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[IEEE 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Honolulu, HI, USA (2018.7.18-2018.7.21)] 2018 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) - Study of the photoneutron generation caused by a LinAc Beryllium window with a 6 MeV treatment beam
摘要： In most conventional radiation therapy treatments, special attention is payed for neutron contamination when working with energy beams above 8 MeV and generally it is only considered for shielding requirements, not for dose study in patients or employees. The present work is focused on studying the unwanted generated photoneutrons in a Medical Linear Accelerator (LinAc) Varian TrueBeam using a 6 MeV radiation treatment beam. To that, Monte Carlo (MC) simulation code MCNP6.1.1 was used. This version of the code allows the use of unstructured mesh geometries as a novelty, offering more reliable results and higher speed computation. The particularity of the studied LinAc is the presence of a beryllium filter at the treatment head. Since Beryllium causes photonuclear reactions (γ, n) at energies much lower than other LinAc composing materials, this work aims to analyze if this type of units, when using low energy treatment beams (6 MeV), produce neutron pollution and to ensure that this unwanted radiation can be considered negligible.
关键词： Monte Carlo simulation,Medical Linear Accelerator,radiation therapy,photoneutrons,Beryllium filter
更新于2025-09-09 09:28:46
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DUAL-CHIRP ARBITRARY MICROWAVE WAVEFORM GENERATION BY USING A DUAL PARALLEL MACH-ZEHNDER MODULATOR FEEDING WITH RF CHIRP SIGNAL
摘要： In this paper, dual-chirped arbitrary microwave waveform has been generated through photonics, incorporated with single dual parallel mach-zehnder modulator (DPMZM) inbuilt mach zehnder interferometer (MZI) structure. We have taken two cases of chirping, i.e., linear and nonlinear chirps. A case of linear chirping has been explored previously. However, to the best of the authors’ knowledge e?ect of nonlinear chirping in this paper is evaluated for the ?rst time. Other photonics approaches are also available, such as spectra shaping and wavelength to time mapping. But due to ?xed spectral response of spectral shaper, center frequency of linear chirp generated waveform is ?xed. To get large center frequency again we have to use large number of spectral shapers which will increase the system complexity. DPMZM avoids such di?culties. These MZMs are biased at the minimum transmission point to get carrier suppressed modulation. Product modulator (PM) is cascaded to the lower arm of DPMZM. Here by using DPMZM we get two advantages. First we have two complimentarily chirped microwave waveforms and second up conversion of the frequency of microwave carrier. A dual-chirped microwave waveform with centre frequency 6 GHz with bandwidth 200 MHz and 2 GHz is generated. The paper gives speci?c details about various performance parameters such as input signal frequency and power, output signal parameters viz output frequency, chirp rate, chirp bandwidth, time bandwidth product (TBW), etc. The overall model and its performance parameters are computed through MATLAB simulation.
关键词： DPMZM,dual-chirped microwave waveform,linear chirping,photonics,nonlinear chirping,MATLAB simulation
更新于2025-09-09 09:28:46
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A METHOD FOR ICE-THICKNESS DETECTING AND ICE-SECTION IMAGING BY USING FMCW-SAR ALGORITHM
摘要： Sea ice plays an important role in global climate. Many researches focus on the measurement of the sea ice thickness. In this paper, we present a method for the ice-detecting combining frequency-modulated continuous-wave (FMCW) technology and synthetic aperture radar (SAR) technology. It can provide a good resolution both in the range dimension and the azimuth one. Then a simulation is conducted to verify the accuracy and the feasibility of this algorithm. The physical properties of the sea ice, such as re?ection and scatter properties of the ice surface and the transmission characteristic when the electromagnetic wave travels through the ice, are considered in the simulation. The results of the simulation demonstrate that this algorithm has a good performance in ice penetrating.
关键词： FMCW-SAR,simulation,ice thickness detection,sea ice
更新于2025-09-09 09:28:46
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[Papers] Quantum Efficiency Simulation and Electrical Cross-talk Index Development with Monte-Carlo Simulation Based on Boltzmann Transport Equation
摘要： This paper explains a new method to model a photodiode for accurate quantum efficiency simulation. Individual photo-generated particles are modeled by Boltzmann transport equation, and simulated by Monte-Carlo method. Good accuracy is confirmed in terms of similarities of quantum efficiency curves, as well as color correction matrices and SNR10s. Three attributes - "initial energy of the electron", "recombination of electrons at the silicon surface" and "impurity scattering" - are tested to examine their effectiveness in the new model. The theoretical difference to the conventional method with drift-diffusion equation is discussed as well. Using the simulation result, the relationship among the cross-talk, potential barrier, and distance from the boundary has been studied to develop a guideline for cross-talk suppression. It is found that a product of the normal distance from the pixel boundary and the electric field perpendicular to the Z-axis needs to be more than 0.02V to suppress the probability of electron leakage to the adjacent pixel to less than 10%.
关键词： cross-talk,quantum efficiency,simulation,image sensor,BTE,Boltzmann transport equation
更新于2025-09-09 09:28:46
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A model for charge transport in semicrystalline polymer thin films
摘要： A model for simulating the charge transport properties of semicrystalline polymer (SCrP) using Monte Carlo simulation is reinvented. The model is validated by reproducing the experimentally observed ?eld and temperature dependence of mobility in Poly(3-hexylthiophene-2,5-diyl) (P3HT) thin ?lms. This study also provides a new physical insight to the origin of much debated negative ?eld dependence of mobility (NFDM) observed at low electric ?eld strengths in P3HT thin ?lms. The observed NFDM, which is not explainable with the mechanisms proposed earlier, is attributed to the weak dependence of transit time on the applied electric ?eld strengths. In the semicrystalline ?lms, the charge transport takes place mostly through the crystalline regions, in which the charge transport is weakly dependent on the strength of the applied electric ?eld. In addition, a possible explanation for the origin of Arrhenius temperature dependence of mobility (lnμ / 1/T) commonly observed in SCrP thin ?lms is also proposed.
关键词： Monte Carlo simulation,charge transport,poly(3-hexylthiophene-2,5-diyl),semicrystalline polymers,negative ?eld dependence of mobility
更新于2025-09-09 09:28:46
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Correlation between thermal-vibration-induced large displacement of Cu atoms and phase transition in Cu4SnS4: First-principles investigation
摘要： First-principles (FP) calculations and first-principles molecular dynamics (FPMD) simulations for Cu4SnS4 were performed to clarify the origin of the structural phase transition at 232 K between the high-temperature phase (HP) and low-temperature phase (LP), which leads to an experimentally measured drastic change in the transport properties of Cu4SnS4. The results of the FP and PFMD calculations indicated that, rather than being caused by the so-called freezing of soft modes, the key driving force behind the phase transition in Cu4SnS4 is a large-scale displacement of the Cu atoms located at particular sites due to thermal vibration. In fact, tetrahedrally coordinated CuS4 is stabilized by the effect of the thermal vibration of Cu atoms in the HP whereas CuS3, which is in a trigonal planar environment, is stabilized in the LP.
关键词： first-principles calculation,molecular dynamics simulation,thermoelectric property,electronic structure,phase transition
更新于2025-09-09 09:28:46
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Dynamic simulation, control, and performance evaluation of a synergistic solar and natural gas hybrid power plant
摘要： Solar power is considered among the leading renewable energy technologies. Abundant supply, flexibility of installation, and decreasing cost makes it an interesting renewable energy resource. However, there are challenges associated with the reliability of solar power due to its intermittent nature. This work demonstrates the synergies that exist in integrated hybrid systems, where a dispatchable fuel is used in conjunction with concentrated solar power. In this simulation-based study, a parabolic trough solar concentrator is used to collect solar energy. The heat collected from the solar field is used to generate steam in a Rankine cycle. The system also utilizes natural gas combustion in the steam generator to provide supplemental steam when the solar intensity is reduced due to cloud cover or at night. Natural gas is also used for superheating the steam, which allows the system to produce higher temperatures and achieve increased thermodynamic cycle efficiencies. This flexible design produces 100 MW at nominal conditions, while it is capable of producing a maximum of 140 MW when sufficient solar energy is available. The novel contributions of this work include a complete, systems-level, dynamic model of a hybrid solar plant. The model is complete with a control system that smoothly transitions the plant from pure natural gas mode at night to solar hybrid mode during the day. It evaluates innovative design features such as flexible fuel operation, steam superheating to boost efficiency, and preheating by solar or waste heat. Furthermore, this work demonstrates that by hybridizing a solar system with a dispatchable energy source, both the reliability and efficiency of the solar power production are increased. The annual solar-to-electric efficiency increases from 15.2% to 26.13% with hybridization, which indicates that utilization of the solar energy is effectively increased.
关键词： Natural gas plant,Hybrid system,Dynamic simulation and control,Concentrated solar power
更新于2025-09-09 09:28:46
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Tomography-based determination of Nusselt number correlation for the porous volumetric solar receiver with different geometrical parameters
摘要： Pore-scale numerical models of the porous volumetric solar receiver are established in this paper. By using the X-ray computed tomography and the imaging processing techniques, models of porous media with different geometrical parameters are reconstructed. The conjugate heat transfer process in the porous volumetric solar receiver is solved based on the direct pore-scale numerical simulation. The turbulent effect of fluid flow inside porous geometry is considered by the Shear-Stress Transport k-ω model and the absorbed solar energy is simulated by following the Beer’s law. The results present that the inlet velocity and the geometrical parameters influence the thermal performance of the porous volumetric solar receiver. Larger inlet velocity tends to enhance the convective heat transfer between fluid and solid phases meanwhile decreases noticeably the overall temperature. Receiver with larger porosity is preferred because it limits the reflection losses. The Nusselt number increases as the porosity becomes larger. As a result, the general correlation of Nusselt number for the porous volumetric solar receiver is derived as a function of porosity and Reynolds number. This correlation is applicable with the porosity ranging from 0.74 to 0.89 and the pore Reynolds number ranging from 3 to 233.
关键词： Solar energy,Pore-scale numerical simulation,Convective heat transfer,Volumetric solar receiver,Nusselt number correlation,Porous media
更新于2025-09-09 09:28:46
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Concise Approach for Determining the Optimal Annual Capacity Shortage Percentage using Techno-Economic Feasibility Parameters of PV Power System
摘要： PV power systems have been commercially available and widely used for decades. The performance of a reliable PV system that fulfils the expectations requires correct input data and careful design. Inaccurate input data of the techno-economic feasibility would affect the size, cost aspects, stability and performance of PV power system on the long run. The annual capacity shortage is one of the main input data that should be selected with careful attention. The aim of this study is to reveal the effect of different annual capacity shortages on the techno-economic feasibility parameters and determining the optimal value for Baghdad city location using HOMER simulation tool. Six values of annual capacity shortage percentages (0%, 1%, 2%, 3%, 4%, and 5%), and wide daily load profile range (10 kWh - 100 kWh) are implemented. The optimal annual capacity shortage is the value that always “wins” when each techno-economic feasibility parameter is at its optimal/ reasonable criteria. The results showed that the optimal annual capacity shortage that reduces significantly the cost of PV power system while keeping the PV system with reasonable technical feasibility is 3%. This capacity shortage value can be carried as a reference value in future works for Baghdad city location. Using this approach of analysis at other locations, annual capacity shortage can be always offered as a reference value for those locations.
关键词： optimal annual capacity shortage,effect of different annual capacity shortages,PV power system,techno-economic feasibility parameters,HOMER simulation tool
更新于2025-09-09 09:28:46
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THE DEVELOPMENT OF A NOVEL ARRAY DETECTOR FOR OVERCOMING THE DOSIMETRY CHALLENGES OF MEASURING IN VERY SHORT PULSED CHARGED PARTICLE BEAMS: THE ELIDOSE PROJECT
摘要： In-beam dose measurements are paramount for any application seeking to harness the effects of the radiation beam, so all the future applications of the laser accelerated beams (as generated in the ELI and CETAL projects) will need such measurements. With a very long history in measuring doses in charged particle beams, the medical and industrial applications setup a number of methods that could be also used for the dosimetry of the beams generated by laser pulses. Dose measurements rely heavily on what is seen as the gold standard in dose measurement: the ion chambers. Ion chambers have both limitations and advantages, and in our case the disadvantage could be the large number of corrections to be applied in order to calculate a correct dose from the measured charge. The ELIDOSE project tries to address these problems by proposing an array detector that would allow the simultaneous measurement of the recombination and polarity corrections, and of the dose. The detector consists of four identical ion chambers mounted together in a PMMA frame and the project will analyze its response to various charged particle beams and the reciprocal influences of the chambers on each other. These reciprocal influences of the four chambers are studied through the FLUKA modeling of the detector and, in order to hone the simulations of the detectors, we initially compared the results of the measurements performed with an Advanced MarkusTM chamber in the proton beam delivered at the 3-MV TandetronTM from IFIN-HH. The paper presents the results of these initial measurements and how these results will be used to modify the simulation parameters.
关键词： dosimetry,ELIDOSE project,charged particle beams,FLUKA simulation,ion chambers
更新于2025-09-09 09:28:46