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Investigation into effect of coupled resonance phenomenon towards sensitivity enhancement of SAW conductivity sensors integrated with ZnO nanorods
摘要： In this work, FEM simulation was used to investigate the sensitivity of a one-port surface acoustic wave (SAW) resonator sensor to changes in electrical conductivity of the sensing medium composed of ZnO nanorods offering elastic loading on the surface of the resonator. A system of coupled resonators was formed when the height of the ZnO nanorods attached to the surface of the resonator was adjusted such that the resonant frequency of the nanorod approached the original resonant frequency of the SAW resonator. It was observed that the use of ZnO nanorods of resonant dimensions as sensing medium could enhance the sensitivity of the composite SAW sensor to changes in electrical conductivity of the sensing medium by up to 79 times. The comparatively higher sensitivity of the SAW conductivity sensor utilizing ZnO nanorods at resonant dimensions as sensing medium was attributed to the fact that the system of coupled resonators thus formed operates at a state of high sensitivity to changes induced in piezoelectric stiffening of the substrate during SAW propagation. The observations from FEM simulation conducted in the present work suggests strong prospects for the use of coupled resonance phenomenon at nanoscale for enhancing the sensitivity of conductivity-based SAW gas sensors and UV detectors employing 1-D ZnO nanostructures as sensing medium.
关键词： ZnO nanorods,sensitivity enhancement,SAW resonator,coupled resonance,FEM simulation
更新于2025-09-23 15:19:57
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Laser Trapping of Circular Rydberg Atoms
摘要： Rydberg atoms are remarkable tools for quantum simulation and computation. They are the focus of an intense experimental activity, mainly based on low-angular-momentum Rydberg states. Unfortunately, atomic motion and levels lifetime limit the experimental timescale to about 100 μs. Here, we demonstrate two-dimensional laser trapping of long-lived circular Rydberg states for up to 10 ms. Our method is very general and opens many opportunities for quantum technologies with Rydberg atoms. The 10 ms trapping time corresponds to thousands of interaction cycles in a circular-state-based quantum simulator. It is also promising for quantum metrology and quantum information with Rydberg atoms, by bringing atom-field interaction times into unprecedented regimes.
关键词： circular Rydberg states,quantum computation,Rydberg atoms,quantum simulation,laser trapping
更新于2025-09-23 15:19:57
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Hot cracking in autogenous welding of 6061-T6 aluminum alloy by rectangular pulsed Nd:YAG laser beam
摘要： Due to high hot crack susceptibility of Al-Mg-Si alloys, autogenous welding by rectangular pulsed laser beam has not been generally successful in the removal of cracks. In this research, the effect of pulsed Nd:YAG laser parameters and preheating on the creation of hot cracks in the 6061-T6 aluminum alloy was investigated. The sample that was fabricated by the laser parameters including 1 Hz, 0.12 mm/s, 10 ms, and without preheating exhibited the highest cooling rate and the smallest dendrite arm spacing but no hot crack was observed. The tensile test specimens of this sample fractured at a point far from the weld metal and a decrease in the precipitation of silicon and magnesium in the inter-dendritic space and the reduction of thermal stresses resulted in the elimination of hot cracks. However, according to macro-scale models for the creation of hot cracks, preheating decreased the tensile stresses in the BTR (brittle temperature range), but increasing the preheating temperature led to increasing rather than decreasing the hot crack length. In this case, the formation of hydrogen porosity, the segregation of silicon and magnesium, and the creation of low melting point compounds were the important parameters affecting the hot crack initiation and growth.
关键词： Laser welding,6061 aluminum alloy,Stress simulation,Solidification microstructure,Hot crack modeling,Rectangular pulse
更新于2025-09-23 15:19:57
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Mesoscopic study of thermal behavior, fluid dynamics and surface morphology during selective laser melting of Ti-based composites
摘要： A mesoscopic simulation based on the randomly packed powder bed model was developed to study the thermal behaviors during selective laser melting (SLM) of Ti-based composites. Effects of processing parameters on the thermal behavior, fluid dynamics and surface morphology evolution within the molten pool were investigated. The obtained results revealed that the operating temperature, cooling rate and melt lifetime were highly enhanced as the laser power was increased. Meanwhile, the increased molten pool dimensions, the turbulent fluid flows, the improved escaping rate of the entrapped gas and the efficient rearrangement of reinforcing particles within the molten pool appeared at the application of the high laser power. At the optimized processing parameters, the peak of the operating temperature profile located in the laser and powder interaction area was apparently disappeared with the formation of the maximum temperature of 3300 K and, the mean operating temperature of the platform caused by the heat accumulation was as high as 1300 K. Moreover, the surface morphology of the molten pool predicted by the simulation showed a variation from continuous pores to fragments, then to the typical and regular liquid front, and finally to the turbulent liquid front and spatter and balling phenomenon as the laser power increased. At the laser power of 200 W and laser energy density of 140 J/m, the maximum velocity was located in the front and rear region and, the velocity vector located in the melt advanced front pointed to the rear region of the molten pool, indicating that the melt from the irradiation region would complete the efficient melt supplement and avoid the formation of residual pores and therefore, a good and flat surface with few spatters was obtained with the clear liquid front. The simulated surface morphology was found to be consistent with the experimental measurements.
关键词： Surface morphology,Thermodynamics,Mesoscopic simulation,Selective laser melting,Titanium matrix composite
更新于2025-09-23 15:19:57
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Recent Problems of Heat-Transfer Simulation in Technological Processes of Selective Laser Melting and Fusion
摘要： The thermal processes arising upon the implementation of the additive technologies of selective laser melting and the fusion of metals and alloys are analyzed. An adequate description of the heat transfer upon the implementation of additive technological processes associated with high-intensity local heating by a moving laser beam and the phase transitions generated by a semifinished powder product, crystallization, and the concomitant effects in the growing element is the key to gaining insight into the microstructure and the efficient properties of the obtained material and the prevention of residual deformation (shrinkage) of the item. Currently, the main causes of unpredictable production defects are deviations of the shape of the final item from the preset geometry and high-amplitude residual stresses, which can initiate destruction of the item under loads significantly lower than those calculated, as well as the occurrence of the microscopic defects (pores, layer interfaces, etc.) are. The development of mathematical models that, on the one hand, are sufficiently accurate to predict the listed phenomena and, on the other hand, allow practical implementation in engineering calculations is the basis for the further development of the laser-melting and fusion of metal materials. At the same time, analysis of the current state of the problem shows that development of efficient numerical methods providing acceptable computational costs while maintaining accuracy is the key element in the practical implementation of the models. A method based on multiscale, interconnected modeling of the mechanical and the thermal state of the growing body—at the local level in the melt pool domain, at the intermediate level in the vicinity of the melt pool and the adjacent layers, and at the level of the entire product as a whole—seems to be efficient; here, the computing process at the global level can be based on a combination of the finite-element method (indisputable in practice) and analytical calculations providing local refinement of the solution.
关键词： numerical methods,heat-transfer simulation,microstructure,residual deformation,mathematical models,fusion,thermal processes,selective laser melting,additive technologies
更新于2025-09-23 15:19:57
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A numerical study on a photovoltaic thermal system integrated with a thermoelectric generator module
摘要： In this work, a three-dimensional numerical model is developed to investigate the performance of a photovoltaic thermal system integrated with a thermoelectric generator module (PVT/TE). Furthermore, the effects of various operating parameters such as solar radiation, coolant mass flow rate, and inlet and ambient temperatures on the performance of both the PVT and PVT/TE systems are investigated and compared. Based on the obtained results, the electrical efficiency of the PVT/TE system, when exposed to solar radiation of 600 and 1000 W/m2, is 6.23% and 10.41% higher than that of the PVT system, respectively. Besides, the electrical efficiency of the PVT and PVT/TE by increasing the inlet fluid temperature from 26 oC to 34 oC, reduces by 2.58% and 4.56%, respectively. Furthermore, by increasing the ambient temperature from 26 oC to 34 oC, the electrical efficiency of the PVT reduces by 1.43%, the electrical efficiency of the PVT/TE increases by 0.82%. Based on the simulation results, the electrical efficiency of the PVT/TE system is much higher than that of the PVT system, while the PVT system benefits from higher thermal efficiency in comparison to the PVT/TE system.
关键词： Numerical simulation,Electrical efficiency,Thermal efficiency,Thermoelectric generator module (TE),Photovoltaic thermal system (PVT)
更新于2025-09-23 15:19:57
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Robust code-based modeling approach for advanced photovoltaics of the future
摘要： Modeling and simulation of photovoltaics help to reduce development costs, design turnaround time and facilitates better techno-economic decisions. However, there is a current need to generate new theories, algorithms, applications and software in order to increase the contribution of solar energy to the global energy supply. For future advancements in the field of photovoltaics, robust techniques for PV modeling, simulation, visualisation and design are required to overcome the limitations of the current approaches. This study proposes the Code-Based Modeling (CBM) approach as a potent approach to facilitate the study of PV technologies. Experimental data were synthesised and used for coding and training of the code-based (CB) model; followed by a validation of the trained model using commercial PV modules. Results clearly show that the model can repeatedly and reliably predict the short circuit current, maximum power point, open circuit voltage with 0%, < 2% and < 10% deviations, respectively. Furthermore, instances of the applicability of the CBM approach in the study of the thermodynamics of PV, solar cell materials characterisation, PV systems design and power monitoring were presented. Above all, CBM approach accepts user-defined functions and therefore presents new opportunities for scientists and engineers to advance model-based investigations of the photovoltaics beyond the current state-of-the-art.
关键词： Code-based modeling,Block-based modeling,Photovoltaic tools,Simulation,Photovoltaic systems
更新于2025-09-23 15:19:57
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Investigation of Light-sail and Hole-boring Radiation Pressure Accelerations upon the Interaction of Ultra-intense Laser Pulses with Thin Targets
摘要： The radiation pressure acceleration (RPA) scheme with a circularly polarized laser pulse is well-known to provide an efficient generation of intense, energetic quasi-monochromatic ion beams. Depending on the thickness of targets, the RPA appears in two distinct modes: the light-sail (LS) RPA, which develops in ultrathin targets, and the hole-boring (HB) RPA, which develops in relatively thick targets. In this work, we investigated the ion acceleration dynamics of the LS-RPA and the HB-RPA through a fully relativistic particle-in-cell (PIC) simulation. The transition and competition between LS- and HB-RPA modes are investigated with suitable explanations of a one-dimensional (1D) theoretical model. To check the validity of the 1D results and investigate the multi-dimensional effects, two-dimensional simulations are also carried out. The present work may provide a deeper understanding of RPA and useful guidelines for generating high-quality and high-fluence ion beams.
关键词： Ion acceleration,Radiation pressure acceleration,Laser-plasma interaction,Particle-in-cell simulation
更新于2025-09-23 15:19:57
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Controlled Phase Gate Protocol for Neutral Atoms via Off-Resonant Modulated Driving
摘要： Neutral-atom arrays serve as an ideal platform to study quantum simulation and quantum logic gates, where intense efforts have been devoted to improving the fidelity of two-qubit gates. We report our recent findings in constructing a different type of two-qubit controlled phase gate protocol with neutral atoms enabled by the Rydberg blockade, which aims at both robustness and high fidelity. It relies upon a modulated driving pulse with a specially tailored smooth waveform to gain appropriate phase accumulations for quantum gates. The major features include finishing a gate operation within a single pulse, not necessarily requiring individual site addressing, not being sensitive to the exact value of the blockade shift, and suppressing the population leakage error and rotation error. Building upon this progress, we further develop an upgrade in the form of dual-pulse off-resonant modulated driving with the major distinct feature of Doppler insensitivity, in order to address the challenge to the fidelity of two-qubit gates caused by residual thermal motion of the cold atoms. In principle, the gate fidelity remains reasonably high over a relatively significant velocity range of the qubit atoms. Moreover, we anticipate that this will inspire future improvements in gate protocols for other types of qubit platforms, and the strategies used here may find applications in the area of quantum optimal control.
关键词： Doppler insensitivity,controlled phase gate,quantum logic gates,neutral-atom arrays,Rydberg blockade,quantum simulation
更新于2025-09-23 15:19:57
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Numerical study on the laser ablative Rayleigha??Taylor instability
摘要： The laser ablative Rayleigh–Taylor instability plays an important role in the ignition of inertial re?nement fusion. An accurate simulation of this process is important to control the growth of ?ow instability during the implosion. In this paper, taking the simulations of the hydrodynamics, the laser energy deposition and the electronic thermal conductivity into consideration, a massively parallel laser ablative Rayleigh–Taylor instability code based on Euler method is developed. Some open source codes are used to improve the code development ef?ciency. The accuracy of the hydrodynamics simulation is tested by an analytical theory about the weakly nonlinear Rayleigh–Taylor instability with double interfaces. The benchmark of an one dimensional heat conductivity is used to test the accuracy of the thermal conductivity simulation. The laser ablative plane target and the laser ablative Rayleigh–Taylor instability are used to test the reliability of the code on the simulation of the whole laser ablative process. It is shown that the con?dence of our numerical simulation code is high and the code framework we designed is effective. It can be a basis on studying the problems about the laser ablative instability in inertial re?nement fusion.
关键词： Rayleigh–Taylor instability,Numerical simulation,Inertial con?nement fusion,Laser ablation
更新于2025-09-23 15:19:57