing and intrafractional variation as a function of prolonged treatment time, the authors recommend to use the 6XFFF beam in the 4*12 Gy and 3*18 Gy schemes for better OARs sparing. However, for the 1*34 Gy scheme, the 10XFFF beam is recommended to achieve improved treatment efficiency
ATF neutral beam injection: optimization of beam alignment and aperturing
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The application of the existing Impurity Study Experiment (ISX-B) neutral beam injectors for the Advanced Toroidal Facility (ATF) is studied. It is determined that with the practical considerations of beam aperturing, ATF vacuum vessel complexity, and realistic beam modeling, the power absorbed by the plasma will be approximately 57% of the extracted neutral beam power, which corresponds to an injected power of about 1.5 MW. By reducing the beam divergence to a 10 Gaussian distribution, the absorbed power could be increased to 93%. The power delivered to the plasma is found to be a strong function of the beam divergence but only a weak function of the beam focal length. Shinethrough can be a serious problem if very low density startups are necessary. Preliminary calculations indicate that there will be no excessive fast-ion losses. 12 refs., 17 figs., 1 tab
Aspects on the optimal photon beam energy for radiation therapy
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The selection of optimal photon beam energy is investigated both for realistic clinical bremsstrahlung beams and for monoenergetic photon beams. The photon energies covered in this investigation range from 60Co to bremsstrahlung and monoenergetic beams with maximum energies up to 50 MeV. One head and neck tumor and an advanced cervix tumor are investigated and the influence of beam direction is considered. It is shown that the use of optimized intensity modulated photon beams significantly reduces the need of beam energy selection. The most suitable single accelerator potential will generally be in the range 6-15 MV for both superficially located and deep-seated targets, provided intensity-modulated dose delivery is employed. It is also shown that a narrow penumbra region of a photon beam ideally should contain low-energy photons (≤4 MV), whereas the gross tumor volume, particularly when deep-seated targets are concerned, should be irradiated by high-energy photons. The regions where low photon energies are most beneficial are where organs at risk are laterally close to the target volume. The situation is completely changed when uniform or wedged beams are used. The selection of optimal beam energy then becomes a very important task in line with the experience from traditional treatment techniques. However, even with a large number of uniform beam portals, the treatment outcome is substantially lower than with a few optimized intensity-modulated beams. (orig.)
Fast optimization and dose calculation in scanned ion beam therapy
Energy Technology Data Exchange (ETDEWEB)
Hild, S. [Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Department of Radiation Oncology, University Clinic Erlangen and Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen (Germany); Institute for Medical Physics and Radiation Protection, University of Applied Sciences, 35390 Giessen (Germany); Graeff, C.; Trautmann, J.; Kraemer, M. [Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64289 Darmstadt (Germany); Zink, K. [Institute for Medical Physics and Radiation Protection, University of Applied Sciences, 35390 Giessen, Germany and Department of Radiotherapy and Radiooncology, University Hospital Giessen-Marburg, 35043 Marburg (Germany); Durante, M. [Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64289 Darmstadt, Germany and Faculty of Physics, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Bert, C., E-mail: christoph.bert@uk-erlangen.de [Department of Biophysics, GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64289 Darmstadt, Germany and Department of Radiation Oncology, University Clinic Erlangen and Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 91054 Erlangen (Germany)
2014-07-15
Purpose: Particle therapy (PT) has advantages over photon irradiation on static tumors. An increased biological effectiveness and active target conformal dose shaping are strong arguments for PT. However, the sensitivity to changes of internal geometry complicates the use of PT for moving organs. In case of interfractionally moving objects adaptive radiotherapy (ART) concepts known from intensity modulated radiotherapy (IMRT) can be adopted for PT treatments. One ART strategy is to optimize a new treatment plan based on daily image data directly before a radiation fraction is delivered [treatment replanning (TRP)]. Optimizing treatment plans for PT using a scanned beam is a time consuming problem especially for particles other than protons where the biological effective dose has to be calculated. For the purpose of TRP, fast optimization and fast dose calculation have been implemented into the GSI in-house treatment planning system (TPS) TRiP98. Methods: This work reports about the outcome of a code analysis that resulted in optimization of the calculation processes as well as implementation of routines supporting parallel execution of the code. To benchmark the new features, the calculation time for therapy treatment planning has been studied. Results: Compared to the original version of the TPS, calculation times for treatment planning (optimization and dose calculation) have been improved by a factor of 10 with code optimization. The parallelization of the TPS resulted in a speedup factor of 12 and 5.5 for the original version and the code optimized version, respectively. Hence the total speedup of the new implementation of the authors' TPS yielded speedup factors up to 55. Conclusions: The improved TPS is capable of completing treatment planning for ion beam therapy of a prostate irradiation considering organs at risk in this has been overseen in the review process. Also see below 6 min.
Fast optimization and dose calculation in scanned ion beam therapy
International Nuclear Information System (INIS)
Purpose: Particle therapy (PT) has advantages over photon irradiation on static tumors. An increased biological effectiveness and active target conformal dose shaping are strong arguments for PT. However, the sensitivity to changes of internal geometry complicates the use of PT for moving organs. In case of interfractionally moving objects adaptive radiotherapy (ART) concepts known from intensity modulated radiotherapy (IMRT) can be adopted for PT treatments. One ART strategy is to optimize a new treatment plan based on daily image data directly before a radiation fraction is delivered [treatment replanning (TRP)]. Optimizing treatment plans for PT using a scanned beam is a time consuming problem especially for particles other than protons where the biological effective dose has to be calculated. For the purpose of TRP, fast optimization and fast dose calculation have been implemented into the GSI in-house treatment planning system (TPS) TRiP98. Methods: This work reports about the outcome of a code analysis that resulted in optimization of the calculation processes as well as implementation of routines supporting parallel execution of the code. To benchmark the new features, the calculation time for therapy treatment planning has been studied. Results: Compared to the original version of the TPS, calculation times for treatment planning (optimization and dose calculation) have been improved by a factor of 10 with code optimization. The parallelization of the TPS resulted in a speedup factor of 12 and 5.5 for the original version and the code optimized version, respectively. Hence the total speedup of the new implementation of the authors' TPS yielded speedup factors up to 55. Conclusions: The improved TPS is capable of completing treatment planning for ion beam therapy of a prostate irradiation considering organs at risk in this has been overseen in the review process. Also see below 6 min
Jędrzejowicz, Piotr; Kacprzyk, Janusz
2013-01-01
This volume presents a collection of original research works by leading specialists focusing on novel and promising approaches in which the multi-agent system paradigm is used to support, enhance or replace traditional approaches to solving difficult optimization problems. The editors have invited several well-known specialists to present their solutions, tools, and models falling under the common denominator of the agent-based optimization. The book consists of eight chapters covering examples of application of the multi-agent paradigm and respective customized tools to solve difficult optimization problems arising in different areas such as machine learning, scheduling, transportation and, more generally, distributed and cooperative problem solving.
Optimal beam quality for chest digital radiography
International Nuclear Information System (INIS)
To investigate the optimal beam quality for chest computed radiography (CR), we measured the radiographic contrast and evaluated the image quality of chest CR using various X-ray tube voltages. The constant between lung and rib or heart increased on CR image obtained by lowering the tube voltage from 140 to 60 kV, but the degree of increase was less. Scattered radiation was reduced on CR images with a lower tube voltage. The Wiener spectrum of CR images with a low tube voltage showed a low value under identical conditions of amount of light stimulated emission. The quality of chest CR image obtained using a lower tube voltage (80 kV and 100 kV) was evaluated as being superior to those obtained with a higher tube voltage (120 kV and 140 kV). Considering the problem of tube loading and exposure in clinical applications, a tube voltage of 90 to 100 kV (0.1 mm copper filter backed by 0.5 mm aluminum) is recommended for chest CR. (author)
Improved genetic algorithm in optimization of beam orientation in intensity modulated radiotherapy
International Nuclear Information System (INIS)
Objective: At present beam orientation selection in intensity-modulated radiotherapy (IMRT) is mainly based on empiric knowledge. This study is to evaluate the feasibility of automated beam angle selection. Methods: Genetic algorithm technique which based on beam eye view dose measurement (BEVD-GA) was tested on two clinical cases, including a spine column cancer and a lung cancer. Three plans were obtained under the following different beam configurations: five equiangular-spaced beams, five beams with GA-selected, and five beams with BEVD-GA-selected beams. Then the dose distribution was compared among the three plans. Results: The method, restricting the range of genetic algorithm followed by carrying through genetic operations, not only shortened the optimization time, but also improved the optimization effect. For spine column cancer and lung cancer, the best IMRT plans were obtained with BEVD-GA-selected beams, which used automated beam orientation selection. Conclusions: Comparing with the conventional manual beam orientation selection, beam orientation optimization which is feasible in IMRT planning may significantly improve the efficiency and result. (authors)
Submicron accuracy optimization for laser beam soldering processes
Beckert, Erik; Burkhardt, Thomas; Hornaff, Marcel; Kamm, Andreas; Scheidig, Ingo; Stiehl, Cornelia; Eberhardt, Ramona; Tünnermann, Andreas
2010-02-01
Laser beam soldering is a packaging technology alternative to polymeric adhesive bonding in terms of stability and functionality. Nevertheless, when packaging especially micro optical and MOEMS systems this technology has to fulfil stringent requirements for accuracy in the micron and submicron range. Investigating the assembly of several laser optical systems it has been shown that micron accuracy and submicron reproducibility can be reached when using design-of-experiment optimized solder processes that are based on applying liquid solder drops ("Solder Bumping") onto wettable metalized joining surfaces of optical components. The soldered assemblies were subject to thermal cycles and vibration/ shock test also.
Kurosu, Keita; Das, Indra J.; Moskvin, Vadim P.
2016-01-01
Spot scanning, owing to its superior dose-shaping capability, provides unsurpassed dose conformity, in particular for complex targets. However, the robustness of the delivered dose distribution and prescription has to be verified. Monte Carlo (MC) simulation has the potential to generate significant advantages for high-precise particle therapy, especially for medium containing inhomogeneities. However, the inherent choice of computational parameters in MC simulation codes of GATE, PHITS and FLUKA that is observed for uniform scanning proton beam needs to be evaluated. This means that the relationship between the effect of input parameters and the calculation results should be carefully scrutinized. The objective of this study was, therefore, to determine the optimal parameters for the spot scanning proton beam for both GATE and PHITS codes by using data from FLUKA simulation as a reference. The proton beam scanning system of the Indiana University Health Proton Therapy Center was modeled in FLUKA, and the geometry was subsequently and identically transferred to GATE and PHITS. Although the beam transport is managed by spot scanning system, the spot location is always set at the center of a water phantom of 600 × 600 × 300 mm3, which is placed after the treatment nozzle. The percentage depth dose (PDD) is computed along the central axis using 0.5 × 0.5 × 0.5 mm3 voxels in the water phantom. The PDDs and the proton ranges obtained with several computational parameters are then compared to those of FLUKA, and optimal parameters are determined from the accuracy of the proton range, suppressed dose deviation, and computational time minimization. Our results indicate that the optimized parameters are different from those for uniform scanning, suggesting that the gold standard for setting computational parameters for any proton therapy application cannot be determined consistently since the impact of setting parameters depends on the proton irradiation technique. We
Beam-Based Procedures for RF Guns
Krasilnikov, Mikhail; Grabosch, H J; Hartrott, Michael; Hui Han, Jang; Miltchev, Velizar; Oppelt, Anne; Petrosyan, Bagrat; Staykov, Lazar; Stephan, Frank
2005-01-01
A wide range of rf photo injector parameters has to be optimized in order to achieve an electron source performance as required for linac based high gain FELs. Some of the machine parameters can not be precisely controlled by direct measurements, whereas the tolerance on them is extremely tight. Therefore, this should be met with beam-based techniques. Procedures for beam-based alignment (BBA) of the laser on the photo cathode as well as solenoid alignment have been developed. They were applied at the Photo Injector Test facility at DESY Zeuthen (PITZ) and at the photo injector of the VUV-FEL at DESY Hamburg. A field balance of the accelerating mode in the 1 ½ cell gun cavity is one of the key beam dynamics issues of the rf gun. Since no direct field measurement in the half and full cell of the cavity is available for the PITZ gun, a beam-based technique to determine the field balance has been proposed. A beam-based rf phase monitoring procedure has been developed as well.
Optimization Design of the Longitudinal Beam Based on Finite Analysis%基于有限元分析的乘用车前纵梁安全设计
Institute of Scientific and Technical Information of China (English)
张建; 柳东威; 张子鹏
2012-01-01
To enhance the security of vehicle crash, the longitudinal beam was optimized in this paper. The induction holes number, materials and thickness were taken as the factors. The vehicle collision test and sled test were simulated in LS-DYNA, according to the orthogonal table. The HIC value was taken as the injuries evaluation criteria. Through the poor analysis, the optimal longitudinal beam parameters were identified, and the occupant safety was improved.%为提升车辆撞击事故乘员的安全性,从诱导孔个数、前纵梁材料和梁壁厚三个方面对汽车前纵梁进行了优化设计。将上述三个方面作为影响因素进行了正交试验设计,按照正交表在LS-DYNA当中进行了整车碰撞及台车试验,以头部损伤HIC值作为乘员损伤评价标准,通过极差分析确定了最优汽车前纵梁参数,提高了汽车碰撞中乘员的安全。
Jia, Xun; Men, Chunhua; Lou, Yifei; Jiang, Steve B.
2011-10-01
Beam orientation optimization (BOO) is a key component in the process of intensity modulated radiation therapy treatment planning. It determines to what degree one can achieve a good treatment plan in the subsequent plan optimization process. In this paper, we have developed a BOO algorithm via adaptive l2, 1-minimization. Specifically, we introduce a sparsity objective function term into our model which contains weighting factors for each beam angle adaptively adjusted during the optimization process. Such an objective function favors a small number of beam angles. By optimizing a total objective function consisting of a dosimetric term and the sparsity term, we are able to identify unimportant beam angles and gradually remove them without largely sacrificing the dosimetric objective. In one typical prostate case, the convergence property of our algorithm, as well as how beam angles are selected during the optimization process, is demonstrated. Fluence map optimization (FMO) is then performed based on the optimized beam angles. The resulting plan quality is presented and is found to be better than that of equiangular beam orientations. We have further systematically validated our algorithm in the contexts of 5-9 coplanar beams for five prostate cases and one head and neck case. For each case, the final FMO objective function value is used to compare the optimized beam orientations with the equiangular ones. It is found that, in the majority of cases tested, our BOO algorithm leads to beam configurations which attain lower FMO objective function values than those of corresponding equiangular cases, indicating the effectiveness of our BOO algorithm. Superior plan qualities are also demonstrated by comparing DVH curves between BOO plans and equiangular plans.
GÖKDAĞ, Hakan
2013-01-01
In this work a crack identification method for beam type structures under moving vehicle is proposed. The basic of the method is to formulate damage detection as an inverse problem, and solve for damage locations and extents. To this end, an objective function is defined based on the difference of damaged beam dynamic response and the response calculated by the mathematical model of the beam. The optimization problem is solved through a popular evolutionary algorithm, i.e. the particle swarm ...
Optimization of atomic beam sources for polarization experiments
Energy Technology Data Exchange (ETDEWEB)
Gaisser, Martin; Nass, Alexander; Stroeher, Hans [IKP, Forschungszentrum Juelich (Germany)
2012-07-01
For experiments with spinpolarized protons and neutrons a dense target is required. In current atomic beam sources an atomic hydrogen or deuterium beam is expanded through a cold nozzle and a system of sextupole magnets and RF-transition units selects a certain hyperfine state. The achievable flux seems to be limited to about 10{sup 17} particles per second with a high nuclear polarization. A lot of experimental and theoretical effort has been undertaken to understand all effects and to increase the flux. However, improvements have remained marginal. Now, a Monte Carlo simulation based on the DSMC part of the open source C++ library OpenFOAM is set up in order to get a better understanding of the flow and to optimize the various elements. The goal is to include important effects like deflection from a magnetic field, recombination on the walls and spin exchange collisions in the simulation and make quantitative predictions of changes in the experimental setup. The goal is to get a tool that helps to further increase the output of an atomic beam source.
Optimization of atomic beam sources for polarization experiments
International Nuclear Information System (INIS)
For experiments with spinpolarized protons and neutrons a dense target is required. In current atomic beam sources an atomic hydrogen or deuterium beam is expanded through a cold nozzle and a system of sextupole magnets and RF-transition units selects a certain hyperfine state. The achievable flux seems to be limited to about 1017 particles per second with a high nuclear polarization. A lot of experimental and theoretical effort has been undertaken to understand all effects and to increase the flux. However, improvements have remained marginal. Now, a Monte Carlo simulation based on the DSMC part of the open source C++ library OpenFOAM is set up in order to get a better understanding of the flow and to optimize the various elements. The goal is to include important effects like deflection from a magnetic field, recombination on the walls and spin exchange collisions in the simulation and make quantitative predictions of changes in the experimental setup. The goal is to get a tool that helps to further increase the output of an atomic beam source.
Optimization of Circular Side Door Beam for Crashworthiness Analysis
Directory of Open Access Journals (Sweden)
Raja Sharmi Raja Husin
2012-01-01
Full Text Available Structural optimization related to crashworthiness and energy absorption capability is particularly importance to the automotive industry. The optimization involves highly nonlinear computational analysis and design with many material and structure parameters. This paper presents a crashworthiness design of the circular side door beam which attach to the side door structures. The response surface method (RSM is utilized to formulate the complex crashworthiness design problem in the case of optimization. In this study, side door beam will be optimized. The beams in circular shape were studied and compared. The focus is on finding an optimum cross-section shape of the beam in order to improve the energy absorption character. An optimization problem is formulated to find the maximum energy absorbed with the maximum peak load as a constraint, the shape of the beam cross section and the thickness as variable. The structure optimum design and simulation analysis of automobile side-door beam was carried out by using Finite Element (FE method.
IRT-Sofia BNCT beam tube optimization study
International Nuclear Information System (INIS)
An optimization study of IRT-Sofia BNCT beam tube is presented. In the study we used the MIT/FCB experience. The enlarging of filter/moderator cross section dimensions and the decreasing of collimator length within the limits of the IRT-Sofia reactor design were analyzed. The influence of beam and reactor core axes non-coincidence on the beam properties was also evaluated. The irradiation resistance of polytetrafluoroethylene (Teflon®) was also evaluated. The results provide information for making decisions on the IRT-Sofia BNCT beam construction.
IRT-Sofia BNCT beam tube optimization study
Energy Technology Data Exchange (ETDEWEB)
Belousov, S., E-mail: belousov@inrne.bas.bg [Institute for Nuclear Research and Nuclear Energy (INRNE) of the Bulgarian Academy of Sciences, Tsarigradsko 72, Sofia (Bulgaria); Mitev, M.; Ilieva, K. [Institute for Nuclear Research and Nuclear Energy (INRNE) of the Bulgarian Academy of Sciences, Tsarigradsko 72, Sofia (Bulgaria); Riley, K. [Radiation Monitoring Devices, Watertown, MA (United States); Harling, O. [Nuclear Science and Engineering Department, Massachusetts Institute of Technology, Cambridge, MA (United States)
2011-12-15
An optimization study of IRT-Sofia BNCT beam tube is presented. In the study we used the MIT/FCB experience. The enlarging of filter/moderator cross section dimensions and the decreasing of collimator length within the limits of the IRT-Sofia reactor design were analyzed. The influence of beam and reactor core axes non-coincidence on the beam properties was also evaluated. The irradiation resistance of polytetrafluoroethylene (Teflon{sup Registered-Sign }) was also evaluated. The results provide information for making decisions on the IRT-Sofia BNCT beam construction.
Institute of Scientific and Technical Information of China (English)
王强; 赵海龙; 代志勇; 孙文遂; 谢龙; 王文斗
2013-01-01
The beam transport system of the Dragon-I linear induction accelerator(LIA) consists of hundreds of solenoid coils and dipole steering coils, which are designed to reduce corkscrew amplitude and transverse motion of electron beam. In order to improve the beam quality, a genetic optimization model of solenoid currents is proposed in this paper and the optimization code GABC based on genetic algorithm and beam transport models is designed, which contains both beam centroid track and the beam envelope model. The matched magnetic field in five blocks of the Dragon- I LIA, including twenty induction acceleration cells and five connection cells, are analyzed using the optimization code. The numerical results reveal that the GABC is effective to solve transport magnetic field optimization problems and could play an important role for beam tuning simulation and experiment.%以直线感应加速器(LIA)匹配磁场设计和束线调谐为背景,提出解决强流相对论电子束长距离、小波动、多元件磁约束的输运优化问题的数值优化办法,建立基于遗传算法的优化程序.结合束质心轨迹及束包络耦合模型,设计描述束传输半径波动大小的评价函数,采用励磁元件馈入电流为优化对象,解决LIA磁场配置“组合爆炸”优化问题.计算结果表明:优化程序可依据不同的初始束流,有针对性地快速给出一组符合束输运要求的励磁电流配置.研究成果为在建的LIA装置束线调谐提供一种重要的数值分析工具.
SU-E-T-258: Parallel Optimization of Beam Configurations for CyberKnife Treatments
Energy Technology Data Exchange (ETDEWEB)
Viulet, T [Universitaet zu Luebeck, Luebeck (Germany); Blanck, O [CyberKnife Zentrum Norddeutschland, Guestrow (Germany); Schlaefer, A [Universitaet zu Luebeck, Luebeck (Germany); Hamburg University of Technology, Hamburg (Germany)
2014-06-01
Purpose: The CyberKnife delivers a large number of beams originating at different non-planar positions and with different orientation. We study how much the quality of treatment plans depends on the beams considered during plan optimization. Particularly, we evaluate a new approach to search for optimal treatment plans in parallel by running optimization steps concurrently. Methods: So far, no deterministic, complete and efficient method to select the optimal beam configuration for robotic SRS/SBRT is known. Considering a large candidate beam set increases the likelihood to achieve a good plan, but the optimization problem becomes large and impractical to solve. We have implemented an approach that parallelizes the search by solving multiple linear programming problems concurrently while iteratively resampling zero weighted beams. Each optimization problem contains the same set of constraints but different variables representing candidate beams. The search is synchronized by sharing the resulting basis variables among the parallel optimizations. We demonstrate the utility of the approach based on an actual spinal case with the objective to improve the coverage. Results: The objective function is falling and reaches a value of 5000 after 49, 31, 25 and 15 iterations for 1, 2, 4, and 8 parallel processes. This corresponds to approximately 97% coverage in 77%, 59%, and 36% of the mean number of iterations with one process for 2, 4, and 8 parallel processes, respectively. Overall, coverage increases from approximately 91.5% to approximately 98.5%. Conclusion: While on our current computer with uniform memory access the reduced number of iterations does not translate into a similar speedup, the approach illustrates how to effectively parallelize the search for the optimal beam configuration. The experimental results also indicate that for complex geometries the beam selection is critical for further plan optimization.
SU-E-T-258: Parallel Optimization of Beam Configurations for CyberKnife Treatments
International Nuclear Information System (INIS)
Purpose: The CyberKnife delivers a large number of beams originating at different non-planar positions and with different orientation. We study how much the quality of treatment plans depends on the beams considered during plan optimization. Particularly, we evaluate a new approach to search for optimal treatment plans in parallel by running optimization steps concurrently. Methods: So far, no deterministic, complete and efficient method to select the optimal beam configuration for robotic SRS/SBRT is known. Considering a large candidate beam set increases the likelihood to achieve a good plan, but the optimization problem becomes large and impractical to solve. We have implemented an approach that parallelizes the search by solving multiple linear programming problems concurrently while iteratively resampling zero weighted beams. Each optimization problem contains the same set of constraints but different variables representing candidate beams. The search is synchronized by sharing the resulting basis variables among the parallel optimizations. We demonstrate the utility of the approach based on an actual spinal case with the objective to improve the coverage. Results: The objective function is falling and reaches a value of 5000 after 49, 31, 25 and 15 iterations for 1, 2, 4, and 8 parallel processes. This corresponds to approximately 97% coverage in 77%, 59%, and 36% of the mean number of iterations with one process for 2, 4, and 8 parallel processes, respectively. Overall, coverage increases from approximately 91.5% to approximately 98.5%. Conclusion: While on our current computer with uniform memory access the reduced number of iterations does not translate into a similar speedup, the approach illustrates how to effectively parallelize the search for the optimal beam configuration. The experimental results also indicate that for complex geometries the beam selection is critical for further plan optimization
Beam shaping for laser-based adaptive optics in astronomy
Béchet, Clémentine; Guesalaga, Andrés; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani
2014-01-01
The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics syst...
Optimization of neutrino beams for underground sites in Europe
Longhin, A
2012-01-01
We present an optimization procedure for neutrino beams which could be produced at CERN and aimed to a set of seven possible underground sites in Europe with distances ranging from 130 km to 2300 km. Studies on the feasibility of a next generation very massive neutrino observatory have been performed for these sites in the context of the first phase of the LAGUNA design study. We consider specific scenarios for the proton driver (a high power proton driver at 4.5 GeV for the shortest baseline and a 50 GeV machine for longer baselines) and the far detector (a Water Cherenkov for the shortest baseline and a LAr TPC for longer baselines). The flux simulation profits of a full GEANT4 simulation. The optimization has been performed before the recent results on nu_e appearance by reactor and accelerator experiments and hence it is based on the maximization of the sensitivity on theta13. Nevertheless the optimized fluxes have been widely used since their publication on the internet (2010). This work is therefore mai...
Multi-material topology optimization of laminated composite beams with eigenfrequency constraints
DEFF Research Database (Denmark)
Blasques, José Pedro Albergaria Amaral
2014-01-01
This paper describes a methodology for simultaneous topology and material optimization in optimal design of laminated composite beams with eigenfrequency constraints. The structural response is analyzed using beam finite elements. The beam sectional properties are evaluated using a finite element...
An optimized nanoparticle separator enabled by electron beam induced deposition
International Nuclear Information System (INIS)
Size-based separations technologies will inevitably benefit from advances in nanotechnology. Direct-write nanofabrication provides a useful mechanism for depositing/etching nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam-interaction region. Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub-50 nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular-sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects) and (2) preserved the fidelity of the spacing between nanopillars (which maximizes the size-based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing.
Online optimization of storage ring nonlinear beam dynamics
Huang, Xiaobiao
2015-01-01
We propose to optimize the nonlinear beam dynamics of existing and future storage rings with direct online optimization techniques. This approach may have crucial importance for the implementation of diffraction limited storage rings. In this paper considerations and algorithms for the online optimization approach are discussed. We have applied this approach to experimentally improve the dynamic aperture of the SPEAR3 storage ring with the robust conjugate direction search method and the particle swarm optimization method. The dynamic aperture was improved by more than 5 mm within a short period of time. Experimental setup and results are presented.
Online optimization of storage ring nonlinear beam dynamics
Huang, Xiaobiao; Safranek, James
2015-08-01
We propose to optimize the nonlinear beam dynamics of existing and future storage rings with direct online optimization techniques. This approach may have crucial importance for the implementation of diffraction limited storage rings. In this paper considerations and algorithms for the online optimization approach are discussed. We have applied this approach to experimentally improve the dynamic aperture of the SPEAR3 storage ring with the robust conjugate direction search method and the particle swarm optimization method. The dynamic aperture was improved by more than 5 mm within a short period of time. Experimental setup and results are presented.
Optimization of laser accelerated proton beams for possible applications
International Nuclear Information System (INIS)
Optimization of transported proton beams through a pulsed solenoid in the laser proton experiment LIGHT at GSI has been studied numerically. TraceWin, SRIM and ATIMA codes were employed for this study with an initial distribution generated by MATLAB program fitted to Phelix measured data. Two individual tools have been used to produce protons beam as a later beam source: an aperture located at the solenoid focal spot as energy selection tool; and a scattering foil at a suitable position in the beam path that smoothens the simulated radial energy imprint on the beam profile. The simulation results show that the proton energy spectrum is filtered by the aperture and the radial energy correlation is smoothened.
Beam Delivery Simulation - Recent Developments and Optimization
AUTHOR|(INSPIRE)INSPIRE-00232566; Boogert, Stewart Takashi; Garcia-Morales, H; Gibson, Stephen; Kwee-Hinzmann, Regina; Nevay, Laurence James; Deacon, Lawrence Charles
2015-01-01
Beam Delivery Simulation (BDSIM) is a particle tracking code that simulates the passage of particles through both the magnetic accelerator lattice as well as their interaction with the material of the accelerator itself. The Geant4 toolkit is used to give a full range of physics processes needed to simulate both the interaction of primary particles and the production and subsequent propagation of secondaries. BDSIM has already been used to simulate linear accelerators such as the International Linear Collider (ILC) and the Compact Linear Collider (CLIC), but it has recently been adapted to simulate circular accelerators as well, producing loss maps for the Large Hadron Collider (LHC). In this paper the most recent developments, which extend BDSIM’s functionality as well as improve its efficiency are presented. Improvement and refactorisation of the tracking algorithms are presented alongside improved automatic geometry construction for increased particle tracking speed.
Optimization of a constrained linear monochromator design for neutral atom beams.
Kaltenbacher, Thomas
2016-04-01
A focused ground state, neutral atom beam, exploiting its de Broglie wavelength by means of atom optics, is used for neutral atom microscopy imaging. Employing Fresnel zone plates as a lens for these beams is a well established microscopy technique. To date, even for favorable beam source conditions a minimal focus spot size of slightly below 1μm was reached. This limitation is essentially given by the intrinsic spectral purity of the beam in combination with the chromatic aberration of the diffraction based zone plate. Therefore, it is important to enhance the monochromaticity of the beam, enabling a higher spatial resolution, preferably below 100nm. We propose to increase the monochromaticity of a neutral atom beam by means of a so-called linear monochromator set-up - a Fresnel zone plate in combination with a pinhole aperture - in order to gain more than one order of magnitude in spatial resolution. This configuration is known in X-ray microscopy and has proven to be useful, but has not been applied to neutral atom beams. The main result of this work is optimal design parameters based on models for this linear monochromator set-up followed by a second zone plate for focusing. The optimization was performed for minimizing the focal spot size and maximizing the centre line intensity at the detector position for an atom beam simultaneously. The results presented in this work are for, but not limited to, a neutral helium atom beam. PMID:26922370
Peng, Jie; Zhu, Jianhua; Li, Tong
2016-06-01
The thermal lens effect of 2.1 μm Cr, Tm, Ho: YAG (CTH:YAG) solid-state laser under high pumping power condition is analyzed, and a symmetric spherical resonator which is insensitive to thermal focal length change is proposed to improve the beam quality of Fabry-Perot (F-P) resonator. Then the gradient-reflectivity mirror is introduced as output mirror to optimize the resonator mode and beam quality. Based on the scalar diffraction theory, the Fox-Li numerical iteration method and fast Fourier transform (FFT) algorithm are used to calculate the resonator mode and output power distribution of resonators with Gaussian, super-Gaussian and parabolic gradient mirror, respectively. By comparing the cavity loss and beam quality, one can find that the symmetric spherical resonator with a super-Gaussian mirror can provide the best output beam quality, it has the minimum cavity loss of 0.1907, the minimum far-field divergence angle of 1 mrad and the maximum power in the bucket (PIB) of 89.42%.
Optimizing Stellarators for Energetic Particle Confinement using BEAMS3D
Bolgert, Peter; Drevlak, Michael; Lazerson, Sam; Gates, David; White, Roscoe
2015-11-01
Energetic particle (EP) loss has been called the ``Achilles heel of stellarators,'' (Helander, Rep. Prog. Phys. 77 087001 (2014)) and there is a great need for magnetic configurations with improved EP confinement. In this study we utilize a newly developed capability of the stellarator optimization code STELLOPT: the ability to optimize EP confinement via an interface with guiding center code BEAMS3D (McMillan et al., Plasma Phys. Control. Fusion 56, 095019 (2014)). Using this new tool, optimizations of the W7-X experiment and ARIES-CS reactor are performed where the EP loss fraction is one of many target functions to be minimized. In W7-X, we simulate the experimental NBI system using realistic beam geometry and beam deposition physics. The goal is to find configurations with improved neutral beam deposition and energetic particle confinement. These calculations are compared to previous studies of W7-X NBI deposition. In ARIES-CS, we launch 3.5 MeV alpha particles from a near-axis flux surface using a uniform grid in toroidal and poloidal angle. As these particles are born from D-T reactions, we consider an isotropic distribution in velocity space. This research is supported by DoE Contract Number DE-AC02-09CH11466.
Optimized optical "tractor beam" for core-shell nanoparticles.
Wang, Neng; Lu, Wanli; Ng, Jack; Lin, Zhifang
2014-04-15
It is known that core-shell subwavelength nanoparticles consisting of a dielectric shell and a metallic core can simultaneously support electric and magnetic dipolar resonances, which enhance forward scattering and suppress backward scattering. This creates favorable conditions for optical tractor beam applications. Using the generalized Lorenz-Mie theory and Maxwell stress tensor formulation, we demonstrate how optical pulling forces can be induced and optimized by first-order Bessel beams with appropriate polarization. The transverse stability of the core-shell nanoparticle under ambient damping is also verified by linear stability analysis and dynamical simulation. PMID:24979003
Optimal centralized and decentralized velocity feedback control on a beam
International Nuclear Information System (INIS)
This paper considers the optimization of a velocity feedback controller with a collocated force actuator, to minimize the kinetic energy of a simply supported beam. If the beam is excited at a single location, the optimum feedback gain varies with the position of the control system. It is shown that this variation depends partly on the location of the control force relative to the exciting force. If a distributed excitation is assumed, that is random in both time and space, a unique optimum value of the feedback gain can be found for a given control location. The effect of the control location on performance and the optimal feedback gain can then be examined and is found to be limited provided the control locations are not close to the ends of the beam. The optimization can also be performed for a multichannel velocity feedback system. Both a centralized and a decentralized controller are considered. It is shown that the difference in performance between a centralized and a decentralized controller is small, unless the control locations are closely spaced. In this case the centralized controller effectively feeds back a moment proportional to angular velocity as well as a force proportional to a velocity. It is also shown that the optimal feedback gain can be approximated on the basis of a limited model and that similar results can be achieved
Thermo-mechanical simulation and parameters optimization for beam blank continuous casting
International Nuclear Information System (INIS)
The objective of this work is to optimize the process parameters of beam blank continuous casting in order to ensure high quality and productivity. A transient thermo-mechanical finite element model is developed to compute the temperature and stress profile in beam blank continuous casting. By comparing the calculated data with the metallurgical constraints, the key factors causing defects of beam blank can be found out. Then based on the subproblem approximation method, an optimization program is developed to search out the optimum cooling parameters. Those optimum parameters can make it possible to run the caster at its maximum productivity, minimum cost and to reduce the defects. Now, online verifying of this optimization project has been put in practice, which can prove that it is very useful to control the actual production
How beam driven operations optimize ALICE efficiency and safety
International Nuclear Information System (INIS)
ALICE is one of the experiments at the Large Hadron Collider (LHC), CERN (Geneva, Switzerland). The ALICE DCS is responsible for the coordination and monitoring of the various detectors and of central systems, for collecting and managing alarms, data and commands. Furthermore, it's the central tool to monitor and verify the beam status with special emphasis on safety. In particular, it is important to ensure that the experiment's detectors are brought to and stay in a safe state, e.g. reduced voltages during the injection, acceleration, and adjusting phases of the LHC beams. Thanks to its central role, it's the appropriate system to implement automatic actions that were normally left to the initiative of the shift leader; where decisions come from the knowledge of detectors’ statuses and of the beam, combined together to fulfil the scientific requirements, keeping safety as a priority in all cases. This paper shows how the central DCS is interpreting the daily operations from a beam driven point of view. A tool is being implemented where automatic actions can be set and monitored through expert panels, with a custom level of automatization. Some routine operations are already automated, when a particular beam mode is declared by the LHC, which can represent a safety concern. This beam driven approach is proving to be a tool for the shift crew to optimize the efficiency of data taking, while improving the safety of the experiment.
Automatic learning-based beam angle selection for thoracic IMRT
Energy Technology Data Exchange (ETDEWEB)
Amit, Guy; Marshall, Andrea [Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario M5G 2M9 (Canada); Purdie, Thomas G., E-mail: tom.purdie@rmp.uhn.ca; Jaffray, David A. [Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario M5G 2M9 (Canada); Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Techna Institute, University Health Network, Toronto, Ontario M5G 1P5 (Canada); Levinshtein, Alex [Department of Computer Science, University of Toronto, Toronto, Ontario M5S 3G4 (Canada); Hope, Andrew J.; Lindsay, Patricia [Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, Ontario M5G 2M9, Canada and Department of Radiation Oncology, University of Toronto, Toronto, Ontario M5S 3E2 (Canada); Pekar, Vladimir [Philips Healthcare, Markham, Ontario L6C 2S3 (Canada)
2015-04-15
Purpose: The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process, which requires the planner to iterate between choosing beam angles, specifying dose–volume objectives and executing IMRT optimization. In thorax treatment planning, where there are no class solutions for beam placement, beam angle selection is performed manually, based on the planner’s clinical experience. The purpose of this work is to propose and study a computationally efficient framework that utilizes machine learning to automatically select treatment beam angles. Such a framework may be helpful for reducing the overall planning workload. Methods: The authors introduce an automated beam selection method, based on learning the relationships between beam angles and anatomical features. Using a large set of clinically approved IMRT plans, a random forest regression algorithm is trained to map a multitude of anatomical features into an individual beam score. An optimization scheme is then built to select and adjust the beam angles, considering the learned interbeam dependencies. The validity and quality of the automatically selected beams evaluated using the manually selected beams from the corresponding clinical plans as the ground truth. Results: The analysis included 149 clinically approved thoracic IMRT plans. For a randomly selected test subset of 27 plans, IMRT plans were generated using automatically selected beams and compared to the clinical plans. The comparison of the predicted and the clinical beam angles demonstrated a good average correspondence between the two (angular distance 16.8° ± 10°, correlation 0.75 ± 0.2). The dose distributions of the semiautomatic and clinical plans were equivalent in terms of primary target volume
Automatic learning-based beam angle selection for thoracic IMRT
International Nuclear Information System (INIS)
Purpose: The treatment of thoracic cancer using external beam radiation requires an optimal selection of the radiation beam directions to ensure effective coverage of the target volume and to avoid unnecessary treatment of normal healthy tissues. Intensity modulated radiation therapy (IMRT) planning is a lengthy process, which requires the planner to iterate between choosing beam angles, specifying dose–volume objectives and executing IMRT optimization. In thorax treatment planning, where there are no class solutions for beam placement, beam angle selection is performed manually, based on the planner’s clinical experience. The purpose of this work is to propose and study a computationally efficient framework that utilizes machine learning to automatically select treatment beam angles. Such a framework may be helpful for reducing the overall planning workload. Methods: The authors introduce an automated beam selection method, based on learning the relationships between beam angles and anatomical features. Using a large set of clinically approved IMRT plans, a random forest regression algorithm is trained to map a multitude of anatomical features into an individual beam score. An optimization scheme is then built to select and adjust the beam angles, considering the learned interbeam dependencies. The validity and quality of the automatically selected beams evaluated using the manually selected beams from the corresponding clinical plans as the ground truth. Results: The analysis included 149 clinically approved thoracic IMRT plans. For a randomly selected test subset of 27 plans, IMRT plans were generated using automatically selected beams and compared to the clinical plans. The comparison of the predicted and the clinical beam angles demonstrated a good average correspondence between the two (angular distance 16.8° ± 10°, correlation 0.75 ± 0.2). The dose distributions of the semiautomatic and clinical plans were equivalent in terms of primary target volume
Ultra-fast fluence optimization for beam angle selection algorithms
Bangert, M.; Ziegenhein, P.; Oelfke, U.
2014-03-01
Beam angle selection (BAS) including fluence optimization (FO) is among the most extensive computational tasks in radiotherapy. Precomputed dose influence data (DID) of all considered beam orientations (up to 100 GB for complex cases) has to be handled in the main memory and repeated FOs are required for different beam ensembles. In this paper, the authors describe concepts accelerating FO for BAS algorithms using off-the-shelf multiprocessor workstations. The FO runtime is not dominated by the arithmetic load of the CPUs but by the transportation of DID from the RAM to the CPUs. On multiprocessor workstations, however, the speed of data transportation from the main memory to the CPUs is non-uniform across the RAM; every CPU has a dedicated memory location (node) with minimum access time. We apply a thread node binding strategy to ensure that CPUs only access DID from their preferred node. Ideal load balancing for arbitrary beam ensembles is guaranteed by distributing the DID of every candidate beam equally to all nodes. Furthermore we use a custom sorting scheme of the DID to minimize the overall data transportation. The framework is implemented on an AMD Opteron workstation. One FO iteration comprising dose, objective function, and gradient calculation takes between 0.010 s (9 beams, skull, 0.23 GB DID) and 0.070 s (9 beams, abdomen, 1.50 GB DID). Our overall FO time is < 1 s for small cases, larger cases take ~ 4 s. BAS runs including FOs for 1000 different beam ensembles take ~ 15-70 min, depending on the treatment site. This enables an efficient clinical evaluation of different BAS algorithms.
DPSS Laser Beam Quality Optimization Through Pump Current Tuning
Energy Technology Data Exchange (ETDEWEB)
Omohundro, Rob; /Newport Spectra-Physics, Santa Clara; Callen, Alice; /SLAC; Sukuta, Sydney; /San Jose City Coll.
2012-03-30
The goal of this study is to demonstrate how a DPSS laser beam's quality parameters can be simultaneously optimized through pump current tuning. Two DPSS lasers of the same make and model were used where the laser diode pump current was first varied to ascertain the lowest RMS noise region. The lowest noise was found to be 0.13% in this region and the best M{sup 2} value of 1.0 and highest laser output power were simultaneously attained at the same current point. The laser manufacturer reported a M{sup 2} value of 1.3 and RMS noise value of .14% for these lasers. This study therefore demonstrates that pump current tuning a DPSS laser can simultaneously optimize RMS Noise, Power and M{sup 2} values. Future studies will strive to broaden the scope of the beam quality parameters impacted by current tuning.
Risk Based Optimal Fatigue Testing
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Faber, M.H.; Kroon, I.B.
1992-01-01
Optimal fatigue life testing of materials is considered. Based on minimization of the total expected costs of a mechanical component a strategy is suggested to determine the optimal stress range levels for which additional experiments are to be performed together with an optimal value of the maxi......Optimal fatigue life testing of materials is considered. Based on minimization of the total expected costs of a mechanical component a strategy is suggested to determine the optimal stress range levels for which additional experiments are to be performed together with an optimal value...... of the maximum number of load cycles performed before experiment termination. The approach utilizes to a large extent standard statistical and decision theoretical tools and is formulated such that the necessary calculations are easily performed using nested FORM/SORM. The suggested approach is illustrated...
Constrained Response Surface Optimization for a Laser Beam Welding Process
Directory of Open Access Journals (Sweden)
Pongchanun Luangpaiboon
2011-01-01
Full Text Available Problem statement: On a current operating condition of a laser beam welding process in the hard disk drive industry, it has been found that shear strength of the head support and suspension assembly is slightly higher than customers' specification. This situation leads to an inspection with a large sample size and a high frequency. Shear strength is not only one quality characteristic for this assembly, but other critical physical specifications of welding diameter and depth need to be also considered. Approach: A hybridization strategy, based on linear and nonlinear Constrained Response Surface Optimization Methods (CRSOM, has been developed for this process refinement. The hybridization is having a provision to include both explicit constraints of influential process variables as well as implicit constraints of physical specifications. Results: The proposed levels of influential process variables have been successfully implemented in terms of shear strength and satisfied both welding diameter and depth specifications. Conclusion: The advantage of the hybridization compared with individually CRSOM is that all the data from the experiment is collected together to make a final decision. When engineering problems are large and complicated, an effective finite sequence of instructions from the hybridization can be very useful and practical in setting industrial processes such as semiconductor or automotive manufacturing systems.
Optimization of Laminated Composite Z-Section Beam
Directory of Open Access Journals (Sweden)
Sanjay Gupta
2014-02-01
Full Text Available The abstract should summarize the content of the paper. Composites are the relatively new but fast growing field where the researchers are paying their lots of attention. Ever growing market needs always better material and product which is lighter in weight but more strengthen in nature. To justify the current needs this project pays some attention to increase the performance of the composite product by means of some modern optimization techniques. The benefit of material properties and flexibility of selecting material have made composite materials a key preference for structural application. Dissimilar to isotropic materials, the parametric study of laminated composite beams for optimized design is complex due to more number of parameters concerned in designing like lay-up sequence, and layer configuration. Furthermore, the restrictions of FEA methods in designing have created a requirement for an optimum solution for analysis of laminated composite beams structure. The goal of this study focuses on the optimization of composite Z-beam for lowest deflection by a static analysis. Composite materials are extensively being used in aircraft, robotic and automotive industries where the parts are subjected to various loading situations. There is a requirement for the precise prediction of for their static response uniqueness so that they can be designed against the failure because of different types of possible static loads. Here the parameterization of composite is done and then through various parameters like number of ply, ply thickness and ply location etc. the optimization has been done to reduce the weight and other performance criteria‟s for Z-beam (thin walled composite plate.
Directory of Open Access Journals (Sweden)
Heng Wang
2014-01-01
Full Text Available Multi-spot-beam technique has been widely applied in modern satellite communication systems. However, the satellite power and bandwidth resources in a multi-spot-beam satellite communication system are scarce and expensive; it is urgent to utilize the resources efficiently. To this end, dynamically allocating the power and bandwidth is an available way. This paper initially formulates the problem of resource joint allocation as a convex optimization problem, taking into account a compromise between the maximum total system capacity and the fairness among the spot beams. A joint bandwidth and power allocation iterative algorithm based on duality theory is then proposed to obtain the optimal solution of this optimization problem. Compared with the existing separate bandwidth or power optimal allocation algorithms, it is shown that the joint allocation algorithm improves both the total system capacity and the fairness among spot beams. Moreover, it is easy to be implemented in practice, as the computational complexity of the proposed algorithm is linear with the number of spot beams.
Simultaneous beam sampling and aperture shape optimization for SPORT
International Nuclear Information System (INIS)
Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and
Simultaneous beam sampling and aperture shape optimization for SPORT
Energy Technology Data Exchange (ETDEWEB)
Zarepisheh, Masoud; Li, Ruijiang; Xing, Lei, E-mail: Lei@stanford.edu [Department of Radiation Oncology, Stanford University, Stanford, California 94305 (United States); Ye, Yinyu [Department of Management Science and Engineering, Stanford University, Stanford, California 94305 (United States)
2015-02-15
Purpose: Station parameter optimized radiation therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital linear accelerators, in which the station parameters of a delivery system, such as aperture shape and weight, couch position/angle, gantry/collimator angle, can be optimized simultaneously. SPORT promises to deliver remarkable radiation dose distributions in an efficient manner, yet there exists no optimization algorithm for its implementation. The purpose of this work is to develop an algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: The authors build a mathematical model with the fundamental station point parameters as the decision variables. To solve the resulting large-scale optimization problem, the authors devise an effective algorithm by integrating three advanced optimization techniques: column generation, subgradient method, and pattern search. Column generation adds the most beneficial stations sequentially until the plan quality improvement saturates and provides a good starting point for the subsequent optimization. It also adds the new stations during the algorithm if beneficial. For each update resulted from column generation, the subgradient method improves the selected stations locally by reshaping the apertures and updating the beam angles toward a descent subgradient direction. The algorithm continues to improve the selected stations locally and globally by a pattern search algorithm to explore the part of search space not reachable by the subgradient method. By combining these three techniques together, all plausible combinations of station parameters are searched efficiently to yield the optimal solution. Results: A SPORT optimization framework with seamlessly integration of three complementary algorithms, column generation, subgradient method, and pattern search, was established. The proposed technique was applied to two previously treated clinical cases: a head and
Perera Velamazán, Ricardo; Sevillano Bravo, Enrique; Diego Villalón, Ana de; Arteaga Iriarte, Ángel
2014-01-01
Fiber reinforced polymer composites (FRP) have found widespread usage in the repair and strengthening of concrete structures. FRP composites exhibit high strength-to-weight ratio, corrosion resistance, and are convenient to use in repair applications. Externally bonded FRP flexural strengthening of concrete beams is the most extended application of this technique. A common cause of failure in such members is associated with intermediate crack-induced debonding (IC debonding) of the FRP substr...
International Nuclear Information System (INIS)
larger number of beams (e.g., seven). This two-step process is considerably faster than full exhaustive search. The question to be answered was whether the two methods lead to the same or similar solutions. The results of exhaustive search and multiresolution approaches were also compared with a previously published approach that used beam's-eye-view dosimetrics (BEVD). Results: The relative ranks of plans optimized by an accurate dose calculation method were highly correlated with those of the plans optimized by the fast calculation method (i.e., using the IV approximation), which suggests that an approximate dose calculation algorithm can be used effectively for ranking of plans during BAO. We found that dose distributions and DVH of many beam configurations within a specified subset from a given pool of beams (e.g., 5 of 18) may be clinically indistinguishable and acceptable. Their optimized IMRT scores fall in a narrow range, although beam configurations and dose distributions may be different. We used the frequency distributions as a function of beam angles for the best 100 and the worst 100 plans to determine the most and the least preferred beam angles. We found that the most and the least preferred angle distributions for 3 of 18 configurations were very similar to those for 5, 6, 7, or 8 of 18 or 24 configurations, but the size of the search space was much smaller for the 3 of 18 case. Using fewer than three beams was discovered to be inadequate. This information was used to select the most preferred angles and eliminate the least preferred ones before searching for the optimum angles for the remaining beams. For the cases we studies, the multiresolution strategy produced very similar results to the full exhaustive search. Based on the observation that the worst plans had at least one parallel-opposed pair of beams and virtually all of the best plans had none, we were able to further reduce the size of the search space dramatically by using a pool of only
Energy Technology Data Exchange (ETDEWEB)
Breedveld, Sebastiaan; Storchi, Pascal R. M.; Voet, Peter W. J.; Heijmen, Ben J. M. [Department of Radiation Oncology, Erasmus MC Rotterdam, Groene Hilledijk 301, 3075 EA Rotterdam (Netherlands)
2012-02-15
Purpose: To introduce iCycle, a novel algorithm for integrated, multicriterial optimization of beam angles, and intensity modulated radiotherapy (IMRT) profiles. Methods: A multicriterial plan optimization with iCycle is based on a prescription called wish-list, containing hard constraints and objectives with ascribed priorities. Priorities are ordinal parameters used for relative importance ranking of the objectives. The higher an objective priority is, the higher the probability that the corresponding objective will be met. Beam directions are selected from an input set of candidate directions. Input sets can be restricted, e.g., to allow only generation of coplanar plans, or to avoid collisions between patient/couch and the gantry in a noncoplanar setup. Obtaining clinically feasible calculation times was an important design criterium for development of iCycle. This could be realized by sequentially adding beams to the treatment plan in an iterative procedure. Each iteration loop starts with selection of the optimal direction to be added. Then, a Pareto-optimal IMRT plan is generated for the (fixed) beam setup that includes all so far selected directions, using a previously published algorithm for multicriterial optimization of fluence profiles for a fixed beam arrangement Breedveld et al.[Phys. Med. Biol. 54, 7199-7209 (2009)]. To select the next direction, each not yet selected candidate direction is temporarily added to the plan and an optimization problem, derived from the Lagrangian obtained from the just performed optimization for establishing the Pareto-optimal plan, is solved. For each patient, a single one-beam, two-beam, three-beam, etc. Pareto-optimal plan is generated until addition of beams does no longer result in significant plan quality improvement. Plan generation with iCycle is fully automated. Results: Performance and characteristics of iCycle are demonstrated by generating plans for a maxillary sinus case, a cervical cancer patient, and a
The SPL-based Neutrino Super Beam
Baussan, E; Bobeth, C; Bouquerel, E; Caretta, O; Cupial, P; Davenne, T; Densham, C; Dracos, M; Fitton, M; Gaudiot, G; Kozien, M; Lacny, L; Lepers, B; Longhin, A; Loveridge, P; Osswald, F; Poussot, P; Rooney, M; Skoczen, B; Szybinski, B; Ustrzycka, A; Vassilopoulos, N; Wilcox, D; Wroblewski, A; Wurtz, J; Zeter, V; Zito, M
2012-01-01
The EUROnu Super Beam work package has studied a neutrino beam based on SPL at CERN and aimed at MEMPHYS, a large water Cherenkov detector, proposed for the Laboratoire Souterrain de Modane (Fr\\'ejus tunnel, France), with a baseline of 130 km. The aim of this proposed experiment is to study the CP violation in the neutrino sector. In the study reported here, we have developed the conceptual design of the neutrino beam, especially the target and the magnetic focusing device. Indeed, this beam present several unprecedented challenges, like the high primary proton beam power (4 MW), the high repetition rate (50 Hz) and the low energy of the protons (4.5 GeV). The design is completed by a study of all the main component of the system, starting from the transport system to guide the beam to the target up to the beam dump.
International Nuclear Information System (INIS)
This study concerns new investigation of active vibration reduction of a stiffened plate bonded with discrete sensor/actuator pairs located optimally using genetic algorithms based on a developed finite element modeling. An isotropic plate element stiffened by a number of beam elements on its edges and having a piezoelectric sensor and actuator pair bonded to its surfaces is modeled using the finite element method and Hamilton’s principle, taking into account the effects of piezoelectric mass, stiffness and electromechanical coupling. The modeling is based on the first order shear deformation theory taking into account the effects of bending, membrane and shear deformation for the plate, the stiffening beam and the piezoelectric patches. A Matlab finite element program has been built for the stiffened plate model and verified with ANSYS and also experimentally. Optimal placement of ten piezoelectric sensor/actuator pairs and optimal feedback gain for active vibration reduction are investigated for a plate stiffened by two beams arranged in the form of a cross. The genetic algorithm was set up for optimization of sensor/actuator placement and feedback gain based on the minimization of the optimal linear quadratic index as an objective function to suppress the first six modes of vibration. Comparison study is presented for active vibration reduction of a square cantilever plate stiffened by crossed beams with two sensor/actuator configurations: firstly, ten piezoelectric sensor/actuator pairs are located in optimal positions; secondly, a piezoelectric layer of single sensor/actuator pair covering the whole of the stiffened plate as a SISO system. (paper)
Thermal analysis and optimization of proton beam window for the CSNS
International Nuclear Information System (INIS)
The proton beam window (PBW) is one of the key devices of China Spallation Neutron Source (CSNS). It is the boundary between transport line and target. This paper will present a new PBW structure and detailed thermal-stress analysis. The energy deposition and scattering effect need to be low when the beam passes through the PBW, so proper selection of material and structure is important. According to the study of energy deposition, A5083-O is selected as the PBW material. A single-double layer structure is first proposed based on the study of cooling structures. Thermal analysis and structural optimization are discussed, and transient analysis is done to show the effect of the beam pulse. Besides, safety is confirmed for cases of cooling tunnel blockage, beam profile shrinkage, or centroid orbit offset. All these analyses show the newly designed PBW structure can meet the requirements of the CSNS well. (authors)
Optimized Superconducting Quadrupole Arrays for Multiple Beam Transport
Energy Technology Data Exchange (ETDEWEB)
Meinke, Rainer, B.; Goodzeit, Carl, L.; Ball, Millicent, J.
2005-09-20
This research project advanced the development of reliable, cost-effective arrays of superconducting quadrupole magnets for use in multi-beam inertial fusion accelerators. The field in each array cell must be identical and meet stringent requirements for field quality and strength. An optimized compact array design using flat double-layer pancake coils was developed. Analytical studies of edge termination methods showed that it is feasible to meet the requirements for field uniformity in all cells and elimination of stray external field in several ways: active methods that involve placement of field compensating coils on the periphery of the array or a passive method that involves use of iron shielding.
Optimal collinear Gaussian beams for spontaneous parametric down-conversion
International Nuclear Information System (INIS)
I investigate the properties of spontaneous parametric down-conversion (SPDC) involving collinear Gaussian spatial modes for the pump and the photon collection optics. Approximate analytical and numerical results are obtained for the peak spectral density, photon bandwidth, pair collection probability, heralding ratio, and spectral purity as a function of crystal length and beam-focusing parameters. I address the optimization of these properties individually as well as jointly, and find focusing conditions that simultaneously bring the pair collection probability, heralding ratio, and spectral purity to near-optimal values. These properties are also found to be nearly scale invariant, that is, ultimately independent of crystal length. The results obtained here are expected to be useful for designing SPDC sources with high performance in multiple categories for the next generation of SPDC applications.
Optimization of Neutron Beam Techniques for Haracterization of Structural Materials
International Nuclear Information System (INIS)
The result of the activities on the CRP project titled: Optimization of Neutron Beam Techniques for Characterization of Structural Materials has been reported. The activities consist of individual project which was proposed at the beginning of the project and collaborative works which is jointly carried out with the other members of the CRP. The individual project which is mainly focused on the optimization of the neutron diffractometer and neutron radiography has been sucessfully completed. The collaborative works which are mainly targeted to perform Round Robin exercise using VAMAS sample for neutron diffractometer and standard samples for tomography obtained from PSI have been carried out sucessfully. However, the texture measurement on Al alloys, applying data correction was not sucessfully achieved since the proper standard sample is not available and this is still needed for the the future plan. (author)
Simulation based analysis of laser beam brazing
Dobler, Michael; Wiethop, Philipp; Schmid, Daniel; Schmidt, Michael
2016-03-01
Laser beam brazing is a well-established joining technology in car body manufacturing with main applications in the joining of divided tailgates and the joining of roof and side panels. A key advantage of laser brazed joints is the seam's visual quality which satisfies highest requirements. However, the laser beam brazing process is very complex and process dynamics are only partially understood. In order to gain deeper knowledge of the laser beam brazing process, to determine optimal process parameters and to test process variants, a transient three-dimensional simulation model of laser beam brazing is developed. This model takes into account energy input, heat transfer as well as fluid and wetting dynamics that lead to the formation of the brazing seam. A validation of the simulation model is performed by metallographic analysis and thermocouple measurements for different parameter sets of the brazing process. These results show that the multi-physical simulation model not only can be used to gain insight into the laser brazing process but also offers the possibility of process optimization in industrial applications. The model's capabilities in determining optimal process parameters are exemplarily shown for the laser power. Small deviations in the energy input can affect the brazing results significantly. Therefore, the simulation model is used to analyze the effect of the lateral laser beam position on the energy input and the resulting brazing seam.
Parametric Optimization of Nd:YAG Laser Beam Machining Process Using Artificial Bee Colony Algorithm
Directory of Open Access Journals (Sweden)
Rajarshi Mukherjee
2013-01-01
Full Text Available Nd:YAG laser beam machining (LBM process has a great potential to manufacture intricate shaped microproducts with its unique characteristics. In practical applications, such as drilling, grooving, cutting, or scribing, the optimal combination of Nd:YAG LBM process parameters needs to be sought out to provide the desired machining performance. Several mathematical techniques, like Taguchi method, desirability function, grey relational analysis, and genetic algorithm, have already been applied for parametric optimization of Nd:YAG LBM processes, but in most of the cases, suboptimal or near optimal solutions have been reached. This paper focuses on the application of artificial bee colony (ABC algorithm to determine the optimal Nd:YAG LBM process parameters while considering both single and multiobjective optimization of the responses. A comparative study with other population-based algorithms, like genetic algorithm, particle swarm optimization, and ant colony optimization algorithm, proves the global applicability and acceptability of ABC algorithm for parametric optimization. In this algorithm, exchange of information amongst the onlooker bees minimizes the search iteration for the global optimal and avoids generation of suboptimal solutions. The results of two sample paired t-tests also demonstrate its superiority over the other optimization algorithms.
Experimental optimization of beam quality extracted from a duoplasmatron proton ion source
Energy Technology Data Exchange (ETDEWEB)
Batygin, Y. K.; Draganic, I. N.; Fortgang, C. M. [LANL, Los Alamos, New Mexico 87545 (United States)
2014-10-01
The LANSCE accelerator facility operates with two independent ion injectors for H⁺ and H⁻ particle beams. The H⁺ ion beam is formed using a duoplasmatron source followed by a 750 keV Cockroft-Walton accelerating column. Formation of an optimal plasma meniscus is an important feature for minimizing beam emittance, and maximizing beam brightness. A series of experiments were performed to find the optimal combination of extraction voltage and extracted current for the H⁺ beam. Measurements yielded the best ratio of beam perveance to Child–Langmuir perveance of 0.52 for maximizing beam brightness.
Bunch Compressor for Beam-Based Alignment
Latina, A; Schulte, D
2007-01-01
Misalignments in the main linac of future linear colliders can lead to significant emittance growth. Beam-based alignment algorithms, such as Dispersion Free Steering (DFS), are necessary to mitigate these effects. We study how to use the Bunch Compressor to create the off-energy beams necessary for DFS and discuss the effectiveness of this method.
Optimal Location of TCSC Using Opposition Teaching Learning Based Optimization
Pranabesh Mukhopadhyay; Susanta Dutta; Provas Kumar Roy
2015-01-01
This paper focuses on the optimal power flow solution and the enhancement of the performance of a power system network. The paper presents a secured optimal power flow solution by integrating Thyristor controlled series compensator (TCSC) with the optimization model developed under overload condition. The Teaching Learning Based Optimization (TLBO) has been implemented here. Recently, the opposition-based learning (OBL) technique has been applied in various conventional population based techn...
Yarmand, Hamed
2013-01-01
Stereotactic body radiotherapy (SBRT) is characterized by delivering a high amount of dose in a short period of time. In SBRT the dose is delivered using open fields (e.g., beam's-eye-view) known as "apertures". Mathematical methods can be used for optimizing treatment planning for delivery of sufficient dose to the cancerous cells while keeping the dose to surrounding organs at risk (OARs) minimal. Two important elements of a treatment plan are quality and delivery time. Quality of a plan is measured based on the target coverage and dose to OARs. Delivery time heavily depends on the number of beams used in the plan since the setup times for different beam directions constitute a large portion of the delivery time. Therefore the ideal plan, in which all potential beams can be used simultaneously, will be associated with a long impractical delivery time. We use the dose to OARs in the ideal plan to find the plan with the minimum number of beams which is guaranteed to be epsilon-optimal (i.e., a predetermined m...
Simulation-based optimization parametric optimization techniques and reinforcement learning
Gosavi, Abhijit
2003-01-01
Simulation-Based Optimization: Parametric Optimization Techniques and Reinforcement Learning introduces the evolving area of simulation-based optimization. The book's objective is two-fold: (1) It examines the mathematical governing principles of simulation-based optimization, thereby providing the reader with the ability to model relevant real-life problems using these techniques. (2) It outlines the computational technology underlying these methods. Taken together these two aspects demonstrate that the mathematical and computational methods discussed in this book do work. Broadly speaking, the book has two parts: (1) parametric (static) optimization and (2) control (dynamic) optimization. Some of the book's special features are: *An accessible introduction to reinforcement learning and parametric-optimization techniques. *A step-by-step description of several algorithms of simulation-based optimization. *A clear and simple introduction to the methodology of neural networks. *A gentle introduction to converg...
Optimization of ripple filter for pencil beam scanning
International Nuclear Information System (INIS)
This paper presents a novel approach to seek the bar width for ripple filter used in pencil beam scanning proton therapy. A weight decay quadratic programming method is employed for the new optimization strategy. Compared to the commonly used iterative-least-square technique, the ripple filter derived by the proposed method not only has better depth dose uniformity, i.e., the dose uniformity is within 0.5%, but also has triangle-like vertical cross-sectional shape which is suitable for manufacture. Moreover, the new method has such good robust characteristics that it is also applicable to the real application with unavoidable measurement errors and noises. The simulation results of this study may be helpful in improving the design of the ripple filter. (authors)
Optimal Neutron Source and Beam Shaping Assembly for Boron Neutron Capture Therapy
International Nuclear Information System (INIS)
There were three objectives to this project: (1) The development of the 2-D Swan code for the optimization of the nuclear design of facilities for medical applications of radiation, radiation shields, blankets of accelerator-driven systems, fusion facilities, etc. (2) Identification of the maximum beam quality that can be obtained for Boron Neutron Capture Therapy (BNCT) from different reactor-, and accelerator-based neutron sources. The optimal beam-shaping assembly (BSA) design for each neutron source was also to e obtained. (3) Feasibility assessment of a new neutron source for NCT and other medical and industrial applications. This source consists of a state-of-the-art proton or deuteron accelerator driving and inherently safe, proliferation resistant, small subcritical fission assembly
Optimal Neutron Source and Beam Shaping Assembly for Boron Neutron Capture Therapy
Vujic, J L; Greenspan, E; Guess, S; Karni, Y; Kastenber, W E; Kim, L; Leung, K N; Regev, D; Verbeke, J M; Waldron, W L; Zhu, Y
2003-01-01
There were three objectives to this project: (1) The development of the 2-D Swan code for the optimization of the nuclear design of facilities for medical applications of radiation, radiation shields, blankets of accelerator-driven systems, fusion facilities, etc. (2) Identification of the maximum beam quality that can be obtained for Boron Neutron Capture Therapy (BNCT) from different reactor-, and accelerator-based neutron sources. The optimal beam-shaping assembly (BSA) design for each neutron source was also to e obtained. (3) Feasibility assessment of a new neutron source for NCT and other medical and industrial applications. This source consists of a state-of-the-art proton or deuteron accelerator driving and inherently safe, proliferation resistant, small subcritical fission assembly.
Optimal Neutron Source & Beam Shaping Assembly for Boron Neutron Capture Therapy
Energy Technology Data Exchange (ETDEWEB)
J. Vujic; E. Greenspan; W.E. Kastenber; Y. Karni; D. Regev; J.M. Verbeke, K.N. Leung; D. Chivers; S. Guess; L. Kim; W. Waldron; Y. Zhu
2003-04-30
There were three objectives to this project: (1) The development of the 2-D Swan code for the optimization of the nuclear design of facilities for medical applications of radiation, radiation shields, blankets of accelerator-driven systems, fusion facilities, etc. (2) Identification of the maximum beam quality that can be obtained for Boron Neutron Capture Therapy (BNCT) from different reactor-, and accelerator-based neutron sources. The optimal beam-shaping assembly (BSA) design for each neutron source was also to e obtained. (3) Feasibility assessment of a new neutron source for NCT and other medical and industrial applications. This source consists of a state-of-the-art proton or deuteron accelerator driving and inherently safe, proliferation resistant, small subcritical fission assembly.
International Nuclear Information System (INIS)
The principal aim of this study was to evaluate the feasibility of incorporating four-dimensional (4D)-computed tomography (CT)-based functional information into treatment planning and to evaluate the potential benefits of individualized beam setups to better protect lung functionality in patients with non-small cell lung cancer (NSCLC). Peak-exhale and peak-inhale CT scans were carried out in 16 patients with NSCLC treated with intensity-modulated radiotherapy (IMRT). 4D-CT-based ventilation information was generated from the two sets of CT images using deformable image registration. Four kinds of IMRT plans were generated for each patient: two anatomic plans without incorporation of ventilation information, and two functional plans with ventilation information, using either five equally spaced beams (FESB) or five manually optimized beams (FMOB). The dosimetric parameters of the plans were compared in terms of target and normal tissue structures, with special focus on dose delivered to total lung and functional lung. In both the anatomic and functional plans, the percentages of both the functional and total lung regions irradiated at V5, V10, and V20 (percentage volume irradiated to >5, >10 and >20 Gy, respectively) were significantly lower for FMOB compared with FESB (P < 0.05), but there was no significant difference for V30 (P > 0.05). Compared with FESB, a greater degree of sparing of the functional lung was achieved in functional IMRT plans with optimal beam arrangement, without compromising target volume coverage or the irradiated volume of organs at risk, such as the spinal cord, esophagus, and heart. Pulmonary ventilation image-guided IMRT planning with further optimization of beam arrangements improves the preservation of functional lung in patients with NSCLC
Laser-driven proton beams: Acceleration mechanism, beam optimization, and radiographic applications
Energy Technology Data Exchange (ETDEWEB)
Borghesi, M.; Romagnani, L.; Kar, S.; Wilson, P.A. [School of Mathematics and Physics, The Queen' s University of Belfast (United Kingdom); Cecchetti, C.A. [School of Mathematics and Physics, The Queen' s University of Belfast (United Kingdom); Also with the Intense Laser Irradiation Laboratory, IPCF-CNR, Pisa (Italy); Toncian, T.; Pipahl, A.; Amin, M.; Jung, R.; Osterholz, J.; Willi, O. [Institute for Laser and Plasma Physics, Heinrich Heine University, Dusseldorf (Germany); Fuchs, J.; Audebert, P.; Brambrink, E. [Laboratoire pour l' Utilisation des Lasers Intenses LULI, UMR 7605 CNRS-CEA-Ecole Polytechnique, 91 - Palaiseau (France); Antici, P. [Laboratoire pour l' Utilisation des Lasers Intenses LULI, UMR 7605 CNRS CEA Ecole Polytechnique, 91 - Palaiseau (France); Frascati National Laboratories INFN, Frascati (Italy); Nazarov, W. [School of Chemistry, University of St. Andrews, St. Andrews (United Kingdom); Clarke, R.J.; Notley, M.; Neely, D. [Central Laser Facility, STFC Rutherford Appleton Laboratory, OX Didcot (United Kingdom); Mora, P.; Grismayer, T. [Centre de Physique Theorique, Ecole Polytechnique, CNRS, 91 - Palaiseau (France); Schurtz, G. [Centre d' Etudes des Lasers Intenses et Applications, UMR 5107 University Bordeaux I-CNRS-CEA, 33 - Talence (France); Schiavi, A. [Dipartimento di Energetica, Universita -La Sapienza-, Rome (Italy); Sentoku, Y.; D' Humieres, E. [Physics Department, MS 220, University of Nevada, Reno, NV (United States)
2008-08-15
This paper reviews recent experimental activity in the area of optimization, control, and application of laser-accelerated proton beams, carried out at the Rutherford Appleton Laboratory and the Laboratoire pour l'Utilisation des Lasers Intenses 100 TW facility in France. In particular, experiments have investigated the role of the scale length at the rear of the plasma in reducing target-normal-sheath-acceleration acceleration efficiency. Results match with recent theoretical predictions and provide information in view of the feasibility of proton fast-ignition applications. Experiments aiming to control the divergence of the proton beams have investigated the use of a laser-triggered micro-lens, which employs laser-driven transient electric fields in cylindrical geometry, enabling to focus the emitted protons and select monochromatic beamlets; out of the broad spectrum beam. This approach could be advantageous in view of a variety of applications. The use of laser-driven protons as a particle probe for transient field detection has been developed and applied to a number of experimental conditions. Recent work in this area has focused on the detection of large-scale self-generated magnetic fields in laser-produced plasmas and the investigation of fields associated to the propagation of relativistic electron both on the surface and in the bulk of targets irradiated by high-power laser pulses. (authors)
Optimization of Power Allocation for Multiusers in Multi-Spot-Beam Satellite Communication Systems
Directory of Open Access Journals (Sweden)
Heng Wang
2014-01-01
Full Text Available In recent years, multi-spot-beam satellite communication systems have played a key role in global seamless communication. However, satellite power resources are scarce and expensive, due to the limitations of satellite platform. Therefore, this paper proposes optimizing the power allocation of each user in order to improve the power utilization efficiency. Initially the capacity allocated to each user is calculated according to the satellite link budget equations, which can be achieved in the practical satellite communication systems. The problem of power allocation is then formulated as a convex optimization, taking account of a trade-off between the maximization of the total system capacity and the fairness of power allocation amongst the users. Finally, an iterative algorithm based on the duality theory is proposed to obtain the optimal solution to the optimization. Compared with the traditional uniform resource allocation or proportional resource allocation algorithms, the proposed optimal power allocation algorithm improves the fairness of power allocation amongst the users. Moreover, the computational complexity of the proposed algorithm is linear with both the numbers of the spot beams and users. As a result, the proposed power allocation algorithm is easy to be implemented in practice.
Local-Optimality Guaranties for Optimal Decoding Based on Paths
Halabi, Nissim
2012-01-01
This paper presents a unified analysis framework that captures recent advances in the study of local-optimality characterizations for codes on graphs. These local-optimality characterizations are based on combinatorial structures embedded in the Tanner graph of the code. Local-optimality implies both maximum-likelihood (ML) optimality and linear-programming (LP) decoding optimality. Also, an iterative message-passing decoding algorithm is guaranteed to find the unique locally-optimal codeword, if one exists. We demonstrate this proof technique by considering a definition of local-optimality that is based on the simplest combinatorial structures in Tanner graphs, namely, paths of length $h$. We apply the technique of local optimality to a family of Tanner codes. Inverse polynomial bounds in the code length are proved on the word error probability of LP-decoding for this family of Tanner codes.
A Numerical Method of the Euler-Bernoulli Beam with Optimal Local Kelvin-Voigt Damping
Directory of Open Access Journals (Sweden)
Xin Yu
2014-01-01
Full Text Available This paper deals with the numerical approximation problem of the optimal control problem governed by the Euler-Bernoulli beam equation with local Kelvin-Voigt damping, which is a nonlinear coefficient control problem with control constraints. The goal of this problem is to design a control input numerically, which is the damping and distributes locally on a subinterval of the region occupied by the beam, such that the total energy of the beam and the control on a given time period is minimal. We firstly use the finite element method (FEM to obtain a finite-dimensional model based on the original PDE system. Then, using the control parameterization method, we approximate the finite-dimensional problem by a standard optimal parameter selection problem, which is a suboptimal problem and can be solved numerically by nonlinear mathematical programming algorithm. At last, some simulation studies will be presented by the proposed numerical approximation method in this paper, where the damping controls act on different locations of the Euler-Bernoulli beam.
High dimensional real parameter optimization with teaching learning based optimization
Anima Naik; Suresh Chandra Satapathy; K. Parvathi
2012-01-01
In this paper, a new optimization technique known as Teaching–Learning-Based Optimization (TLBO) is implemented for solving high dimensional function optimization problems. Even though there are several other approaches to address this issue but the cost of computations are more in handling high dimensional problems. In this work we simulate TLBO for high dimensional benchmark function optimizations and compare its results with very widely used alternate techniques like Differential Evolution...
Design of a neutrino source based on beta beams
Wildner, E.; Hansen, C.; Benedetto, E.; Jensen, E.; Stora, T.; Mendonca, T. Melo; Vlachoudis, V.; Bouquerel, E.; Marie-Jeanne, M.; Balint, P.; Fourel, C.; Giraud, J.; Jacob, J.; Lamy, T.; Latrasse, L.; Sortais, P.; Thuillier, T.; Mitrofanov, S.; Loiselet, M.; Keutgen, Th.; Delbar, Th.; Debray, F.; Trophime, C.; Veys, S.; Daversin, C.; Zorin, V.; Izotov, I.; Skalyga, V.; Chancé, A.; Payet, J.; Burt, G.; Dexter, A. C.; Kravchuk, V. L.; Marchi, T.; Cinausero, M.; Gramegna, F.; De Angelis, G.; Prete, G.; Collazuol, G.; Mezzetto, M.; Vardaci, E.; Di Nitto, A.; Brondi, A.; La Rana, G.; Moro, R.; Palladino, V.; Gelli, N.; Mazzocco, M.; Signorini, C.; Hirsh, T. Y.; Hass, M.; Berkovits, D.; Stahl, A.; Schaumann, M.; Wehner, J.
2014-07-01
"Beta beams" produce collimated pure electron (anti)neutrino beams by accelerating beta active ions to high energies and having them decay in a racetrack shaped storage ring of 7 km circumference, the decay ring. EUROnu beta beams are based on CERN infrastructures and existing machines. Using existing machines may be an advantage for the cost evaluation, but will also constrain the physics performance. The isotope pair of choice for the beta beam is He6 and Ne18. However, before the EUROnu studies one of the required isotopes, Ne18, could not be produced in rates that satisfy the needs for physics of the beta beam. Therefore, studies of alternative beta emitters, Li8 and B8, with properties interesting for a beta beam have been proposed and have been studied within EUROnu. These alternative isotopes could be produced by using a small storage ring, in which the beam traverses a target, creating the Li8 and B8 isotopes. This production ring, the injection linac and the target system have been evaluated. Measurements of the cross section of the reactions to produce the beta beam isotopes show interesting results. A device to collect the produced isotopes from the target has been developed and tested. However, the yields of Li8 and B8, using the production ring for production of Li8 and B8, is not yet, according to simulations, giving the rates of isotopes that would be needed. Therefore, a new method of producing the Ne18 isotope has been developed and tested giving good production rates. A 60 GHz ECRIS prototype, the first in the world, was developed and tested for ion production with contributions from EUROnu. The decay ring lattices for the Li8 and B8 have been developed and the lattice for He6 and Ne18 has been optimized to ensure the high intensity ion beam stability.
International Nuclear Information System (INIS)
Stereotactic body radiation therapy (SBRT) is characterized by delivering a high amount of dose in a short period of time. In SBRT the dose is delivered using open fields (e.g., beam’s-eye-view) known as ‘apertures’. Mathematical methods can be used for optimizing treatment planning for delivery of sufficient dose to the cancerous cells while keeping the dose to surrounding organs at risk (OARs) minimal. Two important elements of a treatment plan are quality and delivery time. Quality of a plan is measured based on the target coverage and dose to OARs. Delivery time heavily depends on the number of beams used in the plan as the setup times for different beam directions constitute a large portion of the delivery time. Therefore the ideal plan, in which all potential beams can be used, will be associated with a long impractical delivery time. We use the dose to OARs in the ideal plan to find the plan with the minimum number of beams which is guaranteed to be epsilon-optimal (i.e., a predetermined maximum deviation from the ideal plan is guaranteed). Since the treatment plan optimization is inherently a multi-criteria-optimization problem, the planner can navigate the ideal dose distribution Pareto surface and select a plan of desired target coverage versus OARs sparing, and then use the proposed technique to reduce the number of beams while guaranteeing epsilon-optimality. We use mixed integer programming (MIP) for optimization. To reduce the computation time for the resultant MIP, we use two heuristics: a beam elimination scheme and a family of heuristic cuts, known as ‘neighbor cuts’, based on the concept of ‘adjacent beams’. We show the effectiveness of the proposed technique on two clinical cases, a liver and a lung case. Based on our technique we propose an algorithm for fast generation of epsilon-optimal plans. (paper)
International Nuclear Information System (INIS)
Problems of two-parametric optimization of single-beam gamma absorption concentration meters in the assigned measurement range are considered. It is shown that maximum absolute and relative statistical measurement errors are observed at the measurement range boundaries under any values of variable parameters. Optimization of single-beam gamma absorption concentration meter parameters for a number of binary solutions is performed
Multi-material topology optimization of laminated composite beam cross sections
DEFF Research Database (Denmark)
Blasques, José Pedro Albergaria Amaral; Stolpe, Mathias
2012-01-01
This paper presents a novel framework for simultaneous optimization of topology and laminate properties in structural design of laminated composite beam cross sections. The structural response of the beam is evaluated using a beam finite element model comprising a cross section analysis tool whic...
Beam shaping for laser-based adaptive optics in astronomy
Béchet, Clémentine; Neichel, Benoit; Fesquet, Vincent; González-Núñez, Héctor; Zúñiga, Sebastián; Escarate, Pedro; Guzman, Dani
2014-01-01
The availability and performance of laser-based adaptive optics (AO) systems are strongly dependent on the power and quality of the laser beam before being projected to the sky. Frequent and time-consuming alignment procedures are usually required in the laser systems with free-space optics to optimize the beam. Despite these procedures, significant distortions of the laser beam have been observed during the first two years of operation of the Gemini South multi-conjugate adaptive optics system (GeMS). A beam shaping concept with two deformable mirrors is investigated in order to provide automated optimization of the laser quality for astronomical AO. This study aims at demonstrating the correction of quasi-static aberrations of the laser, in both amplitude and phase, testing a prototype of this two-deformable mirror concept on GeMS. The paper presents the results of the preparatory study before the experimental phase. An algorithm to control amplitude and phase correction, based on phase retrieval techniques...
International Nuclear Information System (INIS)
Inverse planning in external beam radiotherapy often requires a scalar objective function that incorporates importance factors to mimic the planner's preferences between conflicting objectives. Defining those importance factors is not straightforward, and frequently leads to an iterative process in which the importance factors become variables of the optimization problem. In order to avoid this drawback of inverse planning, optimization using algorithms more suited to multiobjective optimization, such as evolutionary algorithms, has been suggested. However, much inverse planning software, including one based on simulated annealing developed at our institution, does not include multiobjective-oriented algorithms. This work investigates the performance of a modified simulated annealing algorithm used to drive aperture-based intensity-modulated radiotherapy inverse planning software in a multiobjective optimization framework. For a few test cases involving gastric cancer patients, the use of this new algorithm leads to an increase in optimization speed of a little more than a factor of 2 over a conventional simulated annealing algorithm, while giving a close approximation of the solutions produced by a standard simulated annealing. A simple graphical user interface designed to facilitate the decision-making process that follows an optimization is also presented
LASER-BASED PROFILE MONITOR FOR ELECTRON BEAMS
International Nuclear Information System (INIS)
High performance TeV energy electron / positron colliders (LC) are the first machines to require online, non-invasive beam size monitors for micron and sub-micron for beam phase space optimization. Typical beam densities in the LC are well beyond the threshold density for single pulse melting and vaporization of any material, making conventional wire scanners ineffective. Using a finely focused, diffraction limited high power laser, it is possible to devise a sampling profile monitor that, in operation, resembles a wire scanner. Very high resolution laser-based profile monitors have been developed and tested, first at FFTB (SLAC) and later at SLC and ATF. The monitor has broad applicability and we review here the technology, application and status of ongoing research programs
Optimal Timer Based Selection Schemes
Shah, Virag; Yim, Raymond
2009-01-01
Timer-based mechanisms are often used to help a given (sink) node select the best helper node among many available nodes. Specifically, a node transmits a packet when its timer expires, and the timer value is a monotone non-increasing function of its local suitability metric. The best node is selected successfully if no other node's timer expires within a 'vulnerability' window after its timer expiry, and so long as the sink can hear the available nodes. In this paper, we show that the optimal metric-to-timer mapping that (i) maximizes the probability of success or (ii) minimizes the average selection time subject to a minimum constraint on the probability of success, maps the metric into a set of discrete timer values. We specify, in closed-form, the optimal scheme as a function of the maximum selection duration, the vulnerability window, and the number of nodes. An asymptotic characterization of the optimal scheme turns out to be elegant and insightful. For any probability distribution function of the metri...
Performance Modeling and Optimization of a High Energy Colliding Beam Simulation Code
International Nuclear Information System (INIS)
An accurate modeling of the beam-beam interaction is essential to maximizing the luminosity in existing and future colliders. BeamBeam3D was the first parallel code that can be used to study this interaction fully self-consistently on high-performance computing platforms. Various all-to-all personalized communication (AAPC) algorithms dominate its communication patterns, for which we developed a sequence of performance models using a series of micro-benchmarks. We find that for SMP based systems the most important performance constraint is node-adapter contention, while for 3D-Torus topologies good performance models are not possible without considering link contention. The best average model prediction error is very low on SMP based systems with of 3% to 7%. On torus based systems errors of 29% are higher but optimized performance can again be predicted within 8% in some cases. These excellent results across five different systems indicate that this methodology for performance modeling can be applied to a large class of algorithms
Data consistency-driven scatter kernel optimization for x-ray cone-beam CT
Kim, Changhwan; Park, Miran; Sung, Younghun; Lee, Jaehak; Choi, Jiyoung; Cho, Seungryong
2015-08-01
Accurate and efficient scatter correction is essential for acquisition of high-quality x-ray cone-beam CT (CBCT) images for various applications. This study was conducted to demonstrate the feasibility of using the data consistency condition (DCC) as a criterion for scatter kernel optimization in scatter deconvolution methods in CBCT. As in CBCT, data consistency in the mid-plane is primarily challenged by scatter, we utilized data consistency to confirm the degree of scatter correction and to steer the update in iterative kernel optimization. By means of the parallel-beam DCC via fan-parallel rebinning, we iteratively optimized the scatter kernel parameters, using a particle swarm optimization algorithm for its computational efficiency and excellent convergence. The proposed method was validated by a simulation study using the XCAT numerical phantom and also by experimental studies using the ACS head phantom and the pelvic part of the Rando phantom. The results showed that the proposed method can effectively improve the accuracy of deconvolution-based scatter correction. Quantitative assessments of image quality parameters such as contrast and structure similarity (SSIM) revealed that the optimally selected scatter kernel improves the contrast of scatter-free images by up to 99.5%, 94.4%, and 84.4%, and of the SSIM in an XCAT study, an ACS head phantom study, and a pelvis phantom study by up to 96.7%, 90.5%, and 87.8%, respectively. The proposed method can achieve accurate and efficient scatter correction from a single cone-beam scan without need of any auxiliary hardware or additional experimentation.
Data consistency-driven scatter kernel optimization for x-ray cone-beam CT
International Nuclear Information System (INIS)
Accurate and efficient scatter correction is essential for acquisition of high-quality x-ray cone-beam CT (CBCT) images for various applications. This study was conducted to demonstrate the feasibility of using the data consistency condition (DCC) as a criterion for scatter kernel optimization in scatter deconvolution methods in CBCT. As in CBCT, data consistency in the mid-plane is primarily challenged by scatter, we utilized data consistency to confirm the degree of scatter correction and to steer the update in iterative kernel optimization. By means of the parallel-beam DCC via fan-parallel rebinning, we iteratively optimized the scatter kernel parameters, using a particle swarm optimization algorithm for its computational efficiency and excellent convergence. The proposed method was validated by a simulation study using the XCAT numerical phantom and also by experimental studies using the ACS head phantom and the pelvic part of the Rando phantom. The results showed that the proposed method can effectively improve the accuracy of deconvolution-based scatter correction. Quantitative assessments of image quality parameters such as contrast and structure similarity (SSIM) revealed that the optimally selected scatter kernel improves the contrast of scatter-free images by up to 99.5%, 94.4%, and 84.4%, and of the SSIM in an XCAT study, an ACS head phantom study, and a pelvis phantom study by up to 96.7%, 90.5%, and 87.8%, respectively. The proposed method can achieve accurate and efficient scatter correction from a single cone-beam scan without need of any auxiliary hardware or additional experimentation. (paper)
International Nuclear Information System (INIS)
For the beam splitter attack strategy against quantum key distribution using two-mode squeezed states, the analytical expression of the optimal beam splitter parameter is provided in this paper by applying the Shannon information theory. The theoretical secret information rate after error correction and privacy amplification is given in terms of the squeezed parameter and channel parameters. The results show that the two-mode squeezed state quantum key distribution is secure against an optimal beam splitter attack
4D optimization of scanned ion beam tracking therapy for moving tumors
Eley, John Gordon; Newhauser, Wayne David; Lüchtenborg, Robert; Graeff, Christian; Bert, Christoph
2014-07-01
Motion mitigation strategies are needed to fully realize the theoretical advantages of scanned ion beam therapy for patients with moving tumors. The purpose of this study was to determine whether a new four-dimensional (4D) optimization approach for scanned-ion-beam tracking could reduce dose to avoidance volumes near a moving target while maintaining target dose coverage, compared to an existing 3D-optimized beam tracking approach. We tested these approaches computationally using a simple 4D geometrical phantom and a complex anatomic phantom, that is, a 4D computed tomogram of the thorax of a lung cancer patient. We also validated our findings using measurements of carbon-ion beams with a motorized film phantom. Relative to 3D-optimized beam tracking, 4D-optimized beam tracking reduced the maximum predicted dose to avoidance volumes by 53% in the simple phantom and by 13% in the thorax phantom. 4D-optimized beam tracking provided similar target dose homogeneity in the simple phantom (standard deviation of target dose was 0.4% versus 0.3%) and dramatically superior homogeneity in the thorax phantom (D5-D95 was 1.9% versus 38.7%). Measurements demonstrated that delivery of 4D-optimized beam tracking was technically feasible and confirmed a 42% decrease in maximum film exposure in the avoidance region compared with 3D-optimized beam tracking. In conclusion, we found that 4D-optimized beam tracking can reduce the maximum dose to avoidance volumes near a moving target while maintaining target dose coverage, compared with 3D-optimized beam tracking.
International Nuclear Information System (INIS)
Cosy Juelich is a cooler synchrotron and storage ring with a proton momentum range 270 to 3300 MeV/c. It has been conceived to deliver high percision beams for medium energy physics. For that purpose, electron and stochasd phase space cooling is available at COSY. At the present the beam is used at three internal and three external target places. The beam line to the Time Of Flight spectrometer (TOF) consists of four sections. The first section I matches the COSY beam properties to following sections to transport the beam in an economic way to the target area. In the next two sections, II and lit, the beam is handled almost without losses. The last section is used to fit the beam to the experiment requirements. The optimization of beam lines for extracted particles from accelerator facilities requires the knowledge of beam parameters, A method for phase space measurement depends on the thin lenses approximation is developed at COSY. This method depends on imaging by quadrupole lenses of the beam profiles at arbitrary positions along the beam axis on a multi wire chamber. The emittances of the extracted COSY beam, without phase space cooling, were determined by the imaging method at several energies. The emittances were determined to be around 3 π [mm mrad]. The waist positions, and the beam extensions in horizontal and vertical planes were determined. It Is found out that the waist positions are rather independent of the beam energy. To get a beam spot on the target of radius less than 1 mm. and to decrease the halo near the TOF spectrometer the beam was successfully limited in emittance with the upstream dipoles far away from the target, Some properties of the beam were investigated and optimized In me target region with the help of veto counters (scintillator rings), a start detector and a strip hodoscope. Near the target 98% of the beam intensity passes through the 2 mm central hole of the veto detector. Also measurement of the beam position and a fine
High dimensional real parameter optimization with teaching learning based optimization
Directory of Open Access Journals (Sweden)
Anima Naik
2012-10-01
Full Text Available In this paper, a new optimization technique known as Teaching–Learning-Based Optimization (TLBO is implemented for solving high dimensional function optimization problems. Even though there are several other approaches to address this issue but the cost of computations are more in handling high dimensional problems. In this work we simulate TLBO for high dimensional benchmark function optimizations and compare its results with very widely used alternate techniques like Differential Evolution (DE and Particle Swarm Optimization (PSO. Results clearly reveal that TLBO is able to address the computational cost issue for all simulated functions to a large dimensions compared to other two techniques.
Optical encoder based on a nondiffractive beam
International Nuclear Information System (INIS)
Optical encoders are used in industrial and laboratory motion equipment to measure rotations and linear displacements. We introduce a design of an optical encoder based on a nondiffractive beam. We expect that the invariant profile and radial symmetry of the nondiffractive beam provide the design with remarkable tolerance to mechanical perturbations. We experimentally demonstrate that the proposed design generates a suitable output sinusoidal signal with low harmonic distortion. Moreover, we present a numerical model of the system based on the angular spectrum approximation whose predictions are in excellent agreement with the experimental results
Duality based contact shape optimization
DEFF Research Database (Denmark)
Vondrák, Vít; Dostal, Zdenek; Rasmussen, John
An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization.......An implementation of semi-analytic method for the sensitivity analysis in contact shape optimization without friction is described. This method is then applied to the contact shape optimization....
Optimal control methods for vertical and horizontal beam dynamics
International Nuclear Information System (INIS)
An application of the Macro Fiber Composite (MFC) actuators for damping of a composite beam is presented in this paper. The effectiveness of vibration reduction by a selected control method is tested for vertical and horizontal position of the beam. The original model has been studied numerically by using Galerkin's discretisation method. The numerical results for the vertical and horizontal beams are compared.
Optimization of a charge-state analyzer for ECRIS beams
Saminathan, S; Kremers, H R; Mironov, V; Mulder, J; Brandenburg, S
2012-01-01
A detailed experimental and simulation study of the extraction of a 24 keV He-ion beam from an ECR ion source and the subsequent beam transport through an analyzing magnet is presented. We find that such a slow ion beam is very sensitive to space-charge forces, but also that the neutralization of the beam's space charge by secondary electrons is virtually complete for beam currents up to at least 0.5 mA. The beam emittance directly behind the extraction system is 65 pi mm mrad and is determined by the fact that the ion beam is extracted in the strong magnetic fringe field of the ion source. The relatively large emittance of the beam and its non-paraxiality lead, in combination with a relatively small magnet gap, to significant beam losses and a five-fold increase of the effective beam emittance during its transport through the analyzing magnet. The calculated beam profile and phase-space distributions in the image plane of the analyzing magnet agree well with measurements. The kinematic and magnet aberrations...
A bee colony optimization-based approach for binary optimization
Kıran, Mustafa Servet; Gündüz, Mesut
2013-01-01
The bee colony optimization (BCO) algorithm, one of the swarm intelligence algorithms, is a population based iterative search algorithm. Being inspired by collective bee intelligence, BCO has been proposed for solving discrete optimization problems such as travelling salesman problem. The BCO uses constructive approach for creating a feasible solution for the discrete optimization problems but in this study, we used the solution improvement technique due to nature of the uncapacitated facilit...
Lifecycle-Based Swarm Optimization Method for Numerical Optimization
Hai Shen; Yunlong Zhu; Xiaodan Liang
2014-01-01
Bioinspired optimization algorithms have been widely used to solve various scientific and engineering problems. Inspired by biological lifecycle, this paper presents a novel optimization algorithm called lifecycle-based swarm optimization (LSO). Biological lifecycle includes four stages: birth, growth, reproduction, and death. With this process, even though individual organism died, the species will not perish. Furthermore, species will have stronger ability of adaptation to the environment a...
Reliability-based optimization of engineering structures
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard
The theoretical basis for reliability-based structural optimization within the framework of Bayesian statistical decision theory is briefly described. Reliability-based cost benefit problems are formulated and exemplitied with structural optimization. The basic reliability-based optimization...... problems are generalized to the following extensions: interactive optimization, inspection and repair costs, systematic reconstruction, re-assessment of existing structures. Illustrative examples are presented including a simple introductory example, a decision problem related to bridge re-assessment and a...
Semiautomatic beam-based LHC collimator alignment
Valentino, Gianluca; Bruce, Roderik; Wollmann, Daniel; Sammut, Nicholas; Rossi, Adriana; Redaelli, Stefano
2012-01-01
Full beam-based alignment of the LHC collimation system was a time-consuming procedure (up to 28 hours) as the collimators were set up manually. A yearly alignment campaign has been sufficient for now, although in the future due to tighter tolerances this may lead to a decrease in the cleaning efficiency if machine parameters such as the beam orbit drift over time. Automating the collimator setup procedure can reduce the beam time for collimator setup and allow for more frequent alignments, therefore reducing the risk of performance degradation. This article describes the design and testing of a semiautomatic algorithm as a first step towards a fully automatic setup procedure. The parameters used to measure the accuracy and performance of the alignment are defined and determined from experimental data. A comparison of these measured parameters at 450 GeV and 3.5 TeV with manual and semiautomatic alignment is provided.
Beam trial and operation optimization of 10 MeV industrial electron Linac
International Nuclear Information System (INIS)
A 10 MeV travelling wave industrial (TWINDUS) electron linac suitable for radiation processing applications is under development at RRCAT. The linac is designed and developed indigenously to deliver beam power of 6 kW at energy level of 10 MeV. It consists of various subsystems such as accelerating structure, electron gun, microwave system, control system, beam injection and focusing system, vacuum system, beam diagnostic and measurement system and safety system. After independent subsystem level testing, all the systems were integrated and beam trial experiments were taken up in a shielded vault after obtaining due approval from Atomic Energy Regulatory Board (AERB). Optimization and harmonization of the operating parameters of all these sub-systems is carried-out in order to achieve the desired electron beam current and power. This paper describes the results of series of beam trial experiments carried out to optimize operation parameters for demonstrating operation at 4.2 kW beam power
The Ontology of Knowledge Based Optimization
Nasution, Mahyuddin K. M.
2012-01-01
Optimization has been becoming a central of studies in mathematic and has many areas with different applications. However, many themes of optimization came from different area have not ties closing to origin concepts. This paper is to address some variants of optimization problems using ontology in order to building basic of knowledge about optimization, and then using it to enhance strategy to achieve knowledge based optimization.
DESIGN OF A SHAPED BEAM BASE STATION ANTENNA USING GENETIC ALGORITHM
Institute of Scientific and Technical Information of China (English)
Liu Ying; Bu Antao; Gong Shuxi; Shen Zongzhen; Xiao Liangyong
2003-01-01
Genetic algorithm is used to optimize a base station antenna in order to achieve a shaped beam in a frequency band. During the optimization process, different antenna models have been evaluated using the Method of Moment (MoM). As a result of this optimization, a shaped beam antenna with suppressed sidelobe smaller than -18dB, backlobe smaller than -30dB and filled null point larger than -15dB is achieved. The proposed method is closer to reality compared with previous methods and can be used to optimize complicated antennas. The result is very useful for engineering and theoretical analysis.
Multiobjective Optimization Based Vessel Collision Avoidance Strategy Optimization
Directory of Open Access Journals (Sweden)
Qingyang Xu
2014-01-01
Full Text Available The vessel collision accidents cause a great loss of lives and property. In order to reduce the human fault and greatly improve the safety of marine traffic, collision avoidance strategy optimization is proposed to achieve this. In the paper, a multiobjective optimization algorithm NSGA-II is adopted to search for the optimal collision avoidance strategy considering the safety as well as economy elements of collision avoidance. Ship domain and Arena are used to evaluate the collision risk in the simulation. Based on the optimization, an optimal rudder angle is recommended to navigator for collision avoidance. In the simulation example, a crossing encounter situation is simulated, and the NSGA-II searches for the optimal collision avoidance operation under the Convention on the International Regulations for Preventing Collisions at Sea (COLREGS. The simulation studies exhibit the validity of the method.
Concentric Circular Antenna Array Synthesis Using Biogeography Based Optimization
Directory of Open Access Journals (Sweden)
Urvinder Singh
2012-03-01
Full Text Available Biogeography based optimization (BBO is a new stochastic force based on the science of biogeography. Biogeography is the schoolwork of geographical allotment of biological organisms. BBO utilizes migration operator to share information between the problem solutions. The problem solutions are known as habitats and sharing of features is called migration. In this paper, BBO algorithm is developed to optimize the current excitations of concentric circular antenna arrays (CCAA. Concentric Circular Antenna Array (CCAA has numerous attractive features that make it essential in mobile and communication applications. The goal of the optimization is to reduce the side lobe levels and the primary lobe beam width as much as possible. To confirm the capabilities of BBO, three different CCAA antennas of different sizes are taken. The results obtained by BBO are compared with the Real coded Genetic Algorithm (RGA, Craziness based Particle Swarm Optimization (CRPSO and Hybrid Evolutionary Programming (HEP.
Liquid Crystal-based Beam Steering Technologies for NASA Applications
Pouch, John; Nguyen, Hung; Miranda, Felix; Bos, Philip; Lavrentovich, Oleg; Wang, Xinghua; Pishnyak, Oleg; Kreminska, Liubov; Golovin, Andrii
2006-01-01
Liquid crystal-based beam steering devices can provide electronic beam scanning to angles above 1 milliradian, sub-microradian beam pointing accuracy, as well as wave-front correction to maintain output optical beam quality. The liquid crystal technology effort will be summarized, and the potential application of the resulting devices to NASA space-based scenarios will be described.
Drilling Path Optimization Based on Particle Swarm Optimization Algorithm
Institute of Scientific and Technical Information of China (English)
ZHU Guangyu; ZHANG Weibo; DU Yuexiang
2006-01-01
This paper presents a new approach based on the particle swarm optimization (PSO) algorithm for solving the drilling path optimization problem belonging to discrete space. Because the standard PSO algorithm is not guaranteed to be global convergence or local convergence, based on the mathematical algorithm model, the algorithm is improved by adopting the method of generate the stop evolution particle over again to get the ability of convergence to the global optimization solution. And the operators are improved by establishing the duality transposition method and the handle manner for the elements of the operator, the improved operator can satisfy the need of integer coding in drilling path optimization. The experiment with small node numbers indicates that the improved algorithm has the characteristics of easy realize, fast convergence speed, and better global convergence characteristics, hence the new PSO can play a role in solving the problem of drilling path optimization in drilling holes.
Reliability-based concurrent subspace optimization method
Institute of Scientific and Technical Information of China (English)
FAN Hui; LI Wei-ji
2008-01-01
To avoid the high computational cost and much modification in the process of applying traditional re-liability-based design optimization method, a new reliability-based concurrent subspace optimization approach is proposed based on the comparison and analysis of the existing muhidisciplinary optimization techniques and reli-ability assessment methods. It is shown through a canard configuration optimization for a three-surface transport that the proposed method is computationally efficient and practical with the least modification to the current de-terministic optimization process.
International Nuclear Information System (INIS)
Purpose: To investigate development of a recipe for the creation of a beam angle class solution (CS) for noncoplanar prostate stereotactic body radiation therapy to replace time-consuming individualized beam angle selection (iBAS) without significant loss in plan quality, using the in-house “Erasmus-iCycle” optimizer for fully automated beam profile optimization and iBAS. Methods and Materials: For 30 patients, Erasmus-iCycle was first used to generate 15-, 20-, and 25-beam iBAS plans for a CyberKnife equipped with a multileaf collimator. With these plans, 6 recipes for creation of beam angle CSs were investigated. Plans of 10 patients were used to create CSs based on the recipes, and the other 20 to independently test them. For these tests, Erasmus-iCycle was also used to generate intensity modulated radiation therapy plans for the fixed CS beam setups. Results: Of the tested recipes for CS creation, only 1 resulted in 15-, 20-, and 25-beam noncoplanar CSs without plan deterioration compared with iBAS. For the patient group, mean differences in rectum D1cc, V60GyEq, V40GyEq, and Dmean between 25-beam CS plans and 25-beam plans generated with iBAS were 0.2 ± 0.4 Gy, 0.1% ± 0.2%, 0.2% ± 0.3%, and 0.1 ± 0.2 Gy, respectively. Differences between 15- and 20-beam CS and iBAS plans were also negligible. Plan quality for CS plans relative to iBAS plans was also preserved when narrower planning target volume margins were arranged and when planning target volume dose inhomogeneity was decreased. Using a CS instead of iBAS reduced the computation time by a factor of 14 to 25, mainly depending on beam number, without loss in plan quality. Conclusions: A recipe for creation of robust beam angle CSs for robotic prostate stereotactic body radiation therapy has been developed. Compared with iBAS, computation times decreased by a factor 14 to 25. The use of a CS may avoid long planning times without losses in plan quality
Energy Technology Data Exchange (ETDEWEB)
Rossi, Linda, E-mail: l.rossi@erasmusmc.nl; Breedveld, Sebastiaan; Aluwini, Shafak; Heijmen, Ben
2015-07-15
Purpose: To investigate development of a recipe for the creation of a beam angle class solution (CS) for noncoplanar prostate stereotactic body radiation therapy to replace time-consuming individualized beam angle selection (iBAS) without significant loss in plan quality, using the in-house “Erasmus-iCycle” optimizer for fully automated beam profile optimization and iBAS. Methods and Materials: For 30 patients, Erasmus-iCycle was first used to generate 15-, 20-, and 25-beam iBAS plans for a CyberKnife equipped with a multileaf collimator. With these plans, 6 recipes for creation of beam angle CSs were investigated. Plans of 10 patients were used to create CSs based on the recipes, and the other 20 to independently test them. For these tests, Erasmus-iCycle was also used to generate intensity modulated radiation therapy plans for the fixed CS beam setups. Results: Of the tested recipes for CS creation, only 1 resulted in 15-, 20-, and 25-beam noncoplanar CSs without plan deterioration compared with iBAS. For the patient group, mean differences in rectum D{sub 1cc}, V{sub 60GyEq}, V{sub 40GyEq}, and D{sub mean} between 25-beam CS plans and 25-beam plans generated with iBAS were 0.2 ± 0.4 Gy, 0.1% ± 0.2%, 0.2% ± 0.3%, and 0.1 ± 0.2 Gy, respectively. Differences between 15- and 20-beam CS and iBAS plans were also negligible. Plan quality for CS plans relative to iBAS plans was also preserved when narrower planning target volume margins were arranged and when planning target volume dose inhomogeneity was decreased. Using a CS instead of iBAS reduced the computation time by a factor of 14 to 25, mainly depending on beam number, without loss in plan quality. Conclusions: A recipe for creation of robust beam angle CSs for robotic prostate stereotactic body radiation therapy has been developed. Compared with iBAS, computation times decreased by a factor 14 to 25. The use of a CS may avoid long planning times without losses in plan quality.
BEAM-LOSS DRIVEN DESIGN OPTIMIZATION FOR THE SPALLATION NEUTRON SOURCE (SNS) RING.
Energy Technology Data Exchange (ETDEWEB)
WEI,J.; BEEBE-WANG,J.; BLASKIEWICZ,M.; CAMERON,P.; DANBY,G.; GARDNER,C.J.; JACKSON,J.; LEE,Y.Y.; LUDEWIG,H.; MALITSKY,N.; RAPARIA,D.; TSOUPAS,N.; WENG,W.T.; ZHANG,S.Y.
1999-03-29
This paper summarizes three-stage design optimization for the Spallation Neutron Source (SNS) ring: linear machine design (lattice, aperture, injection, magnet field errors and misalignment), beam core manipulation (painting, space charge, instabilities, RF requirements), and beam halo consideration (collimation, envelope variation, e-p issues etc.).
Production Planning Based on BOM Optimization
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
According to a prototype enterprise, a rulebased Bill of Materials (BOM) structure is designed in order to get optimal design and management of product BOM. The constraint rules and optional objects for product data structure optimization are considered by associating customer demands with product BOM. Furthermore, the functional model of production planning system for assembling enterprise is given based on customization and BOM optimization.
Interactive Reliability-Based Optimal Design
DEFF Research Database (Denmark)
Sørensen, John Dalsgaard; Thoft-Christensen, Palle; Siemaszko, A.;
1994-01-01
Interactive design/optimization of large, complex structural systems is considered. The objective function is assumed to model the expected costs. The constraints are reliability-based and/or related to deterministic code requirements. Solution of this optimization problem is divided in four main...... used in interactive optimization....
International Nuclear Information System (INIS)
Purpose: Station Parameter Optimized Radiation Therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital LINACs, in which the station parameters of a delivery system, (such as aperture shape and weight, couch position/angle, gantry/collimator angle) are optimized altogether. SPORT promises to deliver unprecedented radiation dose distributions efficiently, yet there does not exist any optimization algorithm to implement it. The purpose of this work is to propose an optimization algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: We build a mathematical model whose variables are beam angles (including non-coplanar and/or even nonisocentric beams) and aperture shapes. To solve the resulting large scale optimization problem, we devise an exact, convergent and fast optimization algorithm by integrating three advanced optimization techniques named column generation, gradient method, and pattern search. Column generation is used to find a good set of aperture shapes as an initial solution by adding apertures sequentially. Then we apply the gradient method to iteratively improve the current solution by reshaping the aperture shapes and updating the beam angles toward the gradient. Algorithm continues by pattern search method to explore the part of the search space that cannot be reached by the gradient method. Results: The proposed technique is applied to a series of patient cases and significantly improves the plan quality. In a head-and-neck case, for example, the left parotid gland mean-dose, brainstem max-dose, spinal cord max-dose, and mandible mean-dose are reduced by 10%, 7%, 24% and 12% respectively, compared to the conventional VMAT plan while maintaining the same PTV coverage. Conclusion: Combined use of column generation, gradient search and pattern search algorithms provide an effective way to optimize simultaneously the large collection of station parameters and significantly improves
Energy Technology Data Exchange (ETDEWEB)
Zarepisheh, M; Li, R; Xing, L [Stanford UniversitySchool of Medicine, Stanford, CA (United States); Ye, Y [Stanford Univ, Management Science and Engineering, Stanford, Ca (United States); Boyd, S [Stanford University, Electrical Engineering, Stanford, CA (United States)
2014-06-01
Purpose: Station Parameter Optimized Radiation Therapy (SPORT) was recently proposed to fully utilize the technical capability of emerging digital LINACs, in which the station parameters of a delivery system, (such as aperture shape and weight, couch position/angle, gantry/collimator angle) are optimized altogether. SPORT promises to deliver unprecedented radiation dose distributions efficiently, yet there does not exist any optimization algorithm to implement it. The purpose of this work is to propose an optimization algorithm to simultaneously optimize the beam sampling and aperture shapes. Methods: We build a mathematical model whose variables are beam angles (including non-coplanar and/or even nonisocentric beams) and aperture shapes. To solve the resulting large scale optimization problem, we devise an exact, convergent and fast optimization algorithm by integrating three advanced optimization techniques named column generation, gradient method, and pattern search. Column generation is used to find a good set of aperture shapes as an initial solution by adding apertures sequentially. Then we apply the gradient method to iteratively improve the current solution by reshaping the aperture shapes and updating the beam angles toward the gradient. Algorithm continues by pattern search method to explore the part of the search space that cannot be reached by the gradient method. Results: The proposed technique is applied to a series of patient cases and significantly improves the plan quality. In a head-and-neck case, for example, the left parotid gland mean-dose, brainstem max-dose, spinal cord max-dose, and mandible mean-dose are reduced by 10%, 7%, 24% and 12% respectively, compared to the conventional VMAT plan while maintaining the same PTV coverage. Conclusion: Combined use of column generation, gradient search and pattern search algorithms provide an effective way to optimize simultaneously the large collection of station parameters and significantly improves
International Nuclear Information System (INIS)
Ion beam sources cover a broad spectrum of scientific and technical applications delivering ion currents between less than 1 mA and about 100 A at acceleration voltages between 100 V and 100 kV. The ions are mostly generated by electron collisions in a gas discharge and then extracted from the discharge plasma, focused and post-accelerated by single- or multi-aperture electrode systems. Some important applications require the neutralization of the exhausted beam either by charge exchange or by admixture of electrons. In the first part of the paper, the theory of ionization by electron impact, the energy and carrier balances in the plasma, and the extraction and focusing mechanisms will be outlined. The principles of the preferred gas discharges and of the ion beam sources based on them are discussed; i.e. of the Penning, bombardment, arc, duoplasmatron, radio frequency, and microwave types. In the second part of the paper, the special requirements of the different applications are described together with the related source hardware. One distinguishes: 1. Single-aperture ion sources producing protons, heavy ions, isotope ions, etc. for particle accelerators, ion microprobes, mass spectrometers, isotope separators, etc.; quality determinative quantities are brightness, emittance, energy width, etc. 2. Broad-beam multi-aperture injector sources for fusion machines with positive or negative deuterium ions; very high beam densities, small portions of molecular ions, flat beam profiles with small divergence angles, etc. are required. 3. Broad-beam multi-aperture ion thrusters for space propulsion operated with singly charged xenon ions; high efficiencies, reliable operation, and long lifetimes are most important. Spin-offs are applied in industry for material processing. Referring to these applications, the following sources will be described in some detail: 1. Cold cathode and filament driven sources, capillary arc and plasmatron types, microwave and ECR-sources. 2
Optimization of steady-state beam-driven tokamak reactors
International Nuclear Information System (INIS)
Recent developments in neutral beam technology prompt us to reconsider the prospects for steady-state tokamak reactors. A mathematical reactor model is developed that includes the physics of beam-driven currents and reactor power balance, as well as reactor and beam system costs. This model is used to find the plasma temperatures that minimize the reactor cost per unit of net electrical output. The optimum plasma temperatures are nearly independent of β and are roughly twice as high as the optimum temperatures for ignited reactors. If beams of neutral deuterium atoms with near-optimum energies of 1 to 2 MeV are used to drive the current in a reactor the size of the International Tokamak Reactor, then the optimum temperatures are typically T /SUB e/ approx. = 12 to 15 keV and T /SUB i/ approx. = 17 to 21 keV for a wide range of model parameters. Net electrical output rises rapidly with increasing deuterium beam energy for E /SUB b/ less than or equal to 400 keV, but rises only slowly above E /SUB b/ about 1 MeV. We estimate that beam-driven steady-state reactors could be economically competitive with pulsed-ignition reactors if cyclic-loading problems limit the toroidal magnetic field strength of pulsed reactors to less than or equal to 85% of that allowed in steady-state reactors
Optimization of steady-state beam-driven tokamak reactors
International Nuclear Information System (INIS)
Recent developments in neutral beam technology prompt us to reconsider the prospects for steady-state tokamak reactors. A mathematical reactor model is developed which includes the physics of beam-driven currents and reactor power balance, as well as reactor and beam system costs. This model is used to find the plasma temperatures which minimize the reactor cost per unit of net electrical output. The optimum plasma temperatures are nearly independent of β and are roughly twice as high as the optimum temperatures for ignited reactors. If beams of neutral deuterium atoms with near-optimum energies of 1 to 2 MeV are used to drive the current in an INTOR-sized reactor, then the optimum temperatures are typically T/sub e/ approx. = 12 to 15 keV and T/sub i/ approx. = keV for a wide range of model parameters. Net electrical output rises rapidly with increasing deuterium beam energy for E/sub b/ less than or equal to 400 keV, but rises only slowly above E/sub b/ approx. 1 MeV. We estimate that beam-driven steady-state reactors could be economically competitive with pulsed-ignition reactors if cyclic-loading problems limit the toroidal magnetic field strength of pulsed reactors to less than or equal to 85% of that allowed in steady-state reactors
An Optimal Beamforming Algorithm for Phased-Array Antennas Used in Multi-Beam Spaceborne Radiometers
DEFF Research Database (Denmark)
Iupikov, O. A.; Ivashina, M. V.; Pontoppidan, K.; Cappellin, C.; Skou, Niels; Søbjærg, Sten Schmidl; Ihle, A.; Hartmann, D.; 't Klooster, K. v.; Nielsen, P. H.
2015-01-01
Strict requirements for future spaceborne ocean missions using multi-beam radiometers call for new antenna technologies, such as digital beamforming phased arrays. In this paper, we present an optimal beamforming algorithm for phased-array antenna systems designed to operate as focal plane arrays...... a FPA feeding a torus reflector antenna (designed under the contract with the European Space Agency) and tested for multiple beams. The results demonstrate an improved performance in terms of the optimized beam characteristics, yielding much higher spatial and radiometric resolution as well as much...
International Nuclear Information System (INIS)
A second order beam transport design code with parametric optimization is described. The code analyzes the transport of charged particle beams through a user defined magnet system. The magnet system parameters are varied (within user defined limits) until the properties of the transported beam and/or the system transport matrix match those properties requested by the user. The code uses matrix formalism to represent the transport elements and optimization is achieved using the variable metric method. Any constraints that can be expressed algebraically may be included by the user as part of his design. Instruction in the use of the program is given. (auth)
International Nuclear Information System (INIS)
Knowledge-based optimization in external radiation therapy: association of an expert-system and a numerical optimization technique in the treatment of nasopharyngeal carcinomas. Optimization of radiation therapy in nasopharyngeal carcinoma is particularly complex due to both the proximity of at risk organs and the high dose that has to be delivered. To obtain an optimal dose distribution, a knowledge-based optimization technique has been designed that associates an expert-system, named CAVCAV, with numeric optimization (gradient projection method). Based on clinical and physical criteria, CAVCAV determines the geometric characteristics of the radiation fields (beam direction, location and shape of the shielding blocks) for the three stages of radiation therapy of nasopharyngeal carcinomas. Stage 2-treatment fields proposed by CAVCAV, though not perfectly adapted to the patient, are mathematically (beam weights, beam directions, isocenter position) and geometrically (adaptation of fields and shape of blocks by virtual simulation) optimized. (author)
EDITORIAL: Negative ion based neutral beam injection
Hemsworth, R. S.
2006-06-01
It is widely recognized that neutral beam injection (NBI), i.e. the injection of high energy, high power, beams of H or D atoms, is a flexible and reliable system that has been the main heating system on a large variety of fusion devices, and NBI has been chosen as one of the three heating schemes of the International Tokomak Reactor (ITER). To date, all the NBI systems but two have been based on the neutralization (in a simple gas target) of positive hydrogen or deuterium ions accelerated to 1 MeV/nucleon. Unfortunately H- and D- are difficult to create, and the very characteristic that makes them attractive, the ease with which the electron is detached from the ion, means that it is difficult to create high concentrations or fluxes of them, and it is difficult to avoid substantial, collisional, losses in the extraction and acceleration processes. However, there has been impressive progress in negative ion sources and accelerators over the past decade, as demonstrated by the two pioneering, operational, multi-megawatt, negative ion based, NBI systems at LHD (180 keV, H0) and JT-60U (500 keV, D0), both in Japan. Nevertheless, the system proposed for ITER represents a substantial technological challenge as an increase is required in beam energy, to 1 MeV, D0, accelerated ion (D-) current, to 40 A, accelerated current density, 200 A m-2 of D-, and pulse length, to 1 h. At the Fourth IAEA Technical Meeting on Negative Ion Based Neutral Beam Injectors, hosted by the Consorzio RFX, Padova, Italy, 9-11 May 2005, the status of the R&D aimed at the realization of the injectors for ITER was presented. Because of the importance of this development to the success of the ITER project, participants at that meeting were asked if they were interested in rewriting and extending their contributions as a submission to Nuclear Fusion. Technology papers were accepted because of the very nature of the subject. The submissions underwent the regular double-referee peer-review process
Beam overlapping in a multipass Ti:sapphire amplifier based on a parabolic mirror
Yang, Shengyi
2005-06-01
According to laser beam transporting in a multipass Ti:sapphire amplifier based on a parabolic mirror, the influential factors to induce astigmatism are analyzed. The beam waists of the laser beam transporting in the multipass amplifier are calculated by ABCD law in sagittal and tangential planes, respectively, and are compared with each other. Our analyses of these influential factors provide valuable data to optimize this design of multipass Ti:sapphire amplifier, and our experimental results of getting Gaussian beam from such a kind of amplifier confirmed our theoretical analyses.
Energy Technology Data Exchange (ETDEWEB)
Lin, X; Sun, T; Liu, T; Zhang, G; Yin, Y [Shandong Cancer Hospital, Jinan, Shandong (China)
2014-06-01
Purpose: To evaluate the dosimetric characteristics of intensity-modulated radiotherapy (IMRT) treatment plan with beam angle optimization. Methods: Ten post-operation patients with cervical cancer were included in this analysis. Two IMRT plans using seven beams were designed in each patient. A standard coplanar equi-space beam angles were used in the first plan (plan 1), whereas the selection of beam angle was optimized by beam angle optimization algorithm in Varian Eclipse treatment planning system for the same number of beams in the second plan (plan 2). Two plans were designed for each patient with the same dose-volume constraints and prescription dose. All plans were normalized to the mean dose to PTV. The dose distribution in the target, the dose to the organs at risk and total MU were compared. Results: For conformity and homogeneity in PTV, no statistically differences were observed in the two plans. For the mean dose in bladder, plan 2 were significantly lower than plan 1(p<0.05). No statistically significant differences were observed between two plans for the mean doses in rectum, left and right femur heads. Compared with plan1, the average monitor units reduced 16% in plan 2. Conclusion: The IMRT plan based on beam angle optimization for cervical cancer could reduce the dose delivered to bladder and also reduce MU. Therefore there were some dosimetric advantages in the IMRT plan with beam angle optimization for cervical cancer.
International Nuclear Information System (INIS)
Purpose: To evaluate the dosimetric characteristics of intensity-modulated radiotherapy (IMRT) treatment plan with beam angle optimization. Methods: Ten post-operation patients with cervical cancer were included in this analysis. Two IMRT plans using seven beams were designed in each patient. A standard coplanar equi-space beam angles were used in the first plan (plan 1), whereas the selection of beam angle was optimized by beam angle optimization algorithm in Varian Eclipse treatment planning system for the same number of beams in the second plan (plan 2). Two plans were designed for each patient with the same dose-volume constraints and prescription dose. All plans were normalized to the mean dose to PTV. The dose distribution in the target, the dose to the organs at risk and total MU were compared. Results: For conformity and homogeneity in PTV, no statistically differences were observed in the two plans. For the mean dose in bladder, plan 2 were significantly lower than plan 1(p<0.05). No statistically significant differences were observed between two plans for the mean doses in rectum, left and right femur heads. Compared with plan1, the average monitor units reduced 16% in plan 2. Conclusion: The IMRT plan based on beam angle optimization for cervical cancer could reduce the dose delivered to bladder and also reduce MU. Therefore there were some dosimetric advantages in the IMRT plan with beam angle optimization for cervical cancer
International Nuclear Information System (INIS)
Direct-aperture optimization (DAO) was applied to iterative beam-orientation selection in intensity-modulated radiation therapy (IMRT), so as to ensure a realistic segmental treatment plan at each iteration. Nested optimization engines dealt separately with gantry angles, couch angles, collimator angles, segment shapes, segment weights and wedge angles. Each optimization engine performed a random search with successively narrowing step sizes. For optimization of segment shapes, the filtered backprojection (FBP) method was first used to determine desired fluence, the fluence map was segmented, and then constrained direct-aperture optimization was used thereafter. Segment shapes were fully optimized when a beam angle was perturbed, and minimally re-optimized otherwise. The algorithm was compared with a previously reported method using FBP alone at each orientation iteration. An example case consisting of a cylindrical phantom with a hemi-annular planning target volume (PTV) showed that for three-field plans, the method performed better than when using FBP alone, but for five or more fields, neither method provided much benefit over equally spaced beams. For a prostate case, improved bladder sparing was achieved through the use of the new algorithm. A plan for partial scalp treatment showed slightly improved PTV coverage and lower irradiated volume of brain with the new method compared to FBP alone. It is concluded that, although the method is computationally intensive and not suitable for searching large unconstrained regions of beam space, it can be used effectively in conjunction with prior class solutions to provide individually optimized IMRT treatment plans
Beam optics optimization of a negative-ion sputter source
Indian Academy of Sciences (India)
F Osswald; R Rebmeister
2002-11-01
A negative-ion sputter source has been studied in order to increase the beam intensity delivered by the Vivitron tandem injector. The aim was to characterize the inﬂuence on the beam intensity of some factors related to the conﬁguration of the source such as the shape of the target holder, the target surface topography and the anode/cathode voltage. The paper reports the results carried out by experimentation on a test facility and on the injector itself as well as the investigations performed with computer simulations.
Beam optimization of helium injector for coupled RFQ–SFRFQ linac
International Nuclear Information System (INIS)
The coupled RFQ–SFRFQ (CRS) cavity designed in Peking University is a new type linac that coupled radio frequency quadrupole (RFQ) and separated function radio frequency quadrupole (SFRFQ) structure into a single cavity. An upgraded helium injector for the CRS cavity consisting of a 2.45 GHz permanent magnet electron cyclotron resonance (ECR) ion source and a 1.16 m low energy beam transport (LEBT) has been constructed and tested. The beam conditions of the injector were carefully optimized to satisfy the requirements of the CRS linac, the corresponding control system and a two-dimension scanner code CRSv1.0 were developed for optimizing the beam transmission from LEBT section to the entrance of the CRS cavity. The beam transmission efficiency has reached to approximately 87.5% as well as the optimized operating parameters were obtained by means of the scanner code
Correction of linear-array lidar intensity data using an optimal beam shaping approach
Xu, Fan; Wang, Yuanqing; Yang, Xingyu; Zhang, Bingqing; Li, Fenfang
2016-08-01
The linear-array lidar has been recently developed and applied for its superiority of vertically non-scanning, large field of view, high sensitivity and high precision. The beam shaper is the key component for the linear-array detection. However, the traditional beam shaping approaches can hardly satisfy our requirement for obtaining unbiased and complete backscattered intensity data. The required beam distribution should roughly be oblate U-shaped rather than Gaussian or uniform. Thus, an optimal beam shaping approach is proposed in this paper. By employing a pair of conical lenses and a cylindrical lens behind the beam expander, the expanded Gaussian laser was shaped to a line-shaped beam whose intensity distribution is more consistent with the required distribution. To provide a better fit to the requirement, off-axis method is adopted. The design of the optimal beam shaping module is mathematically explained and the experimental verification of the module performance is also presented in this paper. The experimental results indicate that the optimal beam shaping approach can effectively correct the intensity image and provide ~30% gain of detection area over traditional approach, thus improving the imaging quality of linear-array lidar.
Saada, Mohamed M.; Arafa, Mustafa H.; Nassef, Ashraf O.
2013-06-01
The use of vibration-based techniques in damage identification has recently received considerable attention in many engineering disciplines. While various damage indicators have been proposed in the literature, those relying only on changes in the natural frequencies are quite appealing since these quantities can conveniently be acquired. Nevertheless, the use of natural frequencies in damage identification is faced with many obstacles, including insensitivity and non-uniqueness issues. The aim of this article is to develop a viable damage identification scheme based only on changes in the natural frequencies and to attempt to overcome the challenges typically encountered. The proposed methodology relies on building a finite element model (FEM) of the structure under investigation. An improved particle swarm optimization algorithm is proposed to facilitate updating the FEM in accordance with experimentally determined natural frequencies in order to predict the damage location and extent. The method is tested on beam structures and was shown to be an effective tool for damage identification.
Reliability-Based Optimization in Structural Engineering
DEFF Research Database (Denmark)
Enevoldsen, I.; Sørensen, John Dalsgaard
1994-01-01
In this paper reliability-based optimization problems in structural engineering are formulated on the basis of the classical decision theory. Several formulations are presented: Reliability-based optimal design of structural systems with component or systems reliability constraints, reliability-b...
Application-Oriented Chemical Optimization of a Metakaolin Based Geopolymer
Directory of Open Access Journals (Sweden)
Raffaele Cioffi
2013-05-01
Full Text Available In this study the development of a metakaolin based geopolymeric mortar to be used as bonding matrix for external strengthening of reinforced concrete beams is reported. Four geopolymer formulations have been obtained by varying the composition of the activating solution in terms of SiO2/Na2O ratio. The obtained samples have been characterized from a structural, microstructural and mechanical point of view. The differences in structure and microstructure have been correlated to the mechanical properties. A major issue of drying shrinkage has been encountered in the high Si/Al ratio samples. In the light of the characterization results, the optimal geopolymer composition was then applied to fasten steel fibers to reinforced concrete beams. The mechanical behavior of the strengthened reinforced beams was evaluated by four-points bending tests, which were performed also on reinforced concrete beams as they are for comparison. The preliminary results of the bending tests point out an excellent behavior of the geopolymeric mixture tested, with the failure load of the reinforced beams roughly twice that of the control beam.
Qingyang Zhang; Guolin Yu; Hui Song
2015-01-01
Bird Mating Optimizer (BMO) is a novel meta-heuristic optimization algorithm inspired by intelligent mating behavior of birds. However, it is still insufficient in convergence of speed and quality of solution. To overcome these drawbacks, this paper proposes a hybrid algorithm (TLBMO), which is established by combining the advantages of Teaching-learning-based optimization (TLBO) and Bird Mating Optimizer (BMO). The performance of TLBMO is evaluated on 23 benchmark functions, and compared wit...
Xiangdong Qian; Maosen Cao; Zhongqing Su; Jiangang Chen
2012-01-01
Delamination is a type of representative damage in composite structures, severely degrading structural integrity and reliability. The identification of delamination is commonly treated as an issue of nondestructive testing. Differing from existing studies, a hybrid optimization algorithm (HOA), combining particle swarm optimization (PSO) with simplex method (SM), is proposed to identify delamination in laminated beams. The objective function of the optimization problem is created using delami...
Direct Optimization of Printed Reflectarrays for Contoured Beam Satellite Antenna Applications
DEFF Research Database (Denmark)
Zhou, Min; Sorensen, Stig B.; Kim, Oleksiy S.;
2013-01-01
, the geometrical parameters of the array elements are directly optimized to fulfill the contoured beam requirements, thus maintaining a direct relation between optimization goals and optimization variables, and hence resulting in more optimal designs. Both co- and cross-polar radiation patterns of the reflectarray...... that the designs obtained using the proposed direct optimization technique are superior in performance, both for multi-frequency and dual-polarization designs. A reflectarray breadboard has been manufactured and measured at the DTU-ESA Spherical Near-Field Antenna Test Facility to validate the proposed technique...
Application of Diamond Based Beam Loss Monitors
Hempel, Maria
2013-01-01
The LHC has an operational stored energy of 130MJ per beam. Only a small percentage of beam losses in the LHC equipment can damage material or lead to magnet quenches. Therefore, it is important to monitor different types of beam losses, e.g. scattering on residual gas particles, UFOs, collisions and injection losses. A detailed understanding of beam loss mechanisms is necessary to reduce them and ensure save operation. Two different beam loss monitors are installed in the LHC tunnel: ionizat...
Design and Optimization of Low Energy Beam Transport for TAC Proton Facility
Kisoglu, H F; Sultansoy, S; Yilmaz, M
2014-01-01
In this study, a low energy beam transport (LEBT) channel for the proton linac section of the Turkish Accelerator Center (TAC) has been designed by using TRAVEL code. Commonly used LEBT including two focusing solenoid magnets will transport and match the H- beam from a volume source to RFQ. In the beam dynamics simulations of such a LEBT line, 95% space-charge compensation (SCC) has been considered in this study. We aimed to find out the determination of our RFQ parameters that gives the best possible beam quality using beam collimator as an alternative way. In this way, we have acquired the best possible beam quality on RFQ input plane as well as optimizing the LEBT line.
GPU-Monte Carlo based fast IMRT plan optimization
Directory of Open Access Journals (Sweden)
Yongbao Li
2014-03-01
Full Text Available Purpose: Intensity-modulated radiation treatment (IMRT plan optimization needs pre-calculated beamlet dose distribution. Pencil-beam or superposition/convolution type algorithms are typically used because of high computation speed. However, inaccurate beamlet dose distributions, particularly in cases with high levels of inhomogeneity, may mislead optimization, hindering the resulting plan quality. It is desire to use Monte Carlo (MC methods for beamlet dose calculations. Yet, the long computational time from repeated dose calculations for a number of beamlets prevents this application. It is our objective to integrate a GPU-based MC dose engine in lung IMRT optimization using a novel two-steps workflow.Methods: A GPU-based MC code gDPM is used. Each particle is tagged with an index of a beamlet where the source particle is from. Deposit dose are stored separately for beamlets based on the index. Due to limited GPU memory size, a pyramid space is allocated for each beamlet, and dose outside the space is neglected. A two-steps optimization workflow is proposed for fast MC-based optimization. At first step, a rough dose calculation is conducted with only a few number of particle per beamlet. Plan optimization is followed to get an approximated fluence map. In the second step, more accurate beamlet doses are calculated, where sampled number of particles for a beamlet is proportional to the intensity determined previously. A second-round optimization is conducted, yielding the final result.Results: For a lung case with 5317 beamlets, 105 particles per beamlet in the first round, and 108 particles per beam in the second round are enough to get a good plan quality. The total simulation time is 96.4 sec.Conclusion: A fast GPU-based MC dose calculation method along with a novel two-step optimization workflow are developed. The high efficiency allows the use of MC for IMRT optimizations.--------------------------------Cite this article as: Li Y, Tian Z
Modeling and optimization of existing beam port facility of PSBR
International Nuclear Information System (INIS)
Due to inherited design issues with the current arrangement of beam ports (BPs) and reactor core-moderator assembly in The Perm State Breazeale Reactor (PSBR), the development of innovative experimental facilities utilizing neutron beams is extremely limited. Therefore, a study has started to examine the existing BPs for neutron and gamma outputs and develop a new core-moderator location and BP geometry in PSBR. Although 7 BPs are placed in PSBR, 2 of them are using currently. In this study BP 4, one of the currently being used BP, is examined. With changing the location of the BP 4 and structure of the core assembly, some artificial models are developed and compared with the original model
Lefaudeux, Nicolas; Levecq, Xavier; Dovillaire, Guillaume; Theis, Sebastien; Escolano, Lionnel
2012-02-01
When ultra high intensity lasers facilities were in their early development, the only concern was getting laser pulses with the right energy and pulse duration. As facilities are orienting toward the end users, they are now required to deliver a laser beam with additional qualities like a focal spot with constant quality. That is why Adaptive Optics is now a standard feature for the current ultra high intensity lasers facilities to correct for the aberrations of the beam exiting the laser chain. However, the very last optical components, like the off axis parabola to focus the beam induce aberrations that cannot be directly corrected as they are located after the wavefront sensing. We present a new technology of deformable mirror and a new correction strategy to get optimal focal spot in the experiment chamber as well as measurement of the actual beam quality in the chamber while the beam is used for experiments. These deformable mirrors were designed taking into account needs of ultra intense laser applications. They provide exceptional stability, optical quality and innovative features like scalability and maintenance of the reflective surface. The method of correction proposed uses usual adaptive optics loop to correct for all the aberration from the laser chain, as well as additional steps to get an optimal focal spot in the experiment chamber on a non amplified beam, and to correct and measure the actual beam quality on the amplified beam while it is used for experiments.
International Nuclear Information System (INIS)
An important element of radiation treatment planning for cancer therapy is the selection of beam angles (out of all possible coplanar and non-coplanar angles in relation to the patient) in order to maximize the delivery of radiation to the tumor site and minimize radiation damage to nearby organs-at-risk. This category of combinatorial optimization problem is particularly difficult because direct evaluation of the quality of treatment corresponding to any proposed selection of beams requires the solution of a large-scale dose optimization problem involving many thousands of variables that represent doses delivered to volume elements (voxels) in the patient. However, if the quality of angle sets can be accurately estimated without expensive computation, a large number of angle sets can be considered, increasing the likelihood of identifying a very high quality set. Using a computationally efficient surrogate beam set evaluation procedure based on single-beam data extracted from plans employing equally-spaced beams (eplans), we have developed a global search metaheuristic process based on the nested partitions framework for this combinatorial optimization problem. The surrogate scoring mechanism allows us to assess thousands of beam set samples within a clinically acceptable time frame. Tests on difficult clinical cases demonstrate that the beam sets obtained via our method are of superior quality. (paper)
Indian Academy of Sciences (India)
V C Petwal; V K Senecha; K V Subbaiah; H C Soni; S Kotaiah
2007-02-01
Monte Carlo calculations have been performed using MCNP code to study the optimization of photo-neutron yield for different electron beam energies impinging on Pb, W and Ta cylindrical targets of varying thickness. It is noticed that photo-neutron yield can be increased for electron beam energies ≥ 100 MeV for appropriate thickness of the target. It is also noticed that it can be maximized by further increasing the thickness of the target. Further, at higher electron beam energy heat gradient in the target decreases, which facilitates easier heat removal from the target. This can help in developing a photo-neutron source based on electron LINAC by choosing appropriate electron beam energy and target thickness to optimize the neutron flux for ADS, transmutation studies and as high energy neutron source etc. Photo-neutron yield for different targets, optimum target thickness and photo-neutron energy spectrum and heat deposition by electron beam for different incident energy is presented.
Classifiers based on optimal decision rules
Amin, Talha
2013-11-25
Based on dynamic programming approach we design algorithms for sequential optimization of exact and approximate decision rules relative to the length and coverage [3, 4]. In this paper, we use optimal rules to construct classifiers, and study two questions: (i) which rules are better from the point of view of classification-exact or approximate; and (ii) which order of optimization gives better results of classifier work: length, length+coverage, coverage, or coverage+length. Experimental results show that, on average, classifiers based on exact rules are better than classifiers based on approximate rules, and sequential optimization (length+coverage or coverage+length) is better than the ordinary optimization (length or coverage).
A microwave chip-based beam splitter for low-energy guided electrons
Hammer, J; Weber, Ph; Hommelhoff, P
2014-01-01
We demonstrate the splitting of a low-energy electron beam by means of a microwave pseudopotential formed above a planar chip substrate. Beam splitting arises from smoothly transforming the transverse guiding potential for an electron beam from a single-well harmonic confinement into a double-well, thereby generating two separated output beams with $5\\,$mm lateral spacing. Efficient beam splitting is observed for electron kinetic energies up to $3\\,$eV, in excellent agreement with particle tracking simulations. Furthermore, we present a beam splitter potential that is numerically optimized towards coherent and adiabatic splitting of guided electron wave packets. Prospects for electron-based quantum matter-wave optics applications are discussed.
Elsied, Ahmed M M; Li, Song; Mirzaie, Mohammad; Sokollik, Thomas; Zhang, Jie
2014-01-01
At Shanghai Jiao Tong University, we have established a research laboratory for advanced acceleration research based on high-power lasers and plasma technologies. In a primary experiment based on the laser wakefield acceleration (LWFA) scheme, multi-hundred MeV electron beams having a reasonable quality are generated using 20-40 TW, 30 femtosecond laser pulses interacting independently with helium, neon, nitrogen and argon gas jet targets. The laser-plasma interaction conditions are optimized for stabilizing the electron beam generation from each type of gas. The electron beam pointing angle stability and divergence angle as well as the energy spectra from each gas jet are measured and compared.
Demonstration of Cathode Emittance Dominated High Bunch Charge Beams in a DC gun-based Photoinjector
Gulliford, Colwyn; Bazarov, Ivan; Dunham, Bruce; Cultrera, Luca
2015-01-01
We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (greater than or equal to 100 pC) beams produced in the DC gun-based Cornell Energy Recovery Linac Photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittance measured at 9-9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs (ERLs) and Free Electron Lasers (FELs).
Demonstration of cathode emittance dominated high bunch charge beams in a DC gun-based photoinjector
International Nuclear Information System (INIS)
We present the results of transverse emittance and longitudinal current profile measurements of high bunch charge (≥100 pC) beams produced in the DC gun-based Cornell energy recovery linac photoinjector. In particular, we show that the cathode thermal and core beam emittances dominate the final 95% and core emittances measured at 9–9.5 MeV. Additionally, we demonstrate excellent agreement between optimized 3D space charge simulations and measurement, and show that the quality of the transverse laser distribution limits the optimal simulated and measured emittances. These results, previously thought achievable only with RF guns, demonstrate that DC gun based photoinjectors are capable of delivering beams with sufficient single bunch charge and beam quality suitable for many current and next generation accelerator projects such as Energy Recovery Linacs and Free Electron Lasers
A nested partitions framework for beam angle optimization in intensity-modulated radiation therapy
International Nuclear Information System (INIS)
Coupling beam angle optimization with dose optimization in intensity-modulated radiation therapy (IMRT) increases the size and complexity of an already large-scale combinatorial optimization problem. We have developed a novel algorithm, nested partitions (NP), that is capable of finding suitable beam angle sets by guiding the dose optimization process. NP is a metaheuristic that is flexible enough to guide the search of a heuristic or deterministic dose optimization algorithm. The NP method adaptively samples from the entire feasible region, or search space, and coordinates the sampling effort with a systematic partitioning of the feasible region at successive iterations, concentrating the search in promising subsets. We used a 'warm-start' approach by initiating NP with beam angle samples derived from an integer programming (IP) model. In this study, we describe our implementation of the NP framework with a commercial optimization algorithm. We compared the NP framework with equi-spaced beam angle selection, the IP method, greedy heuristic and random sampling heuristic methods. The results of the NP approach were evaluated using two clinical cases (head and neck and whole pelvis) involving the primary tumor and nodal volumes. Our results show that NP produces better quality solutions than the alternative considered methods
A nested partitions framework for beam angle optimization in intensity-modulated radiation therapy
D'Souza, Warren D.; Zhang, Hao H.; Nazareth, Daryl P.; Shi, Leyuan; Meyer, Robert R.
2008-06-01
Coupling beam angle optimization with dose optimization in intensity-modulated radiation therapy (IMRT) increases the size and complexity of an already large-scale combinatorial optimization problem. We have developed a novel algorithm, nested partitions (NP), that is capable of finding suitable beam angle sets by guiding the dose optimization process. NP is a metaheuristic that is flexible enough to guide the search of a heuristic or deterministic dose optimization algorithm. The NP method adaptively samples from the entire feasible region, or search space, and coordinates the sampling effort with a systematic partitioning of the feasible region at successive iterations, concentrating the search in promising subsets. We used a 'warm-start' approach by initiating NP with beam angle samples derived from an integer programming (IP) model. In this study, we describe our implementation of the NP framework with a commercial optimization algorithm. We compared the NP framework with equi-spaced beam angle selection, the IP method, greedy heuristic and random sampling heuristic methods. The results of the NP approach were evaluated using two clinical cases (head and neck and whole pelvis) involving the primary tumor and nodal volumes. Our results show that NP produces better quality solutions than the alternative considered methods.
Optimization of a neutrino beam for the study of CP violation with the LENA detector
International Nuclear Information System (INIS)
Neutrino beams are nowadays a commonly used and well investigated tool to study neutrino oscillations, e.g. T2K, NOνA experiments. Beam neutrinos are produced by the decays of properly focused particles, mostly pions and kaons, generated by the collisions of accelerated protons with a target. The shape and composition of the obtained neutrino fluxes depend on the properties of the neutrino production apparatus. Primary beam, target, focusing system, decay tunnel must be optimized relatively to the neutrino detector, in order to achieve the highest possible sensitivity to oscillation parameters such as the CP-violating phase δcp. This talk will focus on the optimization of a neutrino beam from the European Spallation Source (ESS) in Lund, Sweden, to the liquid scintillator neutrino detector LENA, proposed in the Pyhaesalmi mine in Finland.
Optimization of a neutrino beam for the study of CP violation with the LENA detector
Energy Technology Data Exchange (ETDEWEB)
Genster, Christoph; Meloni, Marta; Soiron, Michael; Stahl, Achim; Weifels, Marcel; Wiebusch, Christopher [RWTH Aachen University, III. Physikalisches Institut B (Germany)
2015-07-01
Neutrino beams are nowadays a commonly used and well investigated tool to study neutrino oscillations, e.g. T2K, NOνA experiments. Beam neutrinos are produced by the decays of properly focused particles, mostly pions and kaons, generated by the collisions of accelerated protons with a target. The shape and composition of the obtained neutrino fluxes depend on the properties of the neutrino production apparatus. Primary beam, target, focusing system, decay tunnel must be optimized relatively to the neutrino detector, in order to achieve the highest possible sensitivity to oscillation parameters such as the CP-violating phase δ{sub cp}. This talk will focus on the optimization of a neutrino beam from the European Spallation Source (ESS) in Lund, Sweden, to the liquid scintillator neutrino detector LENA, proposed in the Pyhaesalmi mine in Finland.
Application of diamond based beam loss monitors
International Nuclear Information System (INIS)
The LHC has an operational stored energy of 130MJ per beam. Only a small percentage of beam losses in the LHC equipment can damage material or lead to magnet quenches. Therefore, it is important to monitor different types of beam losses, e.g. scattering on residual gas particles, UFOs, collisions and injection losses. A detailed understanding of beam loss mechanisms is necessary to reduce them and ensure save operation. Two different beam loss monitors are installed in the LHC tunnel: ionization chambers and diamond sensors. Ionization chambers trigger a beam dump if beam losses exceed a certain threshold. They have a time resolution of 40um (half LHC turn) which is not sufficient to resolve bunch-by-bunch beam losses. Diamond sensors have a nanosecond time resolution and can therefore detect bunch-by-bunch beam losses. This time resolution allows an analysis of various types of beam losses and an understanding of the mechanisms. For the first time beam loss intensities were measured bunch-by-bunch caused by different origins of losses. Beam loss measurements using diamond sensors will be presented. The results are compared to simulations and good qualitative agreement was found. The potential of diamond sensors for LHC and experiment applications are discussed.
Application of diamond based beam loss monitors
Energy Technology Data Exchange (ETDEWEB)
Hempel, Maria [Brandenburgische Technische Univ. Cottbus (Germany); DESY, Zeuthen (Germany); CERN, Geneva (Switzerland); Baer, Tobias [CERN, Geneva (Switzerland); Hamburg Univ. (Germany); Castro Carballo, Elena Maria [DESY, Zeuthen (Germany); Lohmann, Wolfgang [Brandenburgische Technische Univ. Cottbus (Germany); DESY, Zeuthen (Germany); Schmidt, Ruediger [CERN, Geneva (Switzerland)
2013-07-01
The LHC has an operational stored energy of 130MJ per beam. Only a small percentage of beam losses in the LHC equipment can damage material or lead to magnet quenches. Therefore, it is important to monitor different types of beam losses, e.g. scattering on residual gas particles, UFOs, collisions and injection losses. A detailed understanding of beam loss mechanisms is necessary to reduce them and ensure save operation. Two different beam loss monitors are installed in the LHC tunnel: ionization chambers and diamond sensors. Ionization chambers trigger a beam dump if beam losses exceed a certain threshold. They have a time resolution of 40um (half LHC turn) which is not sufficient to resolve bunch-by-bunch beam losses. Diamond sensors have a nanosecond time resolution and can therefore detect bunch-by-bunch beam losses. This time resolution allows an analysis of various types of beam losses and an understanding of the mechanisms. For the first time beam loss intensities were measured bunch-by-bunch caused by different origins of losses. Beam loss measurements using diamond sensors will be presented. The results are compared to simulations and good qualitative agreement was found. The potential of diamond sensors for LHC and experiment applications are discussed.
Hybrid Biogeography Based Optimization for Constrained Numerical and Engineering Optimization
Directory of Open Access Journals (Sweden)
Zengqiang Mi
2015-01-01
Full Text Available Biogeography based optimization (BBO is a new competitive population-based algorithm inspired by biogeography. It simulates the migration of species in nature to share information. A new hybrid BBO (HBBO is presented in the paper for constrained optimization. By combining differential evolution (DE mutation operator with simulated binary crosser (SBX of genetic algorithms (GAs reasonably, a new mutation operator is proposed to generate promising solution instead of the random mutation in basic BBO. In addition, DE mutation is still integrated to update one half of population to further lead the evolution towards the global optimum and the chaotic search is introduced to improve the diversity of population. HBBO is tested on twelve benchmark functions and four engineering optimization problems. Experimental results demonstrate that HBBO is effective and efficient for constrained optimization and in contrast with other state-of-the-art evolutionary algorithms (EAs, the performance of HBBO is better, or at least comparable in terms of the quality of the final solutions and computational cost. Furthermore, the influence of the maximum mutation rate is also investigated.
A test beam upgrade based on the BEPC-LINAC
International Nuclear Information System (INIS)
A total of three beam lines, E1, E2 and E3 have based on the LINAC of BEPC. The E1 beam is to be used for intense slow-positron facility. The E2 is a primary positron or electron beam with an energy of 1.3-1.5 GeV. The E3 is a secondary electron or pion test beam with a momentum can be adjustable continuously. The position accuracy of a detected particle is 0.2-0.4 mm with an event rate of 3 - 4 Hz. This beam has been successfully used for some detectors beam test. (author)
Optimal Truncation of Element Beam in a Coherent Fiber Laser Array
Institute of Scientific and Technical Information of China (English)
ZHOU Pu; WANG Xiao-Lin; MA Yan-Xing; MA Hao-Tong; LIU Ze-Jin; XU Xiao-Jun
2009-01-01
@@ The beam quality of a coherent fber laser array often suffers from the low fill factor of the Gaussian laser array. One simple and effective approach to improve the fill factor is to truncate the array element properly. An analytical expression for far-field intensity distribution of a truncated coherent fiber laser array is derived. Optimal truncation of the element beam in different coherent fiber laser arrays is obtained by using energy encircled in the far-fieM central-lobe as the beam quality criterion. By optimal truncation, energy encircled in the central-lobe can be 97% compared with the ideal case. The shift in optimal truncation parameter in the case of phase noise is also analyzed.
Wilder, Benjamin A.
2010-01-01
When compared to other laser types, the Free Electron Laser (FEL) provides optimal beam quality for successful atmospheric propagation. Assuming the development and deployment of a mega-watt (MW) class, ground or sea based FEL, this thesis investigates several proposed space applications including power beaming to satellites, the removal of orbital debris, laser illumination of objects within the solar system for scientific study, and interstellar laser illumination for communications. Po...
Machine specific fracture optimization for JEOL e-beam mask writer
Yeap, Johnny; Kondepudy, Raghava; Kulkarni, Parikshit; Kawase, Yuichi; Cinque, Russell
2010-05-01
Traditionally, Mask Data Preparation (MDP) flow for Variable Shape E-Beam (VSB) writers has been optimized in a generic fashion to minimize slivers and reduce shot count while maintaining data symmetry. To date, this approach has been sufficient and allowed the mask industry to meet requirements for CD uniformity, registration, and write time. However, ever tighter error budgets and increasing pattern complexity are driving a need for writer-specific optimization of MDP. This paper summarizes the joint development effort between Synopsys and JEOL to optimize MDP fractures for the JEOL platform. The advantages and challenges of platform specific optimization are discussed.
基于数值仿真的波形护栏防阻块优化设计%Optimal Design of W-Beam Blocks Based on Numerical Simulation
Institute of Scientific and Technical Information of China (English)
吴中; 施金金
2012-01-01
Based on Mechanical analysis of Blocks,the main factors to improve energy absorption and the stumbling prevention ability are deternined, and a design is proposed to optimize the Hexagon blocks for decagonal blocks. Ls-Dyna crash analysis of the blocks finds out that the crash performance of optimal blocks is greatly improved. By the numerical crash experiment of a real car,the stumbling effect of the column is smaller due to stronger deformation resistance of the optimal blocks and the improved energy absorption and guiding abilities.%对防阻块的碰撞性能进行了力学分析,找出了改善防阻块吸能效果及防绊阻能力的主要因素,提出将六边形防阻块优化为十边形防阻块的设计方案.使用LS-DYNA在不同撞击程度下,对防阻块进行碰撞分析,发现优化防阻块的碰撞性能有较大提升.通过实车碰撞数值实验得出,由于优化防阻块抗变形能力得到提升,因而减小了立柱对车辆前轮的绊阻效应,增强了整体护栏结构的吸能导向作用
Directory of Open Access Journals (Sweden)
Qingyang Zhang
2015-02-01
Full Text Available Bird Mating Optimizer (BMO is a novel meta-heuristic optimization algorithm inspired by intelligent mating behavior of birds. However, it is still insufficient in convergence of speed and quality of solution. To overcome these drawbacks, this paper proposes a hybrid algorithm (TLBMO, which is established by combining the advantages of Teaching-learning-based optimization (TLBO and Bird Mating Optimizer (BMO. The performance of TLBMO is evaluated on 23 benchmark functions, and compared with seven state-of-the-art approaches, namely BMO, TLBO, Artificial Bee Bolony (ABC, Particle Swarm Optimization (PSO, Fast Evolution Programming (FEP, Differential Evolution (DE, Group Search Optimization (GSO. Experimental results indicate that the proposed method performs better than other existing algorithms for global numerical optimization.
STED microscopy based on axially symmetric polarized vortex beams
Zhehai, Zhou; Lianqing, Zhu
2016-03-01
A stimulated emission depletion (STED) microscopy scheme using axially symmetric polarized vortex beams is proposed based on unique focusing properties of such kinds of beams. The concept of axially symmetric polarized vortex beams is first introduced, and the basic principle about the scheme is described. Simulation results for several typical beams are then shown, including radially polarized vortex beams, azimuthally polarized vortex beams, and high-order axially symmetric polarized vortex beams. The results indicate that sharper doughnut spots and thus higher resolutions can be achieved, showing more flexibility than previous schemes based on flexible modulation of both phase and polarization for incident beams. Project supported by the National Natural Science Foundation of China (Grant Nos. 61108047 and 61475021), the Natural Science Foundation of Beijing, China (Grant No. 4152015), the Program for New Century Excellent Talents in Universities of China (Grant No. NCET-13-0667), and the Top Young Talents Support Program of Beijing, China (Grant No. CIT&TCD201404113).
Numerical optimization approaches of single-pulse conduction laser welding by beam shape tailoring
Sundqvist, J.; Kaplan, A. F. H.; Shachaf, L.; Brodsky, A.; Kong, C.; Blackburn, J.; Assuncao, E.; Quintino, L.
2016-04-01
While circular laser beams are usually applied in laser welding, for certain applications tailoring of the laser beam shape, e.g. by diffractive optical elements, can optimize the process. A case where overlap conduction mode welding should be used to produce a C-shaped joint was studied. For the dimensions studied in this paper, the weld joint deviated significantly from the C-shape of the single-pulse laser beam. Because of the complex heat flow interactions, the process requires optimization. Three approaches for extracting quantitative indicators for understanding the essential heat flow contributions process and for optimizing the C-shape of the weld and of the laser beam were studied and compared. While integral energy properties through a control volume and temperature gradients at key locations only partially describe the heat flow behaviour, the geometrical properties of the melt pool isotherm proved to be the most reliable method for optimization. While pronouncing the C-ends was not sufficient, an additional enlargement of the laser beam produced the desired C-shaped weld joint. The approach is analysed and the potential for generalization is discussed.
Energy Technology Data Exchange (ETDEWEB)
Zhou, F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Bohler, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ding, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gilevich, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ratner, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Vetter, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States)
2015-12-07
Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Light Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.
Laser fusion target illumination optimization with consideration of the beam divergence
International Nuclear Information System (INIS)
Using a focusing system with a great focal length it is demonstrated that the radiation divergence considerably influences the illumination optimization. If the channel beam is composed of several single beams, there are two optimum illumination variants: the channel beam tangent and the single beam tangent illumination. Further, it is shown that the illumination channel distribution function can vary in the central region without any effect on the illumination uniformity. The deviation at the periphery is more critical. The most homogeneous illumination and favourable energy transfer would be obtained by low radiation divergence and optimum lateral and axial defocusing of the single beam imaging a suitable near-field intensity pattern on the target surface. It is emphasized that the estimation was made without considering the plasma parameters and the dynamic variation in time. (author)
Optimal tracking control of a flexible hub-beam system with time delay
International Nuclear Information System (INIS)
In this paper, a new technique of time-delay compensation is proposed for active control of a flexible hub-beam system. The first-order approximation coupling (FOAC) model proposed recently for dynamics of hub-beam systems is used to verify the applicability of this technique. The FOAC model is first linearized to obtain a linearized equation. The linearized equation with time delay is then transformed into a standard form with no time delay by a particular integral transformation. The time-delay controller is designed based on this standard equation using the classical optimal tracking control theory. Since the controller is a function of modal coordinates, a modal filter is presented to estimate the modal coordinates from physical sensor measurements. The effectiveness of the proposed technique for time delay is demonstrated by numerical simulations. Simulation results indicate that a very small time delay may result in instability of the control system if it is not compensated in control design. The proposed time-delay controller is effective in controlling the system even when the maximum time delay for stability without time-delay compensation is greatly exceeded. Moreover, for the system without time delay, the proposed time-delay controller may possibly obtain much better control effectiveness than the controller without time delay
Cantilever-Based Microwave Biosensors: Analysis, Designs and Optimizations
DEFF Research Database (Denmark)
Jiang, Chenhui; Johansen, Tom Keinicke; Jónasson, Sævar Þór;
2011-01-01
resonators is at first theoretically analyzed. A LC resonator based biosensor with beams is designed and optimized by using 3D electromagnetic (EM) simulations, where the beam is a typical variation of cantilevers. The sensitivity of the lossless biosensor is predicted as 4.6MHz/nm. The 3-dB bandwidths of......This paper presents a novel microwave readout scheme for measuring deflection of cantilevers in nanometer range. The cantilever deflection can be sensed by the variation of transmission levels or resonant frequencies of microwave signals. The sensitivity of the cantilever biosensor based on LC...... the resonances are narrowed for improving the resolution of distinguishing resonances by reducing conductive loss of electrodes. The lossy biosensor can achieve the highest sensitivity as 5.6 MHz/nm and narrowest 3-dB bandwidth as 5 GHz....
Optimal focusing conditions of lenses using Gaussian beams
Franco, Juan Manuel; Cywiak, Moisés; Cywiak, David; Mourad, Idir
2016-07-01
By using the analytical equations of the propagation of Gaussian beams in which truncation exhibits negligible consequences, we describe a method that uses the value of the focal length of a focusing lens to classify its focusing performance. We show that for different distances between a laser and a focusing lens there are different planes where best focusing conditions can be obtained and we demonstrate how the value of the focal length impacts the lens focusing properties. To perform the classification we introduce the term delimiting focal length. As the value of the focal length used in wave propagation theory is nominal and difficult to measure accurately, we describe an experimental approach to calculate its value matching our analytical description. Finally, we describe possible applications of the results for characterizing Gaussian sources, for measuring focal lengths and/or alternatively for characterizing piston-like movements.
Risk based surveillance test interval optimization
International Nuclear Information System (INIS)
First step towards the risk based regulation is to determine the optimal surveillance test intervals for the safety equipment which is tested at nuclear power plant operation. In the paper we have presented the process of optimal surveillance test interval optimization from our perspective. It consist of three levels: component level, system level and plant level. It bases on the results of the Probabilistic Safety Assessment and is focused to minimize risk. At component and system level the risk measure is component or system mean unavailability respectively. At plant level the risk measure is core damage frequency. (author)
Brugger, Markus; Assmann, R W; Forkel-Wirth, Doris; Menzel, Hans Gregor; Roesler, Stefan; Vincke, Helmut H
2005-01-01
Radiation protection of the personnel who will perform interventions in the LHC Beam Cleaning Insertions is mandatory and includes the design of equipment and the establishment of work procedures. Residual dose rates due to activated equipment are expected to reach significant values such that any maintenance has to be planned and optimized in advance. Three-dimensional maps of dose equivalent rates at different cooling times after operation of the LHC have been calculated with FLUKA. The simulations are based on an explicit calculation of induced radioactivity and of the transport of the radiation from the radioactive decay. The paper summarizes the results for the Beam Cleaning Insertions and discusses the estimation of individual and collective doses received by personnel during critical interventions, such as the exchange of a collimator or the installation of Phase 2. The given examples outline the potential and the need to optimize, in an iterative way, the design of components as well as the layout of ...
Nanodosimetry-Based Plan Optimization for Particle Therapy.
Casiraghi, Margherita; Schulte, Reinhard W
2015-01-01
Treatment planning for particle therapy is currently an active field of research due uncertainty in how to modify physical dose in order to create a uniform biological dose response in the target. A novel treatment plan optimization strategy based on measurable nanodosimetric quantities rather than biophysical models is proposed in this work. Simplified proton and carbon treatment plans were simulated in a water phantom to investigate the optimization feasibility. Track structures of the mixed radiation field produced at different depths in the target volume were simulated with Geant4-DNA and nanodosimetric descriptors were calculated. The fluences of the treatment field pencil beams were optimized in order to create a mixed field with equal nanodosimetric descriptors at each of the multiple positions in spread-out particle Bragg peaks. For both proton and carbon ion plans, a uniform spatial distribution of nanodosimetric descriptors could be obtained by optimizing opposing-field but not single-field plans. The results obtained indicate that uniform nanodosimetrically weighted plans, which may also be radiobiologically uniform, can be obtained with this approach. Future investigations need to demonstrate that this approach is also feasible for more complicated beam arrangements and that it leads to biologically uniform response in tumor cells and tissues. PMID:26167202
Nanodosimetry-Based Plan Optimization for Particle Therapy
Directory of Open Access Journals (Sweden)
Margherita Casiraghi
2015-01-01
Full Text Available Treatment planning for particle therapy is currently an active field of research due uncertainty in how to modify physical dose in order to create a uniform biological dose response in the target. A novel treatment plan optimization strategy based on measurable nanodosimetric quantities rather than biophysical models is proposed in this work. Simplified proton and carbon treatment plans were simulated in a water phantom to investigate the optimization feasibility. Track structures of the mixed radiation field produced at different depths in the target volume were simulated with Geant4-DNA and nanodosimetric descriptors were calculated. The fluences of the treatment field pencil beams were optimized in order to create a mixed field with equal nanodosimetric descriptors at each of the multiple positions in spread-out particle Bragg peaks. For both proton and carbon ion plans, a uniform spatial distribution of nanodosimetric descriptors could be obtained by optimizing opposing-field but not single-field plans. The results obtained indicate that uniform nanodosimetrically weighted plans, which may also be radiobiologically uniform, can be obtained with this approach. Future investigations need to demonstrate that this approach is also feasible for more complicated beam arrangements and that it leads to biologically uniform response in tumor cells and tissues.
Genetic algorithm based separation cascade optimization
International Nuclear Information System (INIS)
The conventional separation cascade design procedure does not give an optimum design because of squaring-off, variation of flow rates and separation factor of the element with respect to stage location. Multi-component isotope separation further complicates the design procedure. Cascade design can be stated as a constrained multi-objective optimization. Cascade's expectation from the separating element is multi-objective i.e. overall separation factor, cut, optimum feed and separative power. Decision maker may aspire for more comprehensive multi-objective goals where optimization of cascade is coupled with the exploration of separating element optimization vector space. In real life there are many issues which make it important to understand the decision maker's perception of cost-quality-speed trade-off and consistency of preferences. Genetic algorithm (GA) is one such evolutionary technique that can be used for cascade design optimization. This paper addresses various issues involved in the GA based multi-objective optimization of the separation cascade. Reference point based optimization methodology with GA based Pareto optimality concept for separation cascade was found pragmatic and promising. This method should be explored, tested, examined and further developed for binary as well as multi-component separations. (author)
A Monte Carlo-based treatment-planning tool for ion beam therapy
Böhlen, T T; Dosanjh, M; Ferrari, A; Haberer, T; Parodi, K; Patera, V; Mairan, A
2013-01-01
Ion beam therapy, as an emerging radiation therapy modality, requires continuous efforts to develop and improve tools for patient treatment planning (TP) and research applications. Dose and fluence computation algorithms using the Monte Carlo (MC) technique have served for decades as reference tools for accurate dose computations for radiotherapy. In this work, a novel MC-based treatment-planning (MCTP) tool for ion beam therapy using the pencil beam scanning technique is presented. It allows single-field and simultaneous multiple-fields optimization for realistic patient treatment conditions and for dosimetric quality assurance for irradiation conditions at state-of-the-art ion beam therapy facilities. It employs iterative procedures that allow for the optimization of absorbed dose and relative biological effectiveness (RBE)-weighted dose using radiobiological input tables generated by external RBE models. Using a re-implementation of the local effect model (LEM), theMCTP tool is able to perform TP studies u...
Modeling and simulation of LHC beam-based collimator setup
Valentino, G; Assmann, R W; Burkart, F; Redaelli, S; Rossi, A; Lari, L
2012-01-01
In the 2011 Large Hadron Collider run, collimators were aligned for proton and heavy ion beams using a semiautomatic setup algorithm. The algorithm provided a reduction in the beam time required for setup, an elimination of beam dumps during setup and better reproducibility with respect to manual alignment. A collimator setup simulator was developed based on a Gaussian model of the beam distribution as well as a parametric model of the beam losses. A time-varying beam loss signal can be simulated for a given collimator movement into the beam. The simulation results and comparison to measurement data obtained during collimator setups and dedicated fills for beam halo scraping are presented. The simulator will then be used to develop a fully automatic collimator alignment algorithm.
Optimization of multi-constrained structures based on optimality criteria
Rizzi, P.
1976-01-01
A weight-reduction algorithm is developed for the optimal design of structures subject to several multibehavioral inequality constraints. The structural weight is considered to depend linearly on the design variables. The algorithm incorporates a simple recursion formula derived from the Kuhn-Tucker necessary conditions for optimality, associated with a procedure to delete nonactive constraints based on the Gauss-Seidel iterative method for linear systems. A number of example problems is studied, including typical truss structures and simplified wings subject to static loads and with constraints imposed on stresses and displacements. For one of the latter structures, constraints on the fundamental natural frequency and flutter speed are also imposed. The results obtained show that the method is fast, efficient, and general when compared to other competing techniques. Extensions to the generality of the method to include equality constraints and nonlinear merit functions is discussed.
Optimizing 50kV hydrogen diagnostic neutral beam performance for active spectroscopy in MST
Feng, X.; Boguski, J.; Craig, D.; den Hartog, D. J.; Munaretto, S.; Nornberg, M. D.; Olivia, S.
2015-11-01
The 50 kV hydrogen diagnostic neutral beam on MST provides local measurements of impurity ion emission through charge exchange recombination spectroscopy (CHERS) and of core-localized magnetic field through the motional Stark effect (MSE). The beam, which was designed to provide 5A of neutral current at 50 kV to meet these needs, is currently on a test stand to accommodate diagnosis, in order to increase the reliability of beam formation, sustain a steady current of 5 amps for 20ms, and optimize the primary energy fraction. The reliability of arc formation was increased from 40% to 80% success rate with increase of cathode gas pressure from 150kPa to 200kPa, and the stability of the arc current is improved with a decrease of the insulation magnetic field. A calorimeter with 5 thermocouples is installed to measure the horizontal and vertical beam profiles as well as beam divergence. Beam energy components are quantified through Doppler-shift spectroscopy. Preliminary simulation results of the beam using the ALCBEAM code as well as a description of how changes to the beam performance can affect CHERS and MSE measurements are presented. This work is supported by the U.S. DOE.
Augusta Neto, Maria; Yu, Wenbin; Pereira Leal, Rogerio
2008-10-01
This article describes a new approach to design the cross-section layer orientations of composite laminated beam structures. The beams are modelled with realistic cross-sectional geometry and material properties instead of a simplified model. The VABS (the variational asymptotic beam section analysis) methodology is used to compute the cross-sectional model for a generalized Timoshenko model, which was embedded in the finite element solver FEAP. Optimal design is performed with respect to the layers' orientation. The design sensitivity analysis is analytically formulated and implemented. The direct differentiation method is used to evaluate the response sensitivities with respect to the design variables. Thus, the design sensitivities of the Timoshenko stiffness computed by VABS methodology are imbedded into the modified VABS program and linked to the beam finite element solver. The modified method of feasible directions and sequential quadratic programming algorithms are used to seek the optimal continuous solution of a set of numerical examples. The buckling load associated with the twist-bend instability of cantilever composite beams, which may have several cross-section geometries, is improved in the optimization procedure.
A steering magnet optimized by random search method for high current beam transport line
International Nuclear Information System (INIS)
We present an improved design of the steering magnet which produces almost uniform magnetic field in the region through which beam passes. Optimization of the parameters of the steering magnet is done by random search method. It is shown that use of a suitable shim reduces the field deviation by a great extent. (author)
Optimization of Beam Properties with Respect to Maximum Band-Gap
DEFF Research Database (Denmark)
Halkjær, Søren; Sigmund, Ole
2004-01-01
We study numerically the frequency band-gap phenomenon for bending waves in an infinite periodic beam. The outcome of the analysis is then subjected to an optimization problem in order to maximize these band-gaps. The band-gap maximization may be performed with respect to material parameters and...
Optimization for manufacturing system based on Pheromone
Directory of Open Access Journals (Sweden)
Lei Wang
2011-06-01
Full Text Available A new optimization approach, called pheromone, which comes from the collective behavior of ant colonies for food foraging is proposed to optimize task allocation. These ants spread pheromone information and make global information available locally; thus, an ant agent only needs to observe its local environment in order to account for nonlocal concerns in its decisions. This approach has the capacity for task allocation model to automatically find efficient routing paths for processing orders and to reduce communication overhead, which exists in contract net protocol, in shop floor control system. An example confirms that a pheromone-based optimization approach has an excellent allocation performance in shop floor.
Beam life time studies and design optimization of the Ultra-low energy Storage Ring
Welsch, C. P.; Papash, A. I.; Harasimowicz, J.; Karamyshev, O.; Karamysheva, G. A.; Newton, D.; Panniello, M.; Putignano, M.; Siggel-King, M. R. F.; Smirnov, A.
2014-04-01
The Ultra-low energy electrostatic Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) will provide cooled beams of antiprotons in the energy range between 300 keV down to 20 keV. Based on the original design concept developed in 2005, the USR has been completely redesigned over the past few years by the QUASAR Group. The ring structure is now based on a 'split achromat' lattice. This ensures compact ring dimensions of 10 m × 10 m, whilst allowing both, in-ring experiments with gas jet targets and studies with extracted beams. In the USR, a wide range of beam parameters shall be provided, ranging from very short pulses in the nanosecond regime to a coasting beam. In addition, a combined fast and slow extraction scheme will be featured that allows for providing external experiments with cooled beams of different time structure. Detailed investigations into the dynamics of low energy beams, including studies into the long term beam dynamics and ion kinetics, beam life time, equilibrium momentum spread and equilibrium lateral spread during collisions with an internal target were carried out. This required the development of new simulation tools to further the understanding of beam storage with electrostatic fields. In addition, studies into beam diagnostics methods for the monitoring of ultra-low energy ions at beam intensities less than 10 6 were carried out. This includes instrumentation for the early commissioning of the machine, as well as for later operation with antiprotons. In this paper, on overview of the technical design of the USR is given with emphasis on two of the most important operating modes, long term beam dynamics and the design of the beam diagnostics system.
Energy Technology Data Exchange (ETDEWEB)
Huang, Yimei, E-mail: yhuang2@hfhs.org; Gardner, Stephen J.; Wen, Ning; Zhao, Bo; Gordon, James; Brown, Stephen; Chetty, Indrin J. [Department of Radiation Oncology, Henry Ford Health System, 2799 W Grand Boulevard, Detroit, Michigan 48202 (United States)
2015-10-15
Purpose: To present a novel positioning strategy which optimizes radiation delivery by utilizing radiobiological response knowledge and evaluate its use during prostate external beam radiotherapy. Methods: Five patients with low or intermediate risk prostate cancer were evaluated retrospectively in this IRB-approved study. For each patient, a VMAT plan with one 358° arc was generated on the planning CT (PCT) to deliver 78 Gy in 39 fractions. Five representative pretreatment cone beam CTs (CBCT) were selected for each patient. The CBCT images were registered to PCT by a human observer, which consisted of an initial automated registration with three degrees-of-freedom, followed by manual adjustment for agreement at the prostate/rectal wall interface. To determine the optimal treatment position for each CBCT, a search was performed centering on the observer-matched position (OM-position) utilizing a score function based on radiobiological and dosimetric indices (EUD{sub prostate}, D99{sub prostate}, NTCP{sub rectum}, and NTCP{sub bladder}) for the prostate, rectum, and bladder. We termed the optimal treatment position the radiobiologically optimized couch shift position (ROCS-position). Results: The dosimetric indices, averaged over the five patients’ treatment plans, were (mean ± SD) 79.5 ± 0.3 Gy (EUD{sub prostate}), 78.2 ± 0.4 Gy (D99{sub prostate}), 11.1% ± 2.7% (NTCP{sub rectum}), and 46.9% ± 7.6% (NTCP{sub bladder}). The corresponding values from CBCT at the OM-positions were 79.5 ± 0.6 Gy (EUD{sub prostate}), 77.8 ± 0.7 Gy (D99{sub prostate}), 12.1% ± 5.6% (NTCP{sub rectum}), and 51.6% ± 15.2% (NTCP{sub bladder}), respectively. In comparison, from CBCT at the ROCS-positions, the dosimetric indices were 79.5 ± 0.6 Gy (EUD{sub prostate}), 77.3 ± 0.6 Gy (D99{sub prostate}), 8.0% ± 3.3% (NTCP{sub rectum}), and 46.9% ± 15.7% (NTCP{sub bladder}). Excessive NTCP{sub rectum} was observed on Patient 5 (19.5% ± 6.6%) corresponding to localization at OM
Watanabe, Masaru; Hasegawa, Hideyuki; Kanai, Hiroshi
2002-05-01
We previously developed a method for measuring small changes in thickness of the arterial wall during one cardiac cycle. Knowledge of this change in thickness is useful for in vivo assessment of the regional elasticity of the arterial wall. In this study, from computer simulations, it is found that measurement error depends on the distance of the ultrasonic beam from the center of the artery and it can be reduced by optimally setting the focal position. In basic experiments using a silicone rubber tube and in in vivo experiments with a human carotid artery, it is found that by optimizing the focal position, measurement of the change in thickness becomes more robust against mispositioning of the ultrasonic beam. From these results, it is demonstrated that optimum focal positioning provides more robustness in measurement, even if there is arterial wall motion causing the position of the ultrasonic beam to deviate from the center of the artery.
Optimization of the tax base for corporate
Kubíčková, Alena
2012-01-01
Dissertation is oriented to optimization of basic personal income tax in a company EMIL BUREŠ HOPSERVIS Ltd. The theoretical part pays attention to introduction to tax problematics with follow-up orientation to basic personal income tax. The practical part is oriented to the analysis of costs and yield recorded in companys accountancy, furthermore calculation of real and optimized economic result and its following transformation to tax base and calculation tax obligation are realized.
Parameter Optimization Based on GA and HFSS
Institute of Scientific and Technical Information of China (English)
SUN Shu-hui; WANG Bing-zhong
2005-01-01
A new project based on genetic algorithm (GA) and high frequency simulation software (HFSS) is proposed to optimize microwave passive devices effectively. This project is realized with a general program named as optimization program. The program is compiled by Matlab and the macro language of HFSS which is a fast and effective way to accomplish tasks. In the paper, two examples are used to show the project's feasibility.
Optimization of Malicious Traffic in Optimal Source Based Filtering
Directory of Open Access Journals (Sweden)
P.MOHANRAJ
2014-01-01
Full Text Available Traffic and spam are the main problems in the data transmission through the network. Many traffic filtering systems have been proposed to find and filter the traffic over the network. The system Optimal Source Filtering (OSF has implemented a new and optimal filtering mechanism. The new mechanism named as DROP, which monitors and filters the spam and malicious traffic over a network effectively. Traffic filtering systems have been proposed to detect the spammer and malicious traffic, using the optimal rules and policies. Further these systems are highly ineffective when they encounter malicious traffic. The proposed system introduced OSF protocol, which helps to improve the efficiency of the firewall and filters based on the user rule. The proposed filtering scheme provides TFS false filtering when the flash crowd occurred. The protocol verifies users and firewall rules and policies with the data priority model, which makes the filtering process more robust and fastest manner. The Proposed spam detection project identifies and eliminates unwanted messages by monitoring outgoing messages. The spam detection is the main challenging task in the network. In the existing system spam detection has implemented after the data received. According to the user rule and request the current system identifies the spam and zombies by monitoring every outgoing message from the sender.
(RadioBiological Optimization of External-Beam Radiotherapy
Directory of Open Access Journals (Sweden)
Alan E. Nahum
2012-01-01
Full Text Available “Biological optimization” (BIOP means planning treatments using (radiobiological criteria and models, that is, tumour control probability and normal-tissue complication probability. Four different levels of BIOP are identified: Level I is “isotoxic” individualization of prescription dose at fixed fraction number. is varied to keep the NTCP of the organ at risk constant. Significant improvements in local control are expected for non-small-cell lung tumours. Level II involves the determination of an individualized isotoxic combination of and fractionation scheme. This approach is appropriate for “parallel” OARs (lung, parotids. Examples are given using our BioSuite software. Hypofractionated SABR for early-stage NSCLC is effectively Level-II BIOP. Level-III BIOP uses radiobiological functions as part of the inverse planning of IMRT, for example, maximizing TCP whilst not exceeding a given NTCP. This results in non-uniform target doses. The NTCP model parameters (reflecting tissue “architecture” drive the optimizer to emphasize different regions of the DVH, for example, penalising high doses for quasi-serial OARs such as rectum. Level-IV BIOP adds functional imaging information, for example, hypoxia or clonogen location, to Level III; examples are given of our prostate “dose painting” protocol, BioProp. The limitations of and uncertainties inherent in the radiobiological models are emphasized.
The beam-based calibration of an X-ray pinhole camera at SSRF
International Nuclear Information System (INIS)
A pinhole camera for imaging X-ray synchrotron radiation from a dipole magnet is now in operation at the Shanghai Synchrotron Radiation Facility (SSRF) storage ring. The electron beam. size is derived by unfolding the radiation image and the point spread function (PSF) with deconvolution techniques. The performance of the pinhole is determined by the accuracy of the PSF measurement. This article will focus on a beam-based calibration scheme to measure the PSF system by varying the beam images with different quadrupole settings and fitting them with the corresponding theoretical beam sizes. Applying this method at SSRF, the PSF value of the pinhole is revised from 37 to 44 μm. The deviation in beam size between the theoretical value and the measured value is minimized to 4% after calibration. This optimization allows us to observe the horizontal disturbance due to injection down to as small as 0.5 μm. (authors)
Production of a high-brightness beam using an optimized extraction system
International Nuclear Information System (INIS)
Ion beam lithography relies on high brightness beams in the micro-ampere range. For such intensities the saddle field ion source is a good choice as it offers high efficiency and easy operation. In the authors' system, two screening electrodes are enclosed between two ground electrodes and an annular anode, ensuring high operational reliability. Optimization of the extraction system was performed both by experiments and by calculations according to the rules of high current ion beam generation. The best result for nitrogen at a 13.5 keV beam energy was a 160 μA ion current with an emittance of 2.5 mm m rad. and an emittance-normalized brightness of 11.4 A/(mm m rad.)2. (author)
International Nuclear Information System (INIS)
KEK Digital Accelerator is a compact induction synchrotron which sets little limitation on the charged ion beam's species and injection velocities. Extracted from an Electron Cyclotron Resonance Ion Source (ECRIS), the ion beam (A/Q=2, 4) is transported though Low Energy Beam Transport (LEBT) line before injected into the ring for acceleration. As the velocity is relatively small (β∼10-2), effects originating from remnant fields in different magnets along the LEBT line should be taken into account for orbit correction and optics optimization. With the help of online wire monitors, the following goals have been realized: (1) Beam orbit correction; (2) Twiss parameters and emittance at a chosen position are estimated; (3) beta function and injection focusing mismatch are studied with fitted results. These processes and results are presented and discussed in this paper. (author)
Evolutionary genetic optimization of the injector beam dynamics for the ERL test facility at IHEP
Yi, Jiao
2013-01-01
The energy recovery linac test facility (ERL-TF), a compact ERL-FEL (free electron laser) two-purpose machine, was proposed at the Institute of High Energy Physics, Beijing. As one important component of the ERL-TF, the photo-injector started with a photocathode direct-current gun was designed and preliminarily optimized. In this paper an evolutionary genetic method, non-dominated sorting genetic algorithm II, is applied to optimize the injector beam dynamics, especially in the high-charge operation mode. Study shows that using an incident laser with rms transverse size of 1~1.2 mm, the normalized emittance of the electron beam can be kept below 1 mm.mrad at the end of the injector. This work, together with the previous optimization for the low-charge operation mode by using the iterative scan method, provides guidance and confidence for future constructing and commissioning of the ERL-TF injector.
Design optimization of a smooth headlamp reflector to SAE/DOT beam-shape requirements
Shatz, Narkis E.; Bortz, John C.; Dassanayake, Mahendra S.
1999-10-01
The optical design of Ford Motor Company's 1992 Mercury Grand Marquis headlamp utilized a Sylvania 9007 filament source, a paraboloidal reflector and an array of cylindrical lenses (flutes). It has been of interest to Ford to determine the practicality of closely reproducing the on- road beam pattern performance of this headlamp, with an alternate optical arrangement whereby the control of the beam would be achieved solely by means of the geometry of the surface of the reflector, subject to a requirement of smooth-surface continuity; replacing the outer lens with a clear plastic cover having no beam-forming function. To this end the far-field intensity distribution produced by the 9007 bulb was measured at the low-beam setting. These measurements were then used to develop a light-source model for use in ray tracing simulations of candidate reflector geometries. An objective function was developed to compare candidate beam patterns with the desired beam pattern. Functional forms for the 3D reflector geometry were developed with free parameters to be subsequently optimized. A solution was sought meeting the detailed US SAE/DOT constraints for minimum and maximum permissible levels of illumination in the different portions of the beam pattern. Simulated road scenes were generated by Ford Motor Company to compare the illumination properties of the new design with those of the original Grand Marquis headlamp.
Performance evaluation and optimization of BM4D-AV denoising algorithm for cone-beam CT images
Huang, Kuidong; Tian, Xiaofei; Zhang, Dinghua; Zhang, Hua
2015-12-01
The broadening application of cone-beam Computed Tomography (CBCT) in medical diagnostics and nondestructive testing, necessitates advanced denoising algorithms for its 3D images. The block-matching and four dimensional filtering algorithm with adaptive variance (BM4D-AV) is applied to the 3D image denoising in this research. To optimize it, the key filtering parameters of the BM4D-AV algorithm are assessed firstly based on the simulated CBCT images and a table of optimized filtering parameters is obtained. Then, considering the complexity of the noise in realistic CBCT images, possible noise standard deviations in BM4D-AV are evaluated to attain the chosen principle for the realistic denoising. The results of corresponding experiments demonstrate that the BM4D-AV algorithm with optimized parameters presents excellent denosing effect on the realistic 3D CBCT images.
Tiwary, Aditya; Arya, L. D.; Arya, Rajesh; Choube, S. C.
2015-03-01
This paper describes a technique for optimizing inspection and repair based availability of distribution systems. Optimum duration between two inspections has been obtained for each feeder section with respect to cost function and subject to satisfaction of availability at each load point. Teaching learning based optimization has been used for availability optimization. The developed algorithm has been implemented on radial and meshed distribution systems. The result obtained has been compared with those obtained with differential evolution.
International Nuclear Information System (INIS)
Through the Monte Carlo (MC) simulation of 6 and 10 MV flattening-filter-free (FFF) beams from Varian TrueBeam accelerator, this study aims to find the best incident electron distribution for further studying the small field characteristics of these beams. By incorporating the training materials of Varian on the geometry and material parameters of TrueBeam Linac head, the 6 and 10 MV FFF beams were modelled using the BEAMnrc and DOSXYZnrc codes, where the percentage depth doses (PDDs) and the off-axis ratios (OARs) curves of fields ranging from 4 × 4 to 40 × 40 cm2 were simulated for both energies by adjusting the incident beam energy, radial intensity distribution and angular spread, respectively. The beam quality and relative output factor (ROF) were calculated. The simulations and measurements were compared using Gamma analysis method provided by Verisoft program (PTW, Freiburg, Germany), based on which the optimal MC model input parameters were selected and were further used to investigate the beam characteristics of small fields. The Full Width Half Maximum (FWHM), mono-energetic energy and angular spread of the resultant incident Gaussian radial intensity electron distribution were 0.75 mm, 6.1 MeV and 0.9° for the nominal 6 MV FFF beam, and 0.7 mm, 10.8 MeV and 0.3° for the nominal 10 MV FFF beam respectively. The simulation was mostly comparable to the measurement. Gamma criteria of 1 mm/1 % (local dose) can be met by all PDDs of fields larger than 1 × 1 cm2, and by all OARs of no larger than 20 × 20 cm2, otherwise criteria of 1 mm/2 % can be fulfilled. Our MC simulated ROFs agreed well with the measured ROFs of various field sizes (the discrepancies were less than 1 %), except for the 1 × 1 cm2 field. The MC simulation agrees well with the measurement and the proposed model parameters can be clinically used for further dosimetric studies of 6 and 10 MV FFF beams
Network Optimization for DHT-based Applications
Sun, Yi; Yang, Y. R.; Zhang, Xiaobing; Guo, Yang; Li, Jun; Salamatian, Kavé
2012-01-01
International audience P2P platforms have been criticized because of the heavy strain that some P2P services can inflict on costly inter-domain links of network operators. It is therefore necessary to develop network optimization schemes for controlling the load generated by P2P platforms on an operator network. Previous focus on network optimization has been mostly on centralized tracker-based systems. However, in recent years multiple DHT-based P2P networks are widely deployed due to the...
International Nuclear Information System (INIS)
Inverse planning in radiation therapy is a trial and error process and many studies have been published which consider different algorithms, constraints, cases and objective functions. These planning algorithms combine in a specific way the objectives that are in conflict but do not provide the information that is necessary to obtain an optimal solution. Only in the last few years have significant increases in the availability of computing power enabled inverse planning to be performed to provide the information necessary to understand the possibilities of all dose distributions that can be obtained. We consider in this paper this multiobjective approach for external beam radiation therapy inverse planning that decouples the optimization and decision making processes. Inverse planning can now consider the number of beams, their orientation and optimal beam fluences and their dependence on importance factors. In this way it is possible to exploit the possibilities of advanced technologies such as intensity modulated radiation therapy (IMRT) or tomotherapy. Using data mining and visualization techniques a solution can be selected that requires, if possible, a small number of beams, and that also provides the required dose delivery to the target. Additionally, it allows reduction of the dose in the healthy tissue, especially in organs at risk, in such a way that the compromise we have to make for all the objectives in comparison to the best individual values is as small as possible. (author)
Optimal beam sources for Stark decelerators in collision experiments: a tutorial review
Energy Technology Data Exchange (ETDEWEB)
Vogels, Sjoerd N.; Gao, Zhi; Meerakker, Sebastiaan Y.T. van de [Radboud University, Institute for Molecules and Materials, Nijmegen (Netherlands)
2015-12-15
With the Stark deceleration technique, packets of molecules with a tunable velocity, a narrow velocity spread, and a high state purity can be produced. These tamed molecular beams find applications in high resolution spectroscopy, cold molecule trapping, and controlled scattering experiments. The quality and purity of the packets of molecules emerging from the decelerator critically depend on the specifications of the decelerator, but also on the characteristics of the molecular beam pulse with which the decelerator is loaded. We consider three frequently used molecular beam sources, and discuss their suitability for molecular beam deceleration experiments, in particular with the application in crossed beam scattering in mind. The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND{sub 3} molecules in a 2.6 meter-long Stark decelerator. We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator. We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity. (orig.)
Optimal pricing decision model based on activity-based costing
Institute of Scientific and Technical Information of China (English)
王福胜; 常庆芳
2003-01-01
In order to find out the applicability of the optimal pricing decision model based on conventional costbehavior model after activity-based costing has given strong shock to the conventional cost behavior model andits assumptions, detailed analyses have been made using the activity-based cost behavior and cost-volume-profitanalysis model, and it is concluded from these analyses that the theory behind the construction of optimal pri-cing decision model is still tenable under activity-based costing, but the conventional optimal pricing decisionmodel must be modified as appropriate to the activity-based costing based cost behavior model and cost-volume-profit analysis model, and an optimal pricing decision model is really a product pricing decision model construc-ted by following the economic principle of maximizing profit.
Structural Optimization based on the Concept of First Order Analysis
International Nuclear Information System (INIS)
Computer Aided Engineering (CAE) has been successfully utilized in mechanical industries such as the automotive industry. It is, however, difficult for most mechanical design engineers to directly use CAE due to the sophisticated nature of the operations involved. In order to mitigate this problem, a new type of CAE, First Order Analysis (FOA) has been proposed. This paper presents the outcome of research concerning the development of a structural topology optimization methodology within FOA. This optimization method is constructed based on discrete and function-oriented elements such as beam and panel elements, and sequential convex programming. In addition, examples are provided to show the utility of the methodology presented here for mechanical design engineers
Image optimization for chemical species tomography with an irregular and sparse beam array
International Nuclear Information System (INIS)
High-speed tomographic imaging of hostile engineering processes using absorption-based measurements presents a number of difficulties. In some cases, these challenges include severe limitations on the number of available measurement paths through the subject and the process of designing the geometrical arrangement of these paths for best imaging performance. This paper considers the case of a chemical species tomography system based on near-IR spectroscopic absorption measurements, intended for application to one cylinder of a multi-cylinder production engine. Some of the results, however, are also applicable to other hard-field tomographic modalities in applications where similar constraints may be encountered. A hitherto unreported design criterion is presented for optimal beam geometry for imaging performance, resulting in an irregular array with only 27 measurement paths through the subject for the engine application. Image reconstruction for this severely limited geometry is considered at length, using both simulated and experimental phantom data. Novel methods are presented for the practical generation of gaseous phantoms for calibration and testing of the system. The propane absorption coefficient at 1700 nm is measured. Quantitative imaging of propane plumes in air is demonstrated, showing good localization of circular plumes with diameter as small as 1/5 of the subject diameter and excellent imaging of multiple plumes
Directory of Open Access Journals (Sweden)
Xiangdong Qian
2012-01-01
Full Text Available Delamination is a type of representative damage in composite structures, severely degrading structural integrity and reliability. The identification of delamination is commonly treated as an issue of nondestructive testing. Differing from existing studies, a hybrid optimization algorithm (HOA, combining particle swarm optimization (PSO with simplex method (SM, is proposed to identify delamination in laminated beams. The objective function of the optimization problem is created using delamination variables (optimization parameters together with actually measured modal frequencies. The HOA adopts a hierarchical and cooperative regime of global search and local search to optimize the objective function. The PSO performs global search for objective function space to achieve a preliminary solution specifying a local potential space. Initialized by this preliminary solution, the SM executes local search for the local potential space to explore the optimal solution. The HOA is validated by a series of simulated delamination scenarios, and the results show that it can identify delamination in laminated beams with decent accuracy, reliability and efficiency. The method proposed holds promise for establishing online damage detection system beneficial for health monitoring of laminated composite structures.
Load history-based model for prestressed concrete beam damage evaluation
Institute of Scientific and Technical Information of China (English)
Yuan Jianli; Wang Yi; Qian Zhonghui
2007-01-01
The residual capability of a damaged structure to resist further load is essential in optimal seismic design and post-earthquake strengthening.An experimental study on the hysteretic characteristics of prestressed concrete frame beams under different loading histories was performed to explore the influence of load history on energy dissipation and failure characteristics of the member.Based on the test results,the failure of the beam is defined,and the relationship between the failure moment under cyclic load and from the skeleton curve is formulated.Finally,based on displacement and energy dissipation,a model for prestressed concrete beam damage-failure evaluation is developed.In this model,the effect of deformation level,cumulative dissipated energy,and loading history on prestressed concrete beam damage-failure is incorporated,thus it is applicable to stochastic earthquake forces.
Progress on Optimization of the Nonlinear Beam Dynamics in the MEIC Collider Rings
Energy Technology Data Exchange (ETDEWEB)
Morozov, Vasiliy S. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Derbenev, Yaroslav S. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Lin, Fanglei [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Pilat, Fulvia [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Zhang, Yuhong [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Cai, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Nosochkov, Y. M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Sullivan, Michael [SLAC National Accelerator Lab., Menlo Park, CA (United States); Wang, M.-H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Wienands, Uli [SLAC National Accelerator Lab., Menlo Park, CA (United States)
2015-09-01
One of the key design features of the Medium-energy Electron-Ion Collider (MEIC) proposed by Jefferson Lab is a small beta function at the interaction point (IP) allowing one to achieve a high luminosity of up to 10^{34} cm^{-2}s^{-1}. The required strong beam focusing unavoidably causes large chromatic effects such as chromatic tune spread and beam smear at the IP, which need to be compensated. This paper reports recent progress in our development of a chromaticity correction scheme for the ion ring including optimization of dynamic aperture and momentum acceptance.
Progress on optimization of the nonlinear beam dynamics in the MEIC collider rings
Energy Technology Data Exchange (ETDEWEB)
None, None
2015-07-13
One of the key design features of the Medium-energy Electron-Ion Collider (MEIC) proposed by Jefferson Lab is a small beta function at the interaction point (IP) allowing one to achieve a high luminosity of up to 10^{34} cm^{-2}s^{-1}. The required strong beam focusing unavoidably causes large chromatic effects such as chromatic tune spread and beam smear at the IP, which need to be compensated. This paper reports recent progress in our development of a chromaticity correction scheme for the ion ring including optimization of dynamic aperture and momentum acceptance.