基于C8051F120的可燃气体无线报警系统设计

介绍一种基于Silicon Lab公司的C8051F120单片机设计的可燃气体无线报警仪,并阐述了报警平台的软硬件设计。无线报警系统由报警器和报警平台两部分组成,两者通过射频芯片SI4432实现数据的无线传输,并由报警平台上的GR64模块通过GSM网络以SMS方式实现远程报警功能。测试结果表明:该系统性能稳定、抗干扰能力强,具有很高的应用价值。     

数字电视电子节目指南EPG的实现方式

从介绍数字电视电子节目指南EPG的功用和构成入手,引出了DVB系统中的业务信息SI和节目描述信息PSI,并详细介绍了SI和PSI的信息规范,据此讲述了在有线数字电视机顶盒中实现电子节目指南EPG的方式。     

Simulation model of magneto-optic fiber Bragg gratings and its applications in Sagnac interferometers

According to the symmetry of transmission matrix for non-uniform magneto-optic fiber Bragg gratings (MFBGs),the simulation model of the non-uniform MFBGs with bidirectional injection of light has been presented for the Optisystem software.The simulation model is verified by comparing with the Matlab numeric results using the piecewise-uniform MFBG model.As an example,the polarization-dependent loss (PDL) of an MFBG-based Sagnac interferometer (MSI) is analyzed in detail.Simulation results indicate that the magnetic field sensitivity of the MSI system can be improved by optimizing the coupling coefficient of the coupler,and the maximum of peak PDL is up to three times that of the single MFBG structure.The simulation model proposed in the paper is useful for the design of MFBG-based optical information devices.     

一种恶意软件传播的离散概率模型

 复杂网络理论为恶意软件传播的研究提供了新的思路和方法。本文针对恶意软件的实际传播机制,提出一种新的离散概率DP-SI模型, 该模型可适用于任意网络拓扑。同时提出了一种节点信息网络模型方法,为大规模复杂网络及复杂网络上的传播动力学的仿真,以及离散传播动力学模型的建立,提供了有效的研究平台。仿真结果表明本模型比传统模型更接近现实,对恶意软件的控制具有一定指导意义。     

一种面向PVR应用的两级元数据存储检索结构

提出了一种基于音视频数据帧显示时间标签和数字电视电子节目指南的两级元数据存储检索结构。基于该结构设计了用于实现个人视频录像机节目内容快速检索、节目内容的非线性回看、数字电视节目的时移收看方法。     

Low-speed pre-ignition and super-knock in boosted spark-ignition engines: A review

The introduction of downsized, turbocharged Gasoline Direct Injection (GDI) engines in the automotive market has led to a rapid increase in research on Low-speed Pre-ignition (LSPI) and super-knock as abnormal combustion phenomena within the last decade. The former is characterized as an early ignition of the fuel–air mixture, primarily initiated by an oil–fuel droplet or detached deposit. Meanwhile, super-knock is an occasional development from pre-ignition to high intensity knocking through detonation, which is either initiated by a shock wave interacting with a propagating reaction and cylinder surfaces or inside a hotspot with a suitable heat release and reactivity gradient. The phenomenon can be divided into four stages, including LSPI precursor initiation, establishment and propagation of a pre-ignited flame, autoignition of end-gases and development to a detonation. LSPI and super-knock are rare phenomena, difficult to observe optically in engines, and differences in methodologies and setups between steady-state experiments can lead to discrepancies in results. Experimental research has included more detailed approaches using glow plug-equipped engines, constant volume combustion chambers and rapid compression machines. In addition, the improved availability of mechanisms for fuel and lubricant surrogates has allowed researchers to model the oil–fuel interaction at the cylinder walls, evaporation and autoignition of oil–fuel droplets and regimes for different propagation modes of an autoignition reaction wave. This paper presents a comprehensive review of the underlying phenomena behind LSPI and its development to super-knock. Furthermore, it presents the methodology in experimental research and draws conclusions for mitigating strategies based on studies involving fuel, oil and engine parameters. Finally, it discusses the prerequisites for LSPI from oil–fuel droplets and the future needs of research as original equipment manufacturers (OEM) and lubricant industry have already adopted some proven solutions to their products.     

Exergy analysis of a simulation of the sulfuric acid decomposition process of the SI cycle for nuclear hydrogen production

This article details comprehensive energy and exergy analyses of the sulfuric acid decomposition process of the sulfur–iodine (SI) thermochemical cycle for hydrogen production. Energy and exergy efficiencies of the proposed process were evaluated over a variety of reaction temperatures and pressures. At an atmospheric temperature of 25 °C, the calculated values of exergy destruction of the H₂SO₄ decomposer ranged between 157 kJ/mol and 360 kJ/mol over reaction temperatures of 800–1000 °C and pressures between 1 and 50 atm. It was shown that the exergy efficiency of the H₂SO₄ decomposer improved with an increase in reaction temperature, while reaction pressure had a negative effect on exergy efficiency.     

Fragmentation in an Al–7 wt-%Si alloy studied in real time by X-ray synchrotron techniques

Abstract

One mechanism for the formation of equiaxed grains is the detachment of dendrite fragments which is believed to be at the origin of the central equiaxed core region in casting processes. Unfortunately, the dynamics of the fragmentation phenomena cannot be revealed by classical methods. Investigation of a unrefined Al–7 wt-%Si alloy using in situ and real time synchrotron X-radiography and X-ray topography at the European Synchrotron Radiation Facility, has allowed verification of the existence of dendrite fragmentation and of cascade fragmentation during directional solidification, and to study the evolution of the growth and sedimentation of the equiaxed grains formed from these fragments. An examination of the crystallographic misorientation of dendrites as fragmentation is ongoing. These results contribute to the understanding of the characteristics of the columnar to equiaxed transition and to knowledge of the origin of new equiaxed grains in unrefined alloys.     

Fatigue properties of Al–Si casting alloy with cold sprayed Al/SiC coating

Abstract

The fatigue properties of Al–Si alloy cold sprayed Al and Al–SiC composite coatings have been studied. The specimens coated with composites reinforced with a large volume (25%) of fine SiC particles exhibited improved adhesion strength at the interface due to crater formation, and cyclic fatigue lives at room temperature more than three times those of uncoated specimens. In high temperature low cycle fatigue tests at 250°C, the pure Al coatings showed longer fatigue lives than the Al–SiC composite coatings, which is attributed to an increment in ductility at the surface retarding fatigue crack initiation.     

Review of quantum electrical standards and benefits and effects of the implementation of the ‘revised SI’

In the present International System of Units (SI ), the Josephson effect and quantum Hall effect have been utilized for voltage and resistance primary standards, and the electrical current standard has been derived from a combination of the two quantum standards. In 2018, it is planned that the SI will be revised based on the latest measurements results of the Planck constant, elementary charge, Avogadro constant, and Boltzmann constant. The adoption of the ‘Revised SI ’ means we shall finally terminate the traceability of the kilogram tied to an artifact (the international prototype of the kilogram) and start a new traceability of the kilogram to the Planck constant h . In electricity and magnetism metrology, and related precision measurements, the traceability presently based on the ‘conventional values’ of the Josephson constant and the von Klitzing constant is going to be switched to the revised traceability based on the Planck constant and elementary charge. In this article, the foundation of the quantum electrical measurements and how the Revised SI , which is based purely on fundamental physical constants and quantum effects, will bring us a long‐term benefit with negligible impact to industry are detailed. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.