Overview to the Hard X-ray Modulation Telescope (Insight-HXMT) Satellite

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results.Comment: 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.0443

Dyeing of Tussah Silk with Reactive Dyes: Dye Selection, Dyeing Conditions, Dye Fixation Characteristics, and Comparison with Mulberry Silk

Tussah silk is one of the most widely used wild silks. It is usually dyed with acid dyes, despite the shortcoming of poor wet fastness. Reactive dyeing is a good solution to this problem. In our work, sulfatoethylsulfone (SES), sulfatoethylsulfone/monochlorotriazine (SES/MCT), monochlorotriazine (MCT), and bis(monochlorotriazine) (Bis(MCT)) dyes were used to dye tussah silk. All of these dyes showed lower exhaustion and fixation on tussah silk than on mulberry silk under alkaline conditions. Among them, SES dyes were more applicable, with a fixation of 70–85% (at 4%owf dye) at 90 °C when using sodium bicarbonate as an alkali. SES dyes also showed a rapid fixation speed. The dyeing of tussah silk required lower sodium bicarbonate dosage, the use of more neutral electrolytes, and a higher dye quantity to achieve deep effects compared to mulberry silk. Dyed tussah silk displayed lower apparent color depth and brilliance than dyed mulberry silk. The neutral boiling dyeing of tussah silk with SES dyes exhibited higher exhaustion, higher fixation (82–92% at 4%owf dye), and a slower fixation speed compared with alkaline dyeing. Furthermore, in this dyeing method, SES dyes showed higher and more efficient fixation on tussah silk than on mulberry silk. All dyed tussah silk had excellent color fastness to soaping

Research on an Equivalent Heat Source Model of the AC Arc in the Short Gap of a Copper-Core Cable and a Fire Risk Assessment Method

The magnetohydrodynamics (MHD) model of the alternating current (AC) arc is complex, so a simplified equivalent heat source (EHS) model can be used to replace the complex model in studying the AC arc’s thermal characteristics and cable fire risk. A 2D axisymmetric AC arc MHD simulation model in the short gap of a copper-core cable is established in this paper. The AC arc voltage and current obtained by the model are consistent with experiments. The AC arc’s heat source distribution obtained by the MHD model is fitted to obtain the heat source function Q of the AC arc. Q is divided into 16 independent segmented heat sources, and a correction matrix is constructed to optimize the segmented heat sources. A neural network and a genetic algorithm give the prediction model and the optimal correction matrix of the segmented heat source. The EHS model optimized by the optimal correction matrix can obtain a minimum temperature error of 5.8/4.4/4.2% with the MHD model in different AC arc peak currents 2/4/6 A. The probability of a cable fire is calculated by using AC arc’s optimized EHS model when different numbers of AC arcs are generated randomly in AC half-waves. The EHS model can replace the complex MHD model to study the thermal characteristics of AC arcs and quickly calculate the probability of a cable fire caused by random AC arcs

Spatio-temporal travel patterns of elderly people – A comparative study based on buses usage in Qingdao, China

With the increasing demographic shift towards a larger population of elderly, it is essential for policy makers and planners to have an understanding of travel characteristics of elderly and their difference with younger counterparts. Existing studies emphasize elderly\u27s travel mode, travel frequency, travel distance, travel purpose and affecting factors, however, very few aim at comparing the spatio-temporal characteristics difference between weekday and weekend. In this paper, based on GPS data and Smart Card data of buses in Qingdao, the two cohorts\u27 basic spatio-temporal travel patterns in aspects of travel distance, travel frequency and travel start time in weekday and weekend are compared. In addition, directed weighted networks of elderly\u27s trips and younger people\u27s trips in weekday and weekend are constructed for analyzing spatial characteristics. Results show that although the number of elderly experiences a reduction on weekend their travel frequency and travel distance show growth on weekend. In contrast with younger people, larger geospatial expansion of elderly\u27s travel on weekend is observed. Elderly are found to prefer traveling in areas with high elderly people\u27s residential density. Our study provides a deeper and nuanced understanding of elderly\u27s spatio-temporal travel characteristics difference between weekday and weekend, so as to support better traffic policy making and the promotion on age-friendly public transport service

Numerical investigations of AC arcs’ thermal characteristics in the short gap of copper-cored wires

Abstract Excessive alternating current (AC) arcs generated in electric systems will accumulate heat and easily cause fire. This paper studies the thermal characteristics of different numbers of AC arc plasma generated in a short gap of copper-cored wires in the air. The number of AC arcs is controlled in the AC arc experiment and an infrared thermal imager measures the temperature change at the specified position. Based on magnetohydrodynamics (MHD), a two-dimensional axisymmetric AC arc discharge numerical simulation model is established. The volt-ampere characteristic of the AC arc is used to solve the MHD simulation model to obtain the same 'zero current' characteristics as the real AC arc in the experiment. A large amount of heat accumulates in the electrode gaps when the arc generation, and then the heat dissipates in the 'zero current' stage. The continuously generated arc makes the temperature higher. The volume of the space area with a temperature higher than 10,000 K increases with the arc current, but is unrelated to the number of arcs. The volume of the space area with a temperature higher than 524.15 K and the temperature on the electrode are both positively correlated with the number of AC arcs and arc current. The results of this study can provide a reference for the detection standard of AC arc faults and the prevention of electrical fire

Laboratory simulation of dissolved oxygen reduction and ammonia nitrogen generation in the decay stage of harmful algae bloom

To evaluate how the decay of bloom-forming algae affect the coastal dissolved oxygen, a laboratory simulation was conducted in terms of three typical harmful algae, Alexandrium catenella, Prorocentrum donghaiense, and Skeletonema costatum. Algae of same biomass (55 mu g/mL) were conducted in lightproof columns, and the cell density, dissolved oxygen (DO), and ammonia nitrogen of different layers were monitored at certain time series. Results show that the decomposition of algae significantly decreased the DO, and increased the ammonia nitrogen in all layers; and significant deference between different species was observed. The A. catenella treatment showed the lowest DO (average concentration of 3.4 mg/L) and the highest ammonia nitrogen (average concentration of 0.98 mg/L) at the end of test, followed by P. donghaiense; and the S. costatum showed relatively high DO and low ammonia nitrogen due to slow decay rate. Results indicate that decomposition of harmful bloom algae, especially dinoflagellate, would cause significantly DO depletion and toxic ammonia nitrogen increase, which will detrimentally affect both pelagic and benthic ecosystem

A pine needle-like superhydrophobic Zn/ZnO coating with excellent mechanochemical robustness and corrosion resistance

The superhydrophobic Zn-based coating with hierarchical structure has good prospects in metal anticorrosion. However, the practical application of superhydrophobic coating is still limited by the poor mechanical stability of micro/nano hierarchical structure. Herein, a robust superhydrophobic Zn/ZnO coating with pine needle-like structure and superior corrosion resistance was design and constructed. The micro-scale polyhedral Zn was fabricated on steel followed by the deposition of radially aligned ZnO nanorods, forming a novel pine needle-like hierarchical structure, which was finally modified by stearic acid. Notably, the pine needle-like structured Zn/ZnO (Zn/ZnO-3) coating exhibits excellent superhydrophobicity with contact angle of 166.8 ± 1.4° and sliding angle of 2.6 ± 0.5°. What's more, Zn/ZnO-3 coating maintains superhydrophobicity after suffering from strong acid/alkali, tape peeling, water drop impact and sandpaper abrasion tests. Compared with carbon steel and hydrophobic Zn coating, the corrosion current density of superhydrophobic Zn/ZnO-3 coating is decreased by approximately 4 and 3 orders of magnitude, respectively. The superior mechanochemical stability and anti-corrosion performance of superhydrophobic Zn/ZnO-3 coating is ascribed to its pine needle-like structure. Overall, this work provides a novel strategy to design hierarchical structured superhydrophobic surfaces with excellent mechanochemical stability and corrosion resistance, holding great prospects in metallic corrosion protection

Hyperspectral Unmixing with Bandwise Generalized Bilinear Model

Generalized bilinear model (GBM) has received extensive attention in the field of hyperspectral nonlinear unmixing. Traditional GBM unmixing methods are usually assumed to be degraded only by additive white Gaussian noise (AWGN), and the intensity of AWGN in each band of hyperspectral image (HSI) is assumed to be the same. However, the real HSIs are usually degraded by mixture of various kinds of noise, which include Gaussian noise, impulse noise, dead pixels or lines, stripes, and so on. Besides, the intensity of AWGN is usually different for each band of HSI. To address the above mentioned issues, we propose a novel nonlinear unmixing method based on the bandwise generalized bilinear model (NU-BGBM), which can be adapted to the presence of complex mixed noise in real HSI. Besides, the alternative direction method of multipliers (ADMM) is adopted to solve the proposed NU-BGBM. Finally, extensive experiments are conducted to demonstrate the effectiveness of the proposed NU-BGBM compared with some other state-of-the-art unmixing methods.Applied Science, Faculty ofNon UBCElectrical and Computer Engineering, Department ofReviewedFacult