Constraints on jet formation mechanisms with the most energetic giant outbursts in MS 0735+7421

Giant X-ray cavities lie in some active galactic nuclei (AGNs) locating in central galaxies of clusters, most of these cavities are thought to be inflated by jets of AGNs. The jets can be either powered by rotating black holes or the accretion disks surrounding black holes, or both. In this work, we choose the most energetic cavity, MS 0735+7421, with stored energy ~ 10^62 erg, to constrain the jet formation mechanisms and the evolution of the central massive black hole in this source. The bolometric luminosity of the AGN in this cavity is ~ 10^(-5) L_Edd, however, the mean power of the jet required to inflate the cavity is estimated as ~ 0.02 L_Edd, which implies that the source has experienced strong outbursts previously. During outbursts, the jet power and the mass accretion rate should be significantly higher than its present values. We construct an accretion disk model, in which the angular momentum and energy carried away by jets is properly included, to calculate the spin and mass evolution of the massive black hole. In our calculations, different jet formation mechanisms are employed, and we find that the jets generated with the Blandford-Znajek (BZ) mechanism are unable to produce the giant cavity with ~ 10^62 erg in this source. Only the jets accelerated with the combination of the Blandford-Payne (BP) and BZ mechanisms can successfully inflate such a giant cavity, if the magnetic pressure is close to equipartition with the total (radiation+gas) pressure of the accretion disk. For dynamo generated magnetic field in the disk, such an energetic giant cavity can be inflated by the magnetically driven jets only if the initial black hole spin parameter a_0 > 0.95. Our calculations show that the final spin parameter a of the black hole is always ~ 0:9 - 0.998 for all the computational examples which can provide sufficient energy for the cavity of MS 0735+7421.Comment: 25 pages, 8 figures, accepted by Ap

A strong negative correlation between radio loudness RUVR_{\rm UV} and optical-to-X-ray spectral index αox\alpha_{\rm ox} in low-luminosity AGNs

It has been argued for years that the accretion mode changes from bright active galactic nuclei (AGNs) to low-luminosity AGNs (LLAGNs) at a rough dividing point of bolometric Eddington ratio $\lambda \sim 10^{-2}$. In this work, we strengthen this scenario through investigation of the relationship between the radio loudness $R_{\rm UV}$ and the optical-to-X-ray spectral index $\alpha_{\rm ox}$ in LLAGNs with $10^{-6} \lesssim \lambda \lesssim 10^{-3}$. We compile from literature a sample of 32 LLAGNs, consisting 18 LINERs and 14 low Eddington ratio Seyfert galaxies, and observe a strong negative $R_{\rm UV}$--$\alpha_{\rm ox}$ relationship, with large scatter in both $R_{\rm UV}$ and $\alpha_{\rm ox}$. We further demonstrate that this negative correlation, and the additional two negative relationships reported in literature ($R_{\rm UV}$--$\lambda$ and $\alpha_{\rm ox}$--$\lambda$ correlations), can be understood consistently and comprehensively under the truncated accretion--jet model, the model that has been applied successfully applied to LLAGNs. We argue that the scatter in the observations are (mainly) due to the spread in the viscosity parameter $\alpha$ of a hot accretion flow, a parameter that potentially can serve as a diagnose of the strength and/or configuration of magnetic fields in accretion flows.Comment: 8 pages, 3 figures, 2 tables. Accepted by MNRA

Pseudo Mask Augmented Object Detection

In this work, we present a novel and effective framework to facilitate object detection with the instance-level segmentation information that is only supervised by bounding box annotation. Starting from the joint object detection and instance segmentation network, we propose to recursively estimate the pseudo ground-truth object masks from the instance-level object segmentation network training, and then enhance the detection network with top-down segmentation feedbacks. The pseudo ground truth mask and network parameters are optimized alternatively to mutually benefit each other. To obtain the promising pseudo masks in each iteration, we embed a graphical inference that incorporates the low-level image appearance consistency and the bounding box annotations to refine the segmentation masks predicted by the segmentation network. Our approach progressively improves the object detection performance by incorporating the detailed pixel-wise information learned from the weakly-supervised segmentation network. Extensive evaluation on the detection task in PASCAL VOC 2007 and 2012 [12] verifies that the proposed approach is effective

A physics-based pi pre-layout tool for PCB PDN design

With increasingly stringent requirements for lower voltage supply, and higher density in PCB PDN design, now integrity (PI) is an increasingly important aspect that must be considered. A pre-layout tool based on the Cavity Model and Boundary Element Method is built to automatically achieve a specified target impedance for a multi-layered Printed Circuit Board (PCB) Power Distribution Network (PDN) design with a minimal number of decoupling capacitors. The pre-work about the post-layout design and analysis is proposed and the guidelines for creating a decoupling capacitors network with better performance has been built. With limit inputs, physical limitations for the minimal impedance that can be achieved in PDN system are calculated first to determine if a design is physically realizable and provide feedback to the user. The decoupling capacitor location will be determined by physics. Then a special decoupling capacitor selection algorithm through poles and zeros is utilized to determine which decoupling capacitor from a library should be added. Finally, the target impedance could be achieved using the minimum number of decoupling capacitors. Genetic algorithm is utilized to verify the performance and time cost of the new designed algorithm and several industry designs are used to verify the calculation result. The process is quite time-saving and convenient, and allows the user to do design discovery quickly, and determine the limiting factors under different conditions. --Abstract, page iii

Legal aspects of privately financed infrastructure projects (PFIPs) in China—the case for international standards

This thesis discusses the reform and improvement of Chinese legislation on Privately Financed Infrastructure Projects (PFIPs), to develop the PFIP model in China, under the protection of Chinese laws, so that its implementation in China may reach international standards. Existing Chinese laws are found to be insufficient in reducing risks to PFIPs because of certain shortcomings. Therefore, it is necessary to reform and improve Chinese legislation on PFIPs, to prevent their failure. The Legislative Guide and Model Provisions drafted by UNCITRAL are treated as the international standards to guide Chinese legislation reform on PFIPs. Other countries’ laws on PFIPs provide supplementary reference. This thesis addresses its aim in four steps: First, the current Chinese legislative and institutional framework on PFIPs is reviewed, with discussion on establishing a more appropriate legislative and institutional framework, to facilitate the development of PFIPs in China through the principles of transparency, fairness, long-term sustainability and the elimination of undesirable restrictions. Second, Chinese laws on the concessioner selection procedure in PFIPs are reviewed, with discussion on possible improvements to the laws to achieve international standards of fairness and transparency. Third, current Chinese laws and policies which affect the various contracts involved in PFIPs are reviewed, with discussion on these may be improved to achieve international standards. Fourth, the PFIP dispute settlements that may be used in China are reviewed, with discussion on the necessity to remove certain undesirable restrictions in relevant Chinese laws. Following the rapid rise in the practical use of PFIPs in China, this thesis offers a strong theoretical basis for suggesting a reform of Chinese legislation on PFIPs. It also provides a general basis for any national reform of laws on PFIPs in any other countries