分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Recently, the observed equation of state for dark energy appears to favor values below $-1$. The tendency implies that the nature of dark energy may be quite different from that of the cosmological constant. In view of the adjustment on the equation of state keeps decreasing, the introduction of the phantom energy seems inevitable. By employing observational constraints from supernovae and from the acoustic scale in which the accuracy of the data has become extraordinary, we apply a phenomenological scenario to be acquainted with the evolution of our universe. The demonstration on the constrained unfolding of the phantom energy shows the model has high consistency with the current observation.
分类: 天文学 >> 天文学 提交时间: 2024-05-10 合作期刊: 《Research in Astronomy and Astrophysics》
摘要: For the ASO-S/HXI payload, the accuracy of the flare reconstruction is reliant on important factors such as the alignment of the dual grating and the precise measurement of observation orientation. To guarantee optimal functionality of the instrument throughout its life cycle, the Solar Aspect System (SAS) is imperative to ensure that measurements are accurate and reliable. This is achieved by capturing the target motion and utilizing a physical model-based inversion algorithm. However, the SAS optical system's inversion model is a typical ill-posed inverse problem due to its optical parameters, which results in small target sampling errors triggering unacceptable shifts in the solution. To enhance inversion accuracy and make it more robust against observation errors, we suggest dividing the inversion operation into two stages based on the SAS spot motion model. First, the as-rigid-as-possible (ARAP) transformation algorithm calculates the relative rotations and an intermediate variable between the substrates. Second, we solve an inversion linear equation for the relative translation of the substrates, the offset of the optical axes, and the observation orientation. To address the ill-posed challenge, the Tikhonov method grounded on the discrepancy criterion and the maximum a posteriori (MAP) method founded on the Bayesian framework are utilized. The simulation results exhibit that the ARAP method achieves a solution with a rotational error of roughly ±35 (1/2-quantile); both regularization techniques are successful in enhancing the stability of the solution, the variance of error in the MAP method is even smaller—it achieves a translational error of approximately ±18 μm (1/2-quantile) in comparison to the Tikhonov method's error of around ±24 μm (1/2-quantile). Furthermore, the SAS practical application data indicates the method's usability in this study. Lastly, this paper discusses the intrinsic interconnections between the regularization methods.
分类: 生物学 >> 神经生物学 分类: 医学、药学 >> 基础医学 提交时间: 2020-03-23
摘要: 在临床实践中,大脑在心脏停跳数分钟后会出现不可逆的损伤,如果30分钟后患者仍未能成功复苏,将被宣布临床死亡。最新研究显示,在心脏停跳后数小时后,猪的大脑细胞功能仍可在体外得到恢复。然而,在离体状态下意识能否恢复尚不清楚。本研究中,我们建立了用于循环停止后大脑体外复苏的常温机械灌注技术。我们发现大脑单独灌注即能维持大脑循环、细胞结构、代谢活动和脑干功能,但不能恢复大脑意识。而在肝脏的支持下,大脑整体的电活动和意识得以恢复,大脑功能至少可以维持22小时。该技术能够使热缺血50分钟的大脑恢复意识。研究结果表明,肝脏辅助下的大脑常温机械灌注技术可以在循环停止较长时间内恢复和维持大脑的意识。