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Study of the germanium dead layer influence on HP(Ge) detector efficiency by Monte Carlo simulation
摘要： Introduction The dead layer thickness provided by the manufacturer increases with the aging of the HPGe detector; the increase of dead layer thickness leads to the decrease in the detector’s ef?ciency, not only due to gamma rays attenuation in the dead layer but also due to the reduction of the active volume of the detector. Purpose In this work, the dead layer in?uence on HPGe detector ef?ciency was studied by Monte Carlo simulation. Materials and methods The detector model was developed using Monte Carlo N Particle (MCNP5) code for adjustment of the dead layer thickness; the adjustment was performed according to a speci?c irradiation con?guration by collimation approach using three reference point sources: 241Am (59.5 keV), 137Cs (661.6 keV) and 60Co (1173.2 keV; 1332.5 keV). Result The calculated ef?ciencies were compared to the measured intrinsic ef?ciency ones for these point sources; a good agreement between Monte Carlo and measurements results was found after the experimental validation. Conclusion The results con?rm the variation in the dead layer thickness according to aging of the detector; the average change of dead layer is in order of 1.30 ± 0.05 mm after 9 years.
关键词： Dead layer thickness,Detector ef?ciency,Monte Carlo simulation,Point sources,HPGe detector
更新于2025-09-23 15:21:01
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Nanostructures for Cancer Therapy || Dose enhancement effect in radiotherapy: adding gold nanoparticles to tumor in cancer treatment
摘要： The rationale of radiation dose enhancement due to gold nanoparticle addition in radiotherapy is revealed from the basic particle interactions to Monte Carlo simulation. Our review of different radiobiological studies on Monte Carlo, cell line, and preclinical model confirms that cancer cell kill definitely benefits from the dose enhancement when gold nanoparticles were added. Moreover, such dose enhancement depends on the size, shape, and concentration of the gold nanoparticle, as well as the type and energy of the radiation beams. It is concluded that adding gold nanoparticles to the tumor can enhance both the dose and contrast at the target in radiotherapy.
关键词： radiotherapy,cancer treatment,Monte Carlo simulation,gold nanoparticles,dose enhancement
更新于2025-09-23 15:21:01
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A study of deformation behavior and phase transformation in 4H-SiC during nanoindentation process via molecular dynamics simulation
摘要： The deformation behavior and phase transformation of 4H silicon carbide (4H-SiC) during nanoindentation process is investigated with a cube corner diamond indenter through molecular dynamics simulation. It is found through the research that the basal dislocations are most likely to be generated in (0001) face and the indentation process contributes to the distortion of 4H-SiC lattice. In addition, phase transformation from 4H-SiC to 3C-SiC is firstly observed via MD simulations during indentation process. Cross-sectional observation in (12 10) plain shows that 3C-SiC layers appear firstly during nanoindentation process, and the layers are observed at small indentation depth. 3C-SiC grain is generated based on 3C-SiC layers, and the transformation is more likely to appear at larger indentation depth. The phase transformation from 4H-SiC to 3C-SiC results from the shear stress induced by indenter during loading process. 3C-SiC grain and layers are both generated from the slip of 3C seeds under the influence of shear stress, and the condition of 3C-SiC grain formation is stricter. Moreover, the P-h curve is studied and the vertical deformation mode during indentation process on 4H-SiC can be reflected on P-h curve as small pop-in events. The findings are meaningful for the study of deformation mechanism of SiC and the application of SiC in precision machining.
关键词： molecular dynamics simulation,cube corner diamond indenter,3C-SiC grain,4H-SiC,phase transformation,3C-SiC layer
更新于2025-09-23 15:21:01
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A method for energy modeling and simulation implementation of machine tools of selective laser melting
摘要： Additive manufacturing (AM) technologies are providing promising solutions to production of unique parts at reduced material and energy consumptions. However, recent studies show that the sustainable advantage of AM is not always achieved. For ensuring the sustainability of the AM processes, quantification and assessment of the levels of resource consumptions should be carried out at the design phase. To enable the energy prediction and evaluation of AM, this work proposes a method for energy modeling and simulation implementation of AM machines and applies the method to a machine tool of selective laser melting (SLM). Furthermore, the developed simulation approach is validated using an experimental comparison and has been applied in a use case to realize an energy efficiency-oriented AM process design.
关键词： bond graph,energy simulation,selective laser melting,additive manufacturing,power flow modeling
更新于2025-09-23 15:21:01
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Numerical simulation of multilayer organic light-emitting diodes with hosta??guest emissive layer: the role of defect states
摘要： In this study, a comprehensive model for the numerical simulation of electrical and optical characteristics of multilayer organic light-emitting devices (OLED) is presented. The model consists of three parts: charge carrier transport model, exciton model, and a post-processing part for calculating luminance. The defect states in the organic layers are modeled and are introduced into the equations. For demonstrating the rule of the defect states in such devices, a multilayer OLED is considered consisting of a host–guest emissive layer sandwiched between electron and hole transport layers. The current density and luminance results of the analyzed device are compared with the experimental data. We have found that by considering the defect states, there is good accordance between the simulation results and the experimental data.
关键词： Host–guest emissive layer,Luminance,Current density,OLED,Numerical simulation,Defect states
更新于2025-09-23 15:21:01
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Simulation of 3D-Silicon sensors for the TIMESPOT project
摘要： The experimental conditions in future High Luminosity LHC experiments require new detector systems with increased performances compared to the current state of the art. In this context, increasing spacial resolution and including time measurement with a resolution of less than 50 ps for particle tracking systems can avoid false track reconstruction due to event pileup. For this kind of future tracking detectors the 3D silicon sensor technology appears as a good option. In this context the TIMESPOT initiative was launched. Concerning the development of the sensor, different geometrical solutions have been explored and simulated to optimize the timing response of the single pixel sensor using Sentaurus TCAD. The configuration with the best electric field characteristics for timing was selected for signal simulation. In order to compensate the very time-consuming behavior of TCAD simulations, a faster charge transport simulator with TCAD and Geant4 support is under development. Further sensor configurations, including a first primitive capacitive and resistive load, were also simulated and evaluated. This paper shows a general overview of the project with particular attention to the silicon sensor development. First results are presented.
关键词： Fast timing tracking,3D silicon sensors,Tracking detectors,sensor simulation,TCAD
更新于2025-09-23 15:21:01
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Design, fabrication and characterization of a windowless extrapolation chamber for low-energy X-rays: Experimental and Monte Carlo results
摘要： Extrapolation chamber is a special parallel-plate ionization chamber, particularly suggested for low penetrating radiations. Its sensitive volume is varied through a change of the inter-electrode distance, ideally satisfying the Bragg-Gray cavity theory. A windowless extrapolation chamber was designed and constructed for low-energy X-rays, produced at the tube voltage of 70-100 kV. It consists of the following elements and innovation. The electrodes of the chamber are made of a homogenous block of graphite instead of a coating graphite layer to reduce the leakage current. Also, the entrance window has been eliminated to decrease the beam perturbation. To the best of our knowledge, this type of chamber has not been used in low energy X-rays before. The performance of the chamber was investigated in terms of its saturation curve, polarity effect, leakage current, linearity of response and short-term stability. It was also simulated using Monte Carlo method and in the worst case, the relative ionization current obtained in experiment differs about 4.5% with that in the simulation result. Moreover, the influence of chamber components on its response was examined. All of the results showed the feasibility of its use for detection of 70 - 100 kV X-rays.
关键词： simulation,Low-energy X-rays,Monte Carlo,Extrapolation chamber,dosimetry
更新于2025-09-23 15:21:01
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Terahertz and Infrared Spectroscopy of Dense and Porous Organosilicate Glass Thin Films
摘要： Wide-range measurements of thin films of SiCxOyHz organosilicate glasses, both dense and porous, deposited on dielectric sapphire substrates and conductive layers of platinum and aluminum, were performed in the THz–IR (5–5000 cm–1) range. This method can be used not only to analyze the evolution of absorption bands in amorphous dielectric films but also to evaluate static conductivity in the framework of the Drude model of conductive layers and to determine the electrodynamic characteristics of organosilicate films with low dielectric permittivity. The original approach proposes a comprehensive analysis of experimental broadband data in order to determine not only the parameters of the individual bands of lattice and molecular vibrations but also the integrated electrodynamic characteristics of the samples obtained.
关键词： simulation of dielectric response spectra,terahertz and infrared spectroscopy,thin films,low-k materials
更新于2025-09-23 15:21:01
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Prediction of solidification cracking by an empirical-statistical analysis for laser cladding of Inconel 718 powder on a non-weldable substrate
摘要： This paper presents an empirical-statistical approach to predict solidification cracking during laser cladding of Inconel 718 powder on A-286 Fe-based superalloy. This approach is based on a linear regression analysis and empirical-statistical correlations between the key processing parameters (laser power, P; powder feed rate, F; and scanning speed, V) and the geometrical attributes of single laser cladding tracks. These correlations were used for the development of a processing map which assesses the effects of the geometrical characteristics on the solidification cracking and the required conditions to obtain crack-free clads. Scanning electron microscopy was used for microstructural characterization. Thermodynamic calculations using the non-equilibrium Scheil solidification model were also employed. The empirical-statistical analysis showed that the processing parameters directly associated with the height and angle of single laser cladding tracks are and, respectively. The processing map revealed that the dilution ratio is the governing macrostructural attribute required to avoid solidification cracking. Indeed, a substrate dilution ratio lower than 25% shifts the cladding composition to an alloy regime, which has lower susceptibility to solidification cracking. The role of this macrostructural feature in reducing the susceptibility of the fusion zone to solidification cracking is thoroughly discussed.
关键词： Thermodynamic simulation,Inconel 718,Processing map,Solidification cracking,Laser cladding,Dilution ratio
更新于2025-09-23 15:21:01
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Numerical simulation of temperature field of B1500HS steel/Q235 laser tailored blanks by external thermal action
摘要： Taking high-strength B1500HS steel/Q235 laser tailored blanks as the research object, this paper established the finite element model of the laser welding process of high-strength B1500HS steel /Q235 laser tailored blanks based on the theoretical model of laser welding temperature field. The temperature field of laser tailored blanks was numerically simulated under the conventional condition and External Thermal Action (ETA). The thermal cycle curve of welded joints was compared and analyzed, and the influence of welding power and welding speed on the welding width was analyzed. The results show that, under ETA condition, the cooling rate of weld and heat affected zone decreases greatly, and the residence time above the phase transition temperature becomes longer. And it is conducive to the homogenization of austenite structure at high temperature and the coordination of mechanical properties of welded joints. In addition, under the same welding power, the welding width of ETA is wider than that of conventional welding, and the larger the welding speed is, the smaller the welding width is. In order to ensure the penetration of welding, the welding speed should between 2mm/s and 7mm/s.
关键词： laser welding,external thermal action,cooling rate,numerical simulation,temperature field
更新于2025-09-23 15:21:01