一种高可靠双机温备星载计算机的设计与实现

星载计算机对可靠性、实时性和性能有很高的要求,备份技术是提高星载计算机可靠性的有效方法.传统备份技术如冷备份和热备份在提高系统可靠性的同时限制了实时性和性能的提高.提出一种新型的双机温备设计,该设计对主机和从机进行功能上的划分,使主机专注于高效的运行星务程序,而从机则专注于提高系统可靠性.这样可以在保证系统高可靠性的前提下提高实时性,降低备份机制对性能的消耗.首先介绍单机系统的可靠性设计,在此基础上详细阐述了双机系统的设计,包括双机的高速通信、系统的故障检测、双机的切换.最后在工程实践中对方案进行了检验,运行良好.

FlexLogix温备在锅炉蒸汽温度控制系统中的实现

提出了一种FlexLogix控制器实现的锅炉主蒸汽温度控制方案,阐述了FlexLogix温备控制系统的硬件连接及软件设计,并对串级控制和PIDE功能块作了相应的介绍。

冷备和温备系统的可靠度评估方法

研究冷备和温备系统的可靠度评估问题 ,得出了系统可靠度的点估计、矩结构和置信下限 .模拟研究和实际例子说明这种评估方法比较符合实际 .

基于定期不完美主动切换策略的温备系统运行优化模型

对于备份系统的运行,备份单元通常在主用单元发生故障后切换到运行状态,这种切换策略称为普通切换策略.然而,卫星上的一些关键子系统在轨运行时采用了一种新的定期切换策略,针对这两种策略的优劣比较问题,本文基于定期主动切换策略提出了温备份系统运行策略优化模型.首先引入了单元的虚拟寿命理论,再在单元寿命服从任意分布类型下,考虑切换装置可能故障,推导出了温备份系统的可靠度和平均失效时间的解析表达式,然后通过最大化温备系统的平均失效时间来获得优化的定期切换间隔.最后,以威布尔分布下卫星上的陀螺仪温备份子系统为例,说明了模型的适用性和有效性,并对相关参数进行了敏感性分析.

基于FPGA双机容错系统的设计与实现

根据双机容错技术常用方案及特点,结合现场可编程逻门电路(FPGA)程的特性及相关技术,提出并实现了基于FPGA双机容错系统的设计方案.仲裁器机制根据双机工作的监测信号负责完成主备机切换功能.系统在实现过程中,利用FPGA内部时钟信号clk“同步化”异步信号,不但充分发挥了FPGA的内部资源,且避免了因信号毛刺可能产生的电路错误.仿真结果表明,该双机容错机制的设计方案能完成系统所需功能,可靠性较好.

用AT91RM9200构建高可靠嵌入式系统

提出一种基于AT91RM9200处理器的高可靠双机温备解决方案。利用EP1C6、MAX6374设计两个冗余的外部Watchdog监控处理器系统的工作状态,利用AT91RM9200自带的Watchdog作为内部监测机制监控处理器本身的故障;设计并给出了以AT91RM9200为核心的监控机制的具体实现,包括心跳信号的发送和中断服务程序的设计。

贮备系统的可靠性模型

对贮备系统的可靠性模型研究一般只给出了n=1或n=2,个别的给出了n=3的情况,但在实际应用中会经常遇到n>3的情况,又没有一般的可靠性模型通式可利用。本文为解决这方面的困难,给出了贮备系统大部分可靠性模型的通式,对特别复杂的没有通式的可靠性模型也给出了n≥3时的结果。

巧用BRAS的 access-delay 参数实现不中断业务割接

巧用 BRAS 设备的 access-delay 参数配置,利用 BRAS 业务温备方式实现 IP 城域网特定场景 BRAS 设备业务不中 断割接,提升用户感知和维护效率。

Preparation of LaMnO_3 for catalytic combustion of vinyl chloride

LaMnO3was prepared by citrate sol‐gel,coprecipitation,hard template,and hydrothermal methods,respectively,and its catalytic performance for the combustion of vinyl chloride was investigated.N2adsorption‐desorption,X‐ray diffraction(XRD),Raman spectroscopy(Raman),O2temperature programmed desorption(O2‐TPD),H2temperature programmed surface reaction(H2‐TPR)and X‐ray photoelectron spectroscopy(XPS)were used to characterize the physicochemical properties of the LaMnO3samples.The preparation methods had obvious effects on the distribution of oxygen and manganese species on the catalyst surface.The reaction followed the suprafacial mechanism;the activity corresponded with the high amount of Mn4+and adsorbed oxygen species.LaMnO3prepared by the citrate sol‐gel method had the best performance for vinyl chloride combustion with T90of182°C.The optimal activity was attributed to the improved redox capability of Mn4+/Mn3+.More available adsorbed oxygen and Mn4+species on the surface were mainly responsible for the remarkable enhancement of the catalytic activity.

Current role of bloodless liver resection

Liver resections are demanding operations which can have life threatening complications although they are performed by experienced liver surgeons. Recently new technologies are applied in the field of liver surgery, having one goal: safer and easier liver operations. The aim of this article is to address the issue of bloodless liver resection using radiofrequency energy. Radionics, Cool-tipTM System and Tissue Link are some of the devices which are using radiofrequency energy. All information included in this article, refers to these devices in which we have personal experience in our unit of liver surgery. These devices take advantage of its unique combination of radiofrequency current and internal electrode cooling to perform sealing of the small vessels and biliary radicals. Dissection is also feasible with the cool-tip probe. For the purposes of this study patient sex, age, type of disease and type of surgical procedure in association with the duration of parenchymal transection, blood loss, length of hospital stay, morbidity and mortality were analyzed. Cool-tip RF device may provide a unique, simple and rather safe method of bloodless liver resections if used properly. It is indicated mostly in cirrhotic patients with challenging hepatectomies (segment Ⅷ, central resections). The total operative time is eliminated and the average blood loss is significantly decreased. It is important to note that this technique should not be applied near the hilum or the vena cava to avoid damage of these structures.

Effects of Temperature on the Preparation of Magnesium Carbonate Hydrates by Reaction of MgCI2 with Na2CO3

Homogeneous(unseeded)precipitation of magnesium carbonate hydrates by the reaction of MgCl2 with Na2CO3 in supersaturated solutions between 273 and 363K was investigated.The compositions,morphologies and filtration characteristics of the precipitates were studied in detail.The magnesium carbonate hydrates obtained at 313K and in the range of 343-363K showed good morphologies and filtration characteristics.Magnesium oxides(MgO)with high purity(97.6%-99.4%)were obtained by calcining magnesium carbonate hydrates at 1073K.

Temperature Distribution in Ethylene Pyrolyzer

A good understanding of the detailed temperature distribution in the furnace plays an important role in the implementation of operation optimization and design improvement of ethylene pyrolyzer. Numerical simulation of the turbulent flow, combustion and heat transfer was carried out to investigate the temperature distribution in industrial furnace. Inhomogeneities of the flue-gas temperature distribution were observed in X, Y, and Z direction of the furnace from the simulated results. Along the height of the furnace, the average flue-gas temperature increased initially and decreased afterward, and reached its peak at the height of 5 m. The reactor tube skin temperature varied not only along the height of the furnace, but also around the circumference of the tube. The heat flux profiles from the furnace towards the reactor tubes followed the shape of the average flue-gas temperature profile. The heat flux of the inlet tubes was constantly higher than that of the outlet tubes at the same height in the furnace.

Effects of coal rank, Fe_3O_4 amounts and activation temperature on the preparation and characteristics of magnetic activated carbon

Coal-based Magnetic Activated Carbons （CMAC＇s） were prepared from three representative coal samples of various ranks： Baorigele lignite from Inner Mongolia; Datong bitumite from Shanxi province; and Taixi anthracite from Ningxia Hui Auto- nomous Region. Fe3O4 was used as a magnetic additive. A nitrogen-adsorption analyzer was used to determine the specific surface area and pore structure of the resulting activated carbons. The adsorption capacity was assessed by the adsorption of iodine and methylene blue. X-ray diffraction was used to measure the evolution behavior of Fe304 during the preparation process. Magnetic properties were characterized with a vibrating-sample magnetometer. The effect of the activation temperature on the performance of CMAC＇s was also studied. The results show that, compared to Baorigele lignite and Taixi anthracite, the Datong bitumite is more appropriate for the preparation of CMAC＇s with a high specific surface area, an advanced pore structure and suitable magnetic properties. Fe304 can effectively enhance the magnetic properties and control the pore structure by increasing the ratio of meso- pores. An addition of 6.0% Fe304 and an activation temperature of 880 ℃ produced a CMAC having a specific surface area, an iodine adsorption, a methylene blue adsorption and a specific saturation magnetization of 1152.0 m2/g, 1216.7 mg/g, 229.5 mg/g and 4.623 emu/g, respectively. The coal used to prepare this specimen was Datong bitumite.

CO2/CH4 separation using inside coated thin film composite hollow fiber membranes prepared by interfacial polymerization

Carbon dioxide(CO_2) is greenhouse gas which originates primarily as a main combustion product of biogas and landfill gas. To separate this gas, an inside coated thin film composite(TFC) hollow fiber membrane was developed by interfacial polymerization between 1,3–cyclohexanebis–methylamine(CHMA) and trimesoyl chloride(TMC). ATR-FTIR, SEM and AFM were used to characterize the active thin layer formed inside the PSf hollow fiber. The separation behavior of the CHMA-TMC/PSf membrane was scrutinized by studying various effects like feed gas pressure and temperature. Furthermore, the influence of CHMA concentration and TMC concentration on membrane morphology and performance were investigated. As a result, it was found that mutually the CHMA concentration and TMC concentration play key roles in determining membrane morphology and performance. Moreover, the CHMA-TMC/PSf composite membrane showed good CO_2/CH_4 separation performance. For CO_2/CH_4 mixture gas(30/70 by volume) test, the membrane(PD1 prepared by CHMA 1.0% and TMC 0.5%) showed a CO_2 permeance of 25 GPU and the best CO_2/CH_4 selectivity of 28 at stage cut of 0.1. The high CO_2/CH_4 separation performance of CHMA-TMC/PSf thin film composite membrane was mostly accredited to the thin film thickness and the properties of binary amino groups.

China＇s nuclear power under the global 1.5℃ target： Preliminary feasibility study and prospects

This study explores the measures to achieve the global 1.5 ℃ temperature rise target （1.5 ℃ target） by analyzing the feasibility and obstacles of nuclear power in China. The 1.5 ℃target imposes stricter requirements on China＇s nuclear power. Considering the available nuclear power plant sites, nuclear power layout, equipment manufacture ＆ supply, nuclear power plant construction capacity, supportive operation ＆ management talents, investment, cost effectiveness, and public acceptance, the achievement of the development objectives of nuclear power in China considering the 1.5 ℃ Target is difficult. However, it is possible if favorable decisions and policies are made.

Preparation of spherical and dense LiNi_(0.8)Co_(0.2)O_2 lithium-ion battery particles by spray pyrolysis

With citric acid as a polymeric agent layered LiNi0.8Co0.2O2 materials were synthesized by a spray pyrolysis method. The LiNi0.sCo0.2O2 particles were characterized by means of XRD, SEM and TEM. The electrochemical performances of LiNi0.8Co0.2O2 particles were studied in a voltage window of 3.00-4.35 V and at a current density of 30 mA/g. The results show that in the pilot-scale spray pyrolysis process, the morphology of particles is dependent upon the precursor concentration and flux of carrier gas. The initial discharge capacity of the LiNi0.8Co0.2O2particles at 720 ℃ for 12 h is 187.3 mA.h/g, and the capacity remains 96.8% with excellent cycleability after 30 cycles. The LiNi0.8Co0.2O2 samples synthesized under the optimized conditions by the spray pyrolysis method shows a good electrochemical performance.

Preparation of iminodiacetic acid salts from iminodiacetonitrile with additives assisted in subcritical water

Here, the employment of subcritical water as an environmentally benign media has shown a certain potential for the hydrolysis ofiminodiaeetonitrile （IDAN）. Additives （such as NH3.H2O, （NH4）2CO3, K2CO3） were selected to investigate the reactivity ofiminodiacetonitrile in the solutions of these species in the subcritical region for the possibility of preparing iminodiacetic acid （IDA） salts. A series of reactions were performed in a high temperature and pressure batch reactor with temperature ranging from 200 to 260 ℃, time ranging from 4 to 10 min, pressure ranging from 5 to 25 MPa and varying concentration of additives to consider the influence of these parameters on the yield of IDA salts. Reactivity of IDAN was not illustrated with the conversion but with respect to the yield of resultant IDA salts. The results demonstrate that hydrolysis reactivity of IDAN under the examined conditions has shown a remarkable sensitivity to the pH of the system at initial point of the reaction stage, and temperature effect is also obvious. Based on the results, possible reaction pathway and mechanism were proposed.

Effect of promoter MgO on CeO2/Al2O3 oxygen carrier used in partial oxidation of methane to syngas

Promoter MgO on 10% CeO2/Al2O3 oxygen carrier was investigated for direct partial oxidation of methane to syngas in molten salt. The MgO content of 0.5%, 1%, 2%, 3% and 4% on the 10%CeO2/Al2O3 oxygen carriers in experiments were prepared at the temperature of 750℃, respectively. The methane conversion, H2 and CO selectivity was measured on these prepared oxygen carriers at different reaction temperature. The results showed that the 3% MgO on 10%CeO2/Al2O3 had the best activity, and the CH4 conversion and CO selectivity reached 92.58% and 87.64% at 875℃, respectively. The effect of different calcination temperature on 3% MgO as promoter on 10% CeO2/Al2O3 oxygen carrier was investigated. The results of BET indicated that oxygen carrier had the largest surface area at 750℃. When the calcined temperature was too high there would be a negative effect on oxygen carrier activity.

Study on the comparison of the pyrolysis gas release of lignite and its briquette

In this experiment, lignite was refined and processed through binderless briquette preparation process from low-rank coal and became briquette. Then, lignite and its briquette were pyrolysed as materials to compare the nature of their pyrolysis. In this study, the experiment was carried out through a lab tube furnace, at a heating rate of 10 ~C/min, and the gas was analyzed and compared, which was collected at different temperatures. The results show that： in the pyrolysis temperature of 550-850 ℃, the semi-coke yield of briquette is 2%-6% higher than lignite, the tar yield of briquette is 2%-3% higher than lignite and the gas yield of briquette is 4%-9% less than lignite. The time required for complete release of the briquette is about 20 min less than lignite. The components in the pyrolysis gas of lignite and its briquette are the same, and their variation with the pyrolysis temperature is similar.

Preparation of β-Sialon/ZrN bonded corundum composites from zircon by nitridation reaction sintering process

β-Sialon/ZrN bonded corundum composites were synthesized using fused white corundum,alumina micro powder,zircon and carbon black by nitridation reaction sintering process. Phase composition and microstructure of the synthesized composites were investigated by X-ray powder diffraction and scanning electronic microscope,and the formation process of the composites was discussed. The results show that the composites with different compositions can be obtained by controlling the heating temperature and contents of zircon and carbon black. The proper temperature to synthesize the composites is 1773 K.