区域控制器的安全需求建模与自动验证

轨道交通区域控制器（ZC）是我国轨道交通信号系统选型的主流制式——基于通信的列车控制系统（CBTC）的核心子系统，其突出的安全性使得安全需求的形式化验证成为一个非常重要的问题.但是ZC自身的复杂性以及领域知识的繁杂难以掌握，使得形式化方法很难应用到安全需求的验证中去.针对这些问题，提出一种安全需求的自动验证方法，使用半形式化的问题框架方法（PF）来建模和分解安全需求，根据需求模型自动生成安全需求的验证模型和验证性质，在此基础上自动生成验证模型的Scade语言实现，并通过Design Verifier验证器对需求进行组合验证.最后，使用了某个实际案例ZC的一个子问题CAL_EOA进行了研究，实验结果证明了该方法的可行性与有效性，它能自动地将安全需求模型进行组合验证，改善了验证的效率.     

Index decomposition analysis for comparing emission scenarios: Applications and challenges

As global action on climate change gathers momentum, an area of interest is what the world's greenhouse gas emission trajectory will be in the future and whether it can meet the emission targets set forth. To address these questions, emission scenarios which range from business-as-usual to deep decarbonization scenarios have been developed by researchers using different assessment models. An understanding of the sources of variations across the range of these emission trajectories is of interest for discussions, debates and policy planning. However, since these models often have different structures and input variables, comparisons of the results are not straightforward. In this regard, index decomposition analysis (IDA) has emerged as a tool to facilitate comparisons in a harmonized way. It allows differences in emissions over time or between models to be broken down based on a set of accepted driving factors. This paper reviews the literature and summarizes the features and challenges. A multi-level scenario decomposition framework is proposed to address the challenges which include how to quantify differences arising from the energy transformation sector, the adoption of renewable energy, carbon capture and storage, and bio-energy carbon capture and storage technologies. A case study and guidelines for implementing the framework are presented.     

掺铒单模光纤飞秒脉冲激光器和放大器

为了获得一种被动锁模掺铒光纤振荡器及功率放大器，数值模拟出超短脉冲在光纤中的传输和演化过程，并基于此搭建了一种被动锁模掺铒光纤飞秒振荡器及功率放大器。实验获得了中心波长1560 nm、重复频率100 MHz、输出功率30 mW、脉冲宽度85 fs超短脉冲。通过采用PPLN晶体进行倍频，进一步获得了输出功率5 mW，中心波长780 nm的飞秒脉冲。该光纤激光器为全保偏光纤结构，具有体积小巧、可靠性高、稳定性好的特点。     

MWCNTs-GONRs/Co3O4 electrode with needle-like arrays for outstanding supercapacitors

Multiwalled carbon nanotubes-graphene oxide nanoribbons (MWCNTs-GONRs) exhibit high specific surface area and good electroconductivity because of their unique three-dimensional cross-linking structure with the properties of both CNTs and GONRs. In this study, a hydrothermal method was employed to anchor MWCNTs–GONRs onto a Ni foam (NF) to obtain a precursor substrate. Subsequently, Co₃O₄ arrays were grown on the NF substrate to synthesize a MWCNTs–GONR/Co₃O₄ electrode. The electrode showed a capacitance of 846.2 F g⁻¹ at 1 A g⁻¹ and a capacitance retention of 90.1% after 3000 cycles. Furthermore, MWCNTs–GONRs/Co₃O₄ and active carbon (AC) were used as the positive and negative electrodes, respectively, to assemble a supercapacitor, which delivered a maximum energy density of 38.23 W h kg⁻¹ and a high power density of 6.80 kW kg⁻¹. In addition, the specific capacitance of the device reached a maximum of 91.5% after 9000 cycles. Thus, the MWCNTs–GONRs/Co₃O₄ electrode showed huge potential for supercapacitor applications.     

Novel core-shell-like Ni-supported hierarchical beta zeolite catalysts on bioethanol steam reforming

Hierarchical-Beta zeolites have been hydrothermally synthesized by adding a new gemini organic surfactant. The used gemini surfactant play the role of a “pore-forming agents” on the mesoscale, on the same time, providing alkaline environment for the system. With this hierarchical Beta zeolite as the core support, we successfully prepared a shell layer of Ni-containing (22 wt%) petal-like core-shell-like catalyst and applied it to bioethanol steam reforming. At the reaction temperature of 350 °C–550 °C, the conversion rate of ethanol and the selectivity of hydrogen were always above 85% and 70%. After reaction of 100 h on stream at 400 °C, there were not obvious inactivation could be observed on NiNPs/OH-MBeta catalyst.     

Characterization and application of a Pt/ZSM-5/SSMF catalyst for hydrocracking of paraffin wax

The microstructured Pt/ZSM-5/SSMF catalysts, for hydrocracking of paraffin wax, have been developed by impregnation method to place Pt onto thin-sheet ZSM-5/SSMF composites obtained by direct growth of ZSM-5 on the sinter-locked stainless steel microfibers (SSMF). The best catalyst is the one with ZSM-5 having a SiO₂/Al₂O₃ weight ratio of 200, delivering ~ 95% conversion with 77.5% selectivity to liquid products or 64.4% selectivity to naphtha at 280 °C. This new approach is capable of increasing the naphtha selectivity with high activity maintenance in comparison with the literature catalysts.     

Dynamic steering of HPC scientific workflows: A survey

The field of scientific workflow management systems has grown significantly as applications start using them successfully. In 2007, several active researchers in scientific workflow developments presented the challenges for the state of the art in workflow technologies at that time. Many issues have been addressed, but one of them named ‘dynamic workflows and user steering’ remains with many open problems despite the contributions presented in the recent years. This article surveys the early and current efforts in this topic and proposes a taxonomy to identify the main concepts related to addressing issues in dynamic steering of high performance computing (HPC) in scientific workflows. The main concepts are related to putting the human-in-the-loop of the workflow lifecycle, involving user support in real-time monitoring, notification, analysis and interference by adapting the workflow execution at runtime.     

非织造过滤介质孔径及截留性能的研究

对应用于液固分离和气固分离的非织造过滤介质的孔径和截留性能测试方法做了研究,指出采用气体流量法进行孔径性能测试,可同时得到非织造过滤介质的最大孔径、平均孔径及孔径分布,全面表征了其孔径性能;并对用于液固和气固分离2个不同领域的非织造过滤介质采用不同的方法做了截留性能测试。同时,对比非织造过滤介质的孔径和截留性能,对二者之间的关联做了探索,为实际工业过程中非织造过滤介质的选用和评价提供了指导。     

Polyaniline-based networks combined with Fe3O4 hollow spheres and carbon balls for excellent electromagnetic wave absorption

Polyaniline (PANI)-based networks combined with Fe₃O₄ hollow spheres and carbon balls (FCP) for improved electromagnetic wave (EMW) absorption were investigated using an easy-to-industrialize solvothermal and physical method. Hollow structure Fe₃O₄ spheres with a lower density than that of the common solid sphere were prepared. As a thin and light magnetic material, Fe₃O₄ hollow spheres generate magnetic loss, carbon balls and PANI networks generate dielectric loss. The magnetic and conductive parts play appropriate roles in achieving complementarity in the EMW absorption. The relatively high specific surface area introduced by PANI networks promotes interfacial polarization and further supports dielectric loss. In conclusion, the above reasons provide multiple attenuation mechanisms. Samples FCP1 (?65.109 dB, at 12.800 GHz, 1.966 mm, from 5.6 to 18.0 GHz) and FCP2 (?61.033 dB, at 8.480 GHz, 3.328 mm, from 4.3 to 18.0 GHz) demonstrated a wide bandwidth, a small thickness, a minimum reflection loss (R_L), and a low loading ratio (25%) in paraffin-based composites. Specifically, their loading ration of 25% is much lower than the loading ratio of conventional materials (usually 50% and above). In addition, the bandwidth is excessively wide, above 12 GHz, possessing good absorption performance in continuous intervals with different thicknesses. Such excellent characteristics have rarely been reported in literature.     

A framework for cloned vehicle detection

Rampant cloned vehicle offenses have caused great damage to transportation management as well as public safety and even the world economy. It necessitates an efficient detection mechanism to identify the vehicles with fake license plates accurately, and further explore the motives through discerning the behaviors of cloned vehicles. The ubiquitous inspection spots that deployed in the city have been collecting moving information of passing vehicles, which opens up a new opportunity for cloned vehicle detection. Existing detection methods cannot detect the cloned vehicle effectively due to that they use the fixed speed threshold. In this paper, we propose a two-phase framework, called CVDF, to detect cloned vehicles and discriminate behavior patterns of vehicles that use the same plate number. In the detection phase, cloned vehicles are identified based on speed thresholds extracted from historical trajectory and behavior abnormality analysis within the local neighborhood. In the behavior analysis phase, consider the traces of vehicles that uses the same license plate will be mixed together, we aim to differentiate the trajectories through matching degreebased clustering and then extract frequent temporal behavior patterns. The experimental results on the real-world data show that CVDF framework has high detection precision and could reveal cloned vehicles’ behavior effectively. Our proposal provides a scientific basis for traffic management authority to solve the crime of cloned vehicle.