1,059 research outputs found
Calculation of BAS-TR imaging plate responses to carbon and titanium ion beams
No full textWe calculate BAS-TR imaging plate (IP) responses to laser-accelerated heavy ion beams such as carbon ion beam and titanium ion beam. We introduce two theoretical models widely used for the prediction of an IP response. We perform Monte Carlo simulations based on these two models, and compare the predictions with the available experimental data. Our calculations of the IP response to carbon ions show discrepancy in the location of the maximum IP response, while those to titanium ions present a different slope in the IP response curve. We find that both the linear and the exponential models are insufficient to explain the measured IP responses to carbon and titanium ion beams, and attempt to explain the reason for these differences.11Nsciescopuskc
Neutron yield scaling law in laser-cluster fusion experiments
No full textWe present a scaling law ( Y ∼ E β ) of fusion neutron yields (Y) for laser pulse energy (E) in laser-cluster fusion experiments. We compare the available neutron yield data from previous deuterium cluster fusion experiments with those calculated using the cylindrical fusion plasma model. The calculated neutron yields are shown as functions of the incident laser pulse energy, average number density, and ion temperature. Although the deuterium-deuterium fusion reactivity is known to increase rapidly with ion temperature, the neutron yield shows a modest increase above ∼10 keV for a given laser pulse energy. We find the scaling exponent β approaching 1.0 as the ion temperature increases from 1 keV to 100 keV. We explain the observed temperature dependence of β by examining the temperature dependence of the beam-beam and beam-target fusion neutron yields separately. Our scaling law differs from previously reported scaling laws from individual experiments, but it shows an excellent agreement with the scaling law determined by the maximum neutron yields of individual experiments. © 2023 The Author(s). Published on behalf of IAEA by IOP Publishing Ltd.11Nsciescopu
Efficient Wear Simulation Methodology for Predicting Nonlinear Wear Behavior of Tools in Sheet Metal Forming
No full textIn conventional wear simulation, the geometry must be updated for succeeding iterations to predict the accumulated wear. However, repeating this procedure up to the desired iteration is rather time consuming. Thus, a wear simulation process capable of reasonable quantitative wear prediction in reduced computational time is needed. This study aimed to develop an efficient wear simulation method to predict quantitative wear reasonably in reduced computational time without updating the geometry for succeeding iterations. The wear resistance of a stamping tool was quantitatively evaluated for different punch shapes (R3.0 and R5.5) and coating conditions (physical vapor deposition of CrN and AlTiCrN coatings) by using a progressive die set. To capture the nonlinear wear behavior with respect to strokes, a nonlinear equation from a modified form of Archard’s wear model was proposed. By utilizing the scale factor representing the changes in wear properties with respect to wear depth as input, the simulation can predict the behavior of rapidly increasing wear depth with respect to strokes after failure initiation. Furthermore, the proposed simulation method is efficient in terms of computational time because it does not need to perform geometry updates
Time-resolved Rayleigh scattering measurements of methane clusters for laser-cluster fusion experiments.
No full textWe present a time-resolved analysis of Rayleigh scattering measurements to determine the average size of methane clusters and find the optimum timing for laser-cluster fusion experiments. We measure Rayleigh scattering and determine the average size of methane clusters varying the backing pressure (P0) from 11 bar to 69 bar. Regarding the onset of clustering, we estimate that the average size of methane clusters at the onset of clustering is Nc0≅20 at 11 bar. According to our measurements, the average cluster radius r follows the power law of r∝P01.86. Our ion time-of-flight measurements indicate that we have produced energetic deuterium ions with kT = 52±2 keV after laser-cluster interaction using CD4 gas at 50 bar. We find that this ion temperature agrees with the predicted temperature from CD4 clusters at 50 bar with r = 14 nm assuming the Coulomb explosion model
Rapid, uniform, and efficient heat transfer into dense matter using energetic proton beams with finite energy spreads
No full text© 2022 Elsevier LtdEnergetic charged particles such as laser-driven protons or ions can transfer heat into a small solid-density sample very quickly, sometimes heating it to temperatures beyond 10,000 K. Uniform and efficient heat transfer would be desirable when measuring the physical properties of the sample after heating, but heating a thick solid-density sample both uniformly and efficiently in a short time has been very challenging. Here we show that a thick (> 1 cm) solid-density aluminum sample can be heated rapidly, uniformly, and efficiently all at the same time using an energetic proton beam with a finite energy spread. We perform Monte Carlo simulations to study the relationship between the energy spread of the incident protons and the heat transferred onto the sample for rapid, uniform, and efficient heating. We find that a 100 MeV proton beam with a Gaussian energy spread of ΔE/E ~ 70% can transfer heat into a 32 mm thick solid-density aluminum sample uniformly (temperature nonuniformity 62% heat transfer efficiency) on a sub-nanosecond time scale.11Nsciescopu
Monte carlo study of imaging plate response to laser-driven aluminum ion beams
No full textWe measured the response of BAS-TR imaging plate (IP) to energetic aluminum ions up to 222 MeV, and compared it with predictions from a Monte Carlo simulation code using two different IP response models. Energetic aluminum ions were produced with an intense laser pulse, and the response was evaluated from cross-calibration between CR-39 track detector and IP energy spectrometer. For the first time, we obtained the response function of jthe BAS-TR IP for aluminum ions with a kinetic energy as high as 222 MeV. On close examination of the two IP response models, we confirm that the exponential model fits our experimental data better. Moreover, we find that the IP sensitivity in the exponential model is nearly constant in this energy range, suggesting that the response function can be determined even with little experimental data.11Nsciescopu
Efficient Bang-Bang Model Predictive Control for Quadcopters
No full textTime-optimal model predictive control is important for achieving fast racing drones but is computationally intensive and thereby rarely used onboard small quadcopters with limited computational resources. In this work, we simplify the optimal control problem (OCP) of the position loop for several maneuvers by exploiting the fact that the solution resembles a so-called ‘bang-bang’ in the critical direction, where only the switching time needs to be found. The noncritical direction uses a ‘minimum effort’ approach. The control parameters are obtained through bisection search schemes on an analytical path prediction model. The approach is compared with a classical PID controller and theoretical time-optimal trajectories in simulations. We explain the effects of the OCP simplifications and introduce a method of mitigating one of these effects. Finally, we have implemented the ‘bang-bang’ controller as a model predictive controller (MPC) onboard a Parrot Bebop and performed indoor flights to compare the controller’s performance to a PID controller. We show that the light novel controller outperforms the PID controller in waypoint-to-waypoint flight while requiring only minimal knowledge of the quadcopter’s dynamics.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Control & Simulatio
Marketing Communications Plan for a Fintech company. Case: Rundit Oy
No full textThe objective of this thesis was to analyze the operations and strategies of fundraising in the financial aspect. How companies communicate with their investors, how a Fintech company can help and enhance the connection between them.From there, the thesis will propose the marketing communications strategy that might im-prove the number of userbase, attract more companies and investors to join the platform, and further increase customer awareness. The conclusion includes the analysis of the com-pany’s current situation, the company's strengths, and its core values, identify the goal, vision, and strategic plan. More precisely, the author sought for the correct core values of the company to improve the effectiveness of online marketing communications.The thesis is commissioned by Rundit Oy, a Finnish Fintech startup. They provide a platform that can improve communication between investors and companies. Their aim is to create a platform where the investors can have a better overview and situation of the companies that they have invested in by standardizing the process of the financial report, metrics, charts, and forecasts, etc. Furthermore, they also help the company to promote themselves, to be able to open the fundraising, to connect them with potential investors, and provide them a professional tool for investor reporting.The author uses the qualitative research method that focuses on Participator observation method and conducts a series of Semi-structured interviews to gather data. The interview involved the CEO, Product owner, and lead designer of Rundit. After gathering the necessary data, the author will draw the Business Model Canvas to identify the current value of the company, then use different analyses such as SWOT and PESTEL to support making the mar-keting communications plan
Second-order analysis and numerical approximation for bang-bang bilinear control problems
No full textWe consider bilinear optimal control problems whose objective functionals do not depend on the controls. Hence, bang-bang solutions will appear. We investigate sufficient secondorder conditions for bang-bang controls, which guarantee local quadratic growth of the objective functional in L1 . In addition, we prove that for controls that are not bang-bang, no such growth can be expected. Finally, we study the finite-element discretization and prove error estimates of bang-bang controls in L1 -norms.The first author was partially supported by the Spanish Ministerio de Economía Industria y Competitividad under research projects MTM2014-57531-P and MTM2017-83185-P. The second author was partially supported by DFG under grant Wa 3626/1-1
Electron-positron generation by irradiating various metallic materials with laser-accelerated electrons
No full textWe examined electron–positron pair production in solid iron, zinc, tungsten, and lead targets irradiated by a laser-accelerated electron beam generated with a 100 TW laser. These targets were assessed at the target thickness of 0.5, 1.25, and 2.0 radiation lengths for each material. Using a 0.75-T-magnetic spectrometer, we measured the electron and positron yields and spectra, producing 3 × 108 positrons per shot with a peak leptonic density of 4 × 1012 cm−3. These experimental results agree very well with Monte Carlo simulations conducted with the simulation code Geant4. Importantly, our findings show that normalizing the target thickness to each material's radiation length results in consistent electron and positron yields across the materials, effectively reducing discrepancies due to material differences. © 2023 The Author(s)11Nsciescopu
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