Realtime trigger and localization of bursts are the key functions of GECAM, which is an all-sky gamma-ray monitor launched in Dec 10, 2020. We developed a multifunctional trigger and localization ...software operating on the CPU of the GECAM electronic box (EBOX). This onboard software has the following features: high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation, dedicated localization algorithm optimized for short and long bursts respetively, short time latency of the trigger information which is downlinked throught the BeiDou satellite navigation System (BDS). This paper presents the detailed design and deveopment of this trigger and localization software system of GECAM, including the main functions, general design, workflow and algorithms, as well as the verification and demonstration of this software, including the on-ground trigger tests with simulated gamma-ray bursts made by a dedicated X-ray tube and the in-flight performance to real gamma-ray bursts and magnetar bursts.
Accurately detecting and tracking pedestrians in 3D space is challenging due to large variations in rotations, poses and scales. The situation becomes even worse for dense crowds with severe ...occlusions. However, existing benchmarks either only provide 2D annotations, or have limited 3D annotations with low-density pedestrian distribution, making it difficult to build a reliable pedestrian perception system especially in crowded scenes. To better evaluate pedestrian perception algorithms in crowded scenarios, we introduce a large-scale multimodal dataset,STCrowd. Specifically, in STCrowd, there are a total of 219 K pedestrian instances and 20 persons per frame on average, with various levels of occlusion. We provide synchronized LiDAR point clouds and camera images as well as their corresponding 3D labels and joint IDs. STCrowd can be used for various tasks, including LiDAR-only, image-only, and sensor-fusion based pedestrian detection and tracking. We provide baselines for most of the tasks. In addition, considering the property of sparse global distribution and density-varying local distribution of pedestrians, we further propose a novel method, Density-aware Hierarchical heatmap Aggregation (DHA), to enhance pedestrian perception in crowded scenes. Extensive experiments show that our new method achieves state-of-the-art performance for pedestrian detection on various datasets.
Correlated two-dimensional (2D) layers, like 1T-phases of TaS2, TaSe2 and NbSe2, exhibit rich tunability through varying interlayer couplings, which promotes the understanding of electron-correlation ...in the 2D limit. However, the coupling mechanism is, so far, poorly understood and was tentatively ascribed to interactions among the d_(z^2 ) orbitals of Ta or Nb atoms. Here, we theoretically show that the interlayer hybridization and localization strength of interfacial Se pz orbitals, rather than Nb d_(z^2 ) orbitals, govern the variation of electron-correlated properties upon interlayer sliding or twisting in correlated magnetic 1T-NbSe2 bilayers. Each of the both layers is in a star-of-David (SOD) charge-density-wave phase. Geometric and electronic structures, and magnetic properties of 28 different stacking configurations were examined and analyzed using density-functional-theory calculations. We found that the SOD contains a localized region (Reg-L), in which interlayer Se pz hybridization plays a paramount role in varying the energy levels of the two Hubbard bands. These variations lead to three electronic transitions among four insulating states, which demonstrated the effectiveness of interlayer interactions to modulate correlated magnetic properties in a prototypical correlated magnetic insulator.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is a pair of microsatellites (i.e. GECAM-A and GECAM-B) dedicated to monitoring gamma-ray transients including ...gravitational waves high-energy electromagnetic counterparts, Gamma-ray Bursts, Soft Gamma-ray Repeaters, Solar Flares and Terrestrial Gamma-ray Flashes. Since launch in December 2020, GECAM-B has detected hundreds of astronomical and terrestrial events. For these bursts, localization is the key for burst identification and classification as well as follow-up observations in multi-wavelength. Here, we propose a Bayesian localization method with Poisson data with Gaussian background profile likelihood to localize GECAM bursts based on the burst counts distribution in detectors with different orientations. We demonstrate that this method can work well for all kinds of bursts, especially for extremely short ones. In addition, we propose a new method to estimate the systematic error of localization based on a confidence level test, which can overcome some problems of the existing method in literature. We validate this method by Monte Carlo simulations, and then apply it to a burst sample with accurate location and find that the mean value of the systematic error of GECAM-B localization is \(\sim 2.5^{\circ}\). By considering this systematic error, we can obtain a reliable localization probability map for GECAM bursts. Our methods can be applied to other gamma-ray monitors.
GRB 221009A is the brightest gamma-ray burst ever detected since the discovery of this kind of energetic explosions. However, an accurate measurement of the prompt emission properties of this burst ...is very challenging due to its exceptional brightness. With joint observations of \textit{Insight}-HXMT and GECAM-C, we made an unprecedentedly accurate measurement of the emission during the first \(\sim\)1800 s of GRB 221009A, including its precursor, main emission (ME, which dominates the burst in flux), flaring emission and early afterglow, in the hard X-ray to soft gamma-ray band from \(\sim\) 10 keV to \(\sim\) 6 MeV. Based on the GECAM-C unsaturated data of the ME, we measure a record-breaking isotropic equivalent energy (\(E_{\rm iso}\)) of \(\bf \sim 1.5 \times 10^{55}\) erg, which is about eight times the total rest-mass energy of the Sun. The early afterglow data require a significant jet break between 650 s and 1100 s, most likely at \(\sim950\) s from the afterglow starting time \(T_{AG}\), which corresponds to a jet opening angle of \(\sim {0.7^\circ} \ (\eta_\gamma n)^{1/8}\), where \(n\) is the ambient medium density in units of \(\rm cm^{-3}\) and \(\eta_\gamma\) is the ratio between \(\gamma\)-ray energy and afterglow kinetic energy. The beaming-corrected total \(\gamma\)-ray energy \(E_{\gamma}\) is \(\sim 1.15 \times10^{51} \ (\eta_\gamma n)^{1/4}\) erg, which is typical for long GRBs. These results suggest that this GRB may have a special central engine, which could launch and collimate a very narrowly beamed jet with an ordinary energy budget, leading to exceptionally luminous gamma-ray radiation per unit solid angle. Alternatively, more GRBs might have such a narrow and bright beam, which are missed by an unfavorable viewing angle or have been detected without distance measurement.
Directing at the hybrid high-voltage direct-current (HVDC) system with line commutated converter (LCC) and voltage source converter (VSC), it is of significance to investigate a feasible approach to ...isolate the DC-line fault rapidly and validly. In this study, the performance comparison of employing AC and DC circuit breakers for removing the DC-line fault is conducted. Firstly, the theoretical model and control strategy of the hybrid HVDC system are depicted. Then, the transient characteristics of the fault currents contributed by the LCC and VSC are analyzed. Based on the MATLAB platform, the isolation behaviors of the AC and DC breakers are compared, and herein the peak value of the DC fault currents and the breaking time are selected as the performance indexes. In addition, different action delays of the circuit breakers are taken into consideration. From the simulation results, it is found that using the DC circuit breakers is better than employing the AC breaker to address the DC-line fault, and the isolation time can be controlled within several milliseconds. Finally, some beneficial technical discussions for the fault isolation methods are performed, and it is descried to provide possible improvement directions.
To study the HIV infection risk perception, sexual behavior and condom use among college students who had sexual experiences.
Using data generated from a survey on AIDS related knowledge and risk ...perception and sexual behavior (conducted in a coast city of Zhejiang province in 2003), with a questionnaire involving self-reporting history of sexual experience. Software SPSS 12.0 for windows was used for statistical analysis.
47.0 percent of the 2785 students having had sexual experience did not feel that sexual experience was related to HIV risk while 51.3 percent them considered their sexual behavior was at much low risk. 80.5 percent of the students with sexual experience had ever used condoms, but only 16.0 percent used it consistently. There was no association between risk perception and condom use, but there was association between risk perception and intention for condom use.
The college students having had sexual experience had low level of risk perception on HIV infection and had a high rate of ever con
The early afterglow of a Gamma-ray burst (GRB) can provide critical information on the jet and progenitor of the GRB. The extreme brightness of GRB 221009A allows us to probe its early afterglow in ...unprecedented detail. In this letter, we report comprehensive observation results of the early afterglow of GRB 221009A (from \(T_0\)+660 s to \(T_0\)+1860 s, where \(T_0\) is the \textit{Insight}-HXMT/HE trigger time) in X/\(\gamma\)-ray energy band (from 20 keV to 20 MeV) by \textit{Insight}-HXMT/HE, GECAM-C and \textit{Fermi}/GBM. We find that the spectrum of the early afterglow in 20 keV-20 MeV could be well described by a cutoff power-law with an extra power-law which dominates the low and high energy bands respectively. The cutoff power-law \(E_{\rm peak}\) is \(\sim\) 30 keV and the power-law photon index is \(\sim\) 1.8 throughout the early afterglow phase. By fitting the light curves in different energy bands, we find that a significant achromatic break (from keV to TeV) is required at \(T_0\) + 1246\(^{+27}_{-26}\) s (i.e. 1021 s since the afterglow starting time \(T_{\rm AG}\)=\(T_0\)+225 s), providing compelling evidence of a jet break. Interestingly, both the pre-break and post-break decay slopes vary with energy, and these two slopes become closer in the lower energy band, making the break less identifiable. Intriguingly, the spectrum of the early afterglow experienced a slight hardening before the break and a softening after the break. These results provide new insights into the understanding of this remarkable GRB.
Renal tubulointerstitial fibrosis is the common ending of progressive renal disease. It is worth developing new ways to stop the progress of renal fibrosis. Peroxisome proliferator-activated ...receptor-γ（PPARγ） agonists have been studied to treat diabetic nephropathy, cisplatin-induced acute renal injury, ischemia reperfusion injury and adriamycin nephropathy. In this study, unilateral ureteral obstruction（UUO） was used to establish a different renal fibrosis model. PPARγ agonist pioglitazone was administrated by oral gavage and saline was used as control. At 7th and 14 th day after the operation, mice were sacrificed for fibrosis test and T lymphocytes subsets test. Unexpectedly, through MASSON staining, immunohistochemistry for α-SMA, and Western blotting for α-SMA and PDGFR-β, we found that pioglitazone failed to attenuate renal fibrosis in UUO mice. However, flow cytometry showed that pioglitazone down-regulated Th1 cells, and up-regulated Th2 cells, Th17 cells and Treg cells. But the Th17/Treg ratio had no significant change by pioglitazone. Real-time PCR results showed that TGF-β and MCP-1 had no significant changes, at the same time, CD4＋ T cells associated cytokines were partially regulated by pioglitazone pretreatment. Taken together, pioglitazone failed to suppress renal fibrosis progression caused by UUO.
