The propagation characteristics of intense femtosecond laser pulses underwater are numerically investigated and modulated by the input energy, lens focal length and beam waist width.The results indicate that, when the system parameters are appropriately selected, the generation of filament can be effectively controlled by the focal length of lens in range of 1 meter to 10 meters underwater, and the filament length reaches the meter scale. With increase of the focal distance (such as f=10 m), the generated plasma filament will oscillate strongly, which is disadvantage to the underwater detection of spectrum. At this time, by increasing the waist width of the beam, the filament can be transmitted more stably at a distant target position underwater. The attenuation effect of the impurities in seawater on pulse energy can be balanced by increasing input power, so as to realize the long-distance transmission of filaments.
Aiming at the diagnosis technology of the horizontal well fracturing effect, a numerical fracture diagnosis method based on the water hammer effect is proposed. Because of the energy dissipation caused by the fracture to the pump shutdown pressure, the traditional water hammer mathematical model is difficultly to apply to the fracture diagnosis of horizontal Wells. In this paper, considering the influence of fracture on the water hammer effect, a mathematical model of water hammer in a horizontal well is established based on the equivalent circuit method, and the model is solved by the characteristics method line. The fracture parameters are deduced based on the characteristics of the water hammer pressure curve, and the variation characteristics of the water hammer pressure curve with different influencing factors are analyzed. The results show that the characteristics of water hammer pressure wave are affected by fracture morphology and construction parameters. and the amplitude and period of hydraulic pressure are changed by fracture volume, displacement and fracturing stage length. The water percussion model is used to carry out historical fitting to the field data, and the coincidence rate of the obtained fracture half-length and height with the microseismic monitoring data is more than 80%, which verifies the accuracy of the model and provideds on idea and method for the fracture parameter evaluation of horizontal wells.
The direct drive laser is the key factor in hybrid drive inertial confinement fusion. Its drive asymmetry has a great influence on the ignition performance of nuclear fusion. Using the same laser power, the impacts of the direct drive laser focal spot size on the ignition performance of a hybrid drive model are studied. It is shown that the size of the laser focal spot is a key parameter to influence the ignition performance of the hybrid drive model. When the size of the laser focal spot is 1 500 μm, the neutron yield of the target is close to the one got by the one dimensional implosion. When the 1 400 μm laser focal spot is used, the neutron yield is 40% of the one got by the one dimensional implosion. However, it is failed to ignite for the 1 200 μm laser focal spot. The high drive asymmetry caused by the small laser focal spot can increase the adiabat in the fuel. The fuel compressibility will decrease when the adiabat is increased, which goes against creating the ignition condition. In this way, the ignition wave is weak. Meanwhile, the high drive asymmetry can lead a high perturbation of the fuel areal density. The perturbation growth of the fuel areal density can make the shell asymmetry grow greatly when the ignition wave is formed. Under the conditions of the weak ignition wave and the high fuel areal density perturbation, the fuel spike with a high density is hard to be ignited. Therefore, the positive feedback between the increase of hotspot temperature and the ignition is restrained. Meanwhile, the fuel spike can decrease the hotspot temperature. The fuel bubble can lead the hotspot expand rapidly. All these factors will make the ignition performance decrease when a small laser focal spot is used.
We report new progress in hybrid-drive (HD) ignition target design with a high-adiabat (>3.0) and high-velocity (>400 km·s-1). First, two-shock indirect-drive (ID) radiation temperature with lower peak 200 eV ablates and pre-compresses the capsule. Later, direct-drive lasers of power 340 TW in flat-top pulse are absorbed near critical surface, combined with the radiation to drive the implosions. The "snowplow" effect in the HD heaps low ID corona density into a high HD plasma density at the radiation ablation front where maximal HD pressure reaches over 500 Mbar. Such high pressure further drives capsule imploding with peak velocity about 424.5 km·s-1 and fuel aidabat about 3.4, and the high-velocity and high-adiabat lower the hotspot pressure required to ignition lower to about 200 Gbar at a low convergent ratio 23 to suppress hydrodynamic instabilities. 2D simulation also predicts the growth factor (GF) at hotspot is very small < 10, beneficial for a robust hotspot and further burn.
The stimulated Brillouin scattering for a bundle beam, which consists of several laser beams, is studied by using the three-dimensional large scale laser plasma interaction code (LAP3D). Several collective scattering, including the ray-retracing, shared ion acoustic wave, shared scattering light, are observed. These phenomena are explained in different parameters.
A deep reinforcement learning (DRL) based approach is proposed for automatic interpretation of well-testing curves. Based on a deep deterministic policy gradient (DDPG) algorithm, the proposed DRL approach is successfully applied to automatic matching of four different types of well-testing curves. To improve training efficiency, a surrogate well-testing model based on LSTM neural network was established. With episodic training, through interaction with the surrogate model the agent converged finally to an optimal curve matching policy on different well-testing models. It shows that the average relative error of the curve parameter interpretation is 5.51%. Additionally, the proposed DRL approach has a high calculation speed, and the average computing time is 0.27 seconds. In case study applications, the proposed method achieved an average relative error of 4.32% in parameter interpretation, which shows reliability of the method.
A phase-field-crystal model is used to simulate microcrack growth under disturbance strain. Influences of disturbance frequency and temperature on growth behavior and stability of microcrack are discussed. It shows that: ① Fracture mode is affected by temperature of the system under certain conditions. ② Influence of disturbance frequency on crack propagation behavior is affected by temperature of the system. ③ Stability of crack decreases firstly and then increases with the increase of disturbance frequency. The increase of temperature leads to the decrease of crack stability.
As RWCE algorithm is used to optimize heat exchanger networks, the existence of fixed investment cost makes it difficult to produce and retain heat exchanger units with small loads. It makes structures that have not yet fully evolved be eliminated too early. We established a relaxation method of fixed investment cost. The fixed investment cost and the heat exchange of heat exchange unit are processed according to their variation. With heat exchange of heat exchange unit, relaxation strength in optimization process is adjusted in real time to guide and promote the smooth generation and evolution of small load heat exchange unit, so as to enhance structural evolution ability of heat exchange network. The relaxation strategy is applied to 9SP and 15SP examples to verify that the relaxation strategy promotes structural evolution effectively and improves optimization quality. The optimal results (2 903 528 ＄ ·a-1, 5 115 061 ＄ ·a-1) are better than those in literatures.
Development of superintense laser technology has brought historic opportunities and space to expand for the study of interaction between light and matter. The process of nuclear reaction assisted by superintense laser field, especially the influence on cross sections of deuteron-triton fusion reaction, has attracted more and more attention. In this paper, we introduce the rapid development of laser technology and the wide application of superintense laser technology. Then we introduce the cross sections of nuclear fusion reaction and its influencing factors, and review recent progress in the study of light nuclear fusion cross sections in superintense laser field with emphasis on deuteron-triton fusion reaction. At last, we make some prospects for future development in this direction.
An evolutionary algorithm of multi-directional compulsive search strategy for dominant individuals is proposed to evaluate the health of global search of current population by examining individual difference index.When the optimization results stagnate for a long time, the health index becomes worse and the multi-direction forced search strategy of the dominant individual is started to expand the search direction of the dominant individual near the local optimal solution region, so as to ensure the global search ability of the algorithm.The strategy was applied to 15SP and 20SP calculation examples and results were compared with optimal results in the literature.They are decreased by 1.09% and 0.83%, respectively.It in dicates that the dominant individual multi-directional compulsive search strategy exerts fully the evolutionary potential of the dominant individual and improves the optimization efficiency of the algorithm.
