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A method for diagnosing implosion symmetry in inertial confinement fusion (ICF) with wide-angle velocity interferometer system for any reflector (VISAR)was proposed in this study. The method considers the object-image relationship of the wide-angle VISAR, characteristics of the fringe pattern, and the symmetry theory; the fringe pattern must be continuous in space to apply this method. Hydrodynamic calculations showed that the radiation-temperature distribution on the surface of capsule was spatially continuous, indirectly proving the applicability of the method. The evolution of P2 asymmetry at different positions of the capsule was examined through an eight-beam laser indirect-drive experiment at a 10 kJ-level laser facility, proving the feasibility of the method. The application of wide-angle VISAR for the diagnosis of implosion symmetry in ICF was more accurate and intuitive and demonstrated high spatiotemporal resolution and wide detection range. This method can provide reference data for the micro-mechanism study of hydrodynamic instability and radiation-driven asymmetry, as well as support for optimizing the implosion compression process to achieve efficient and stable ignition.

The symmetry diagnosis of the implosion process can reflect the compression evolution, as well as laser ablation symmetry and hydrodynamic instability, which is a significant research topic for improving implosion performance in inertial confinement fusion (ICF). The wide-angle velocity interferometer system for any reflector (VISAR) has the ability to diagnose three-dimensional implosion compression. However, the preheating phenomenon limits the applicability of wide-angle VISAR. This work developed a radiation hydrodynamics simulation model of wide-angle VISAR preheating to investigate the effect of various parameters on diagnostic system performance. It specifically investigates the impact of ablator layer thickness, shielding thickness, laser energy, and M-band x-ray radiation fractions on the wide-angle VISAR. The results indicate that excessively thin ablator and shielding layers result in the preheating of the ellipsoidal mirror. The increased peak radiation temperature shifts the energy spectrum into the M-band region, causing the ellipsoidal mirror to be preheated and melted, and the wide-angle VISAR to lose its diagnostic capability. Indirect drive implosion experiments were carried out to verify the simulation results. When the peak radiation temperature is 160 eV, with insufficient thickness of the ablator layer and the shielding layer, the shock wave enters the CH layer for 0.50 ns, and the ellipsoidal Al mirror will be completely melted. However, the current wide-angle VISAR can obtain velocity information at lower drive energy. In the future work, it is planned to shield the preheating effects, which will be helpful to promote the application of wide-angle VISAR for 3D symmetry diagnostics under high radiation temperature conditions and ultimately provide an important diagnostic tool for ICF. [ABSTRACT FROM AUTHOR]

AbstractThe stochastic processes are a natural choice for describing the randomness in degradation processes caused by inherent randomness and environmental factors. This article proposes a new modified skew-normal distribution to capture measurement uncertainty, and then establishes a stochastic process-based degradation modeling framework, in which both degradation increments and measurement errors do not follow the Gaussian distributions. Taking the IG process as an example, the basic reliability indicators and the alarm probabilities caused by measurement errors are derived. In addition, a multi-stage parameter estimation algorithm based on moderate particle sizes and comparative tolerances is developed for this stochastic process-based degradation model under dual non-Gaussian assumptions. Finally, the effectiveness and advantages of the proposed model along with the parameter estimation algorithm are demonstrated by a simulation study and a case application, and it is particularly pointed out that the relative size of measurement errors has a significant impact on the precision of degradation reliability assessment. [ABSTRACT FROM AUTHOR]

Objective To compare the safety and efficacy of fluoroscopic guidance (FG), total ultrasonographic guidance (USG), and combined ultrasonographic and fluoroscopic guidance (CG) for percutaneous renal access in mini-percutaneous nephrolithotomy (mini-PCNL). Patients and methods The present study was conducted between July 2014 and May 2015 as a prospective randomised trial at the First Affiliated Hospital of Guangzhou Medical University. In all, 450 consecutive patients with renal stones of >2 cm were randomised to undergo FG, USG, or CG mini-PCNL (150 patients for each group). The primary endpoints were the stone-free rate (SFR) and blood loss (haemoglobin decrease during the operation and transfusion rate). Secondary endpoints included access failure rate, operating time, and complications. S.T.O.N.E. score was used to document the complexity of the renal stones. The study was registered at (NCT02266381). Results The three groups had similar baseline characteristics. With S.T.O.N.E. scores of 5-6 or 9-13, the SFRs were comparable between the three groups. For S.T.O.N.E. scores of 7-8, FG and CG achieved significantly better SFRs than USG (one-session SFR 85.1% vs 88.5% vs 66.7%, P = 0.006; overall SFR at 3 months postoperatively 89.4% vs 90.2% vs 69.8%, P = 0.002). Multiple-tracts mini-PCNL was used more frequently in the FG and CG groups than in the USG group (20.7% vs 17.1% vs 9.5%, P = 0.028). The mean total radiation exposure time was significantly greater for FG than for CG (47.5 vs 17.9 s, P < 0.001). The USG had zero radiation exposure. There was no significant difference in the haemoglobin decrease, transfusion rate, access failure rate, operating time, nephrostomy drainage time, and hospital stay among the groups. The overall operative complication rates using the Clavien-Dindo grading system were similar between the groups. Conclusions Mini-PCNL under USG is as safe and effective as FG or CG in the treatment of simple kidney stones (S.T.O.N.E. scores 5-6) but with no radiation exposure. FG or CG is more effective for patients with S.T.O.N.E. scores of 7-8, where multiple percutaneous tracts may be necessary. [ABSTRACT FROM AUTHOR]