路由重分发中次优路径的解决方案

在大型网络中由于采用多种路由协议,必须开启路由器的重分发功能,但是路由重分发可能产生次优路径问题.为解决次优路径问题,通过对利用图形化网络环境模拟器GNS3建立的双向重分发模拟实验网络环境进行研究,分析管理距离值对多协议路由环境下路由选择的影响,设计了两种纠正次优路径的系统解决方案.方案一直接使用distance命令来修改某个协议的管理距离值;方案二利用访问控制列表针对某条路由精确地更改管理距离值.结果表明两种方案都能有效避免路由重分发中次优路径的产生.

路由协议的重分发技术

在整个互联的IP网络中,运行单个路由协议是最理想的,但是,在某些情况下(如公司的合并,多个网络管理员管理的多个部门,使用多个厂商设备的网络环境等),必须使用多个路由协议。运行多个路由协议的网络环境必须使用路由重分发技术。然而,由于路由协议的复杂性,特别是每种路由协议都有自己的metric,在进行路由重分发时,会造成如路由环、慢速的路由收敛或效率低的路由等问题。本文主要阐述了配置路由协议重分发的方法和如何避免因路由协议的重分发而产生路由问题的方法。

路由重分发时需要考虑的问题

讨论了使用重分发时需要考虑的次优路由、路由环路或黑洞问题,提出了解决方案,列举了使用路由管理距离、分发列表和路由映射表的方法来避免出现问题的方案。

多点双向路由重分发潜在问题的研究

路由重分发主要有4种:单点单向重分发、单点双向重分发、多点单向重分发、多点双向重分发。路由重分发能很好地解决网络中不同路由协议间路由相互学习的问题。高职计算机网络技能大赛训练和课堂教学实践中,学生学习路由的多点双向重分发时容易出现的问题主要包括次优路径,路由反馈,环路问题。通过模拟实验与分析,对多点双向路由重分发中出现次优路径和路由反馈问题进行了研究,并提出了常规解决方案。

基于route-map解决路由重分发中次优路由问题

在常规的企业网络中,由于多种因素的影响,需要运行多种不同的路由选择协议,而这就必须要使用路由重分发技术了。本文针对路由重分发过程中路由协议的配置顺序及协议的内在性质不同,导致出现次优路由和路由环路等问题,借助EVE-ng(Emulated Virtual Environment,虚拟仿真环境)模拟器,通过搭建网络环境进行实验,分析了问题产生的原因并给出了两种切实可行的解决方案,其一是通过修改路由管理距离,改变路由的优先级;其二是通过route-map进行路由过滤,从产生次优路由的根源解决问题。

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting(SCS)dust using a sulfating roasting−water leaching process were investigated.The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl.Under the sulfating roasting conditions of the roasting temperature of 250℃ and the sulfuric acid excess coefficient of 1.8,over 74 wt.%of F and 98 wt.%of Cl were volatilized into flue gas.Approximately 98.6 wt.%of Zn and 96.5 wt.%of Cu in the roasting product were dissolved into the leaching solution after the water leaching process,while the leaching efficiencies of Pb and Sn were only 0.12%and 0.22%,respectively.The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.

IS-IS路由泄漏技术及其应用

首先介绍了IS -IS路由协议 ,然后介绍了IS -IS路由泄漏技术的原理 ,对IS -IS路由泄漏的实际应用进行了分析 ,并给出了IS -IS路由泄漏技术的路由器配置实例。

RIP与FSR路由协议分析

对路由协议R IP与FSR进行介绍与比较,阐述了两种协议实现路由重分发的方法,对固定的网络与移动的网络无缝连接提出了希望.

Security Risk Analysis on the Nutrients and Heavy Metals of Biogas Slurry in Agricultural Application

[Objective] This study was to provide scientific basis for the security application of biogas slurry in agriculture through the analysis on the security risk of nu- trients and heavy metals of biogas slurry in agricultural application. [Method] The components of the slurry produced by the anaerobic digestion of straws and manures were systematically analyzed. Different types of biogas slurry with different concentrations were used to conduct the germination test. [Result] The types and proportions of raw materials, and alkali pretreatment affected the compositions and nature of the biogas slurry. Alkali pretreatment could reduce the contents of heavy metals and improved the contents of nitrogen, phosphorous, organic matter and available components. The contents of heavy metals in the biogas slurry were as follows： Cd of 8.76 μg/kg, Cr of 52μg/kg, Pb of 210 μg/kg, Hg of 0.512 μg/kg, As of 140μg/kg, and the contents of Cu and Zn were the highest among the heavy metals, respectively, 279 and 680 μg/kg. All the contents were under the limit standards of the urban wastes for agricultural use. The germination tests of the seeds verified that the slurry with the concentration of lower than 5% could accelerate the germination, while the salt stress could inhibit the growth of seedlings in the slurry. [Conclusion] When the dung are uses as the raw materials for fermentation, appropriate control should be conducted on the feeding proportion or the heavy metals should be pre-removed; when the slurry is used as the liquid fertilizer to apply in the farmland, the dilution or desalting treatment should be conducted at first.

基于BGP和OSPF的VPN业务网接入优化

基于客户的需求和城域网的安全性,以及用户现网机构中心点CE端到电信PE端OSPF路由的局限性,通过将CE和PE之间的OSPF路由协议优化改造为BGP路由协议,使客户的业务网性能得到明显的改善。

直连路由的“慎”用与“巧”用

针对直连路由的复杂使用场景,讨论重分发直连路由代替路由宣告和OSPF与RIP相互重分发,导致直连路由不通两种故障问题及解决办法。

Spatial Distribution and Risk Assessment of Heavy Metals in Paddy Soils of Yongshuyu Irrigation Area from Songhua River Basin,Northeast China

There is an increasing concern for potentially hazardous metals pollution, which can threaten crops production and human health. In this study, the spatial distribution and environmental risks of eight heavy metals in surface soil samples collected from the paddy fields in Yongshuyu irrigation area, Northeast China were investigated. The mean concentrations of Pb, Cr, Cu, Ni, Zn, Cd, Hg and As were 34.6 ± 4.67, 82.8 ± 9.51, 17.3 ± 4.09, 21.2 ± 12.0, 88.6 ± 17.9, 0.18 ± 0.15, 0.22 ± 0.07 and 8.77 ± 2.47 mg/kg, respectively, which were slightly higher than their corresponding background values of Jilin Province, indicating enrichment of these metals in the paddy soils, especially for Ni, Cd and Hg. The spatial distribution of heavy metals was closely correlated with local anthropogenic activities, such as agricultural production, mining and transportation. The hot-spot areas of As and Cd were mainly concentrated in the up-midstream where were associated with agricultural activities. Cr and Cu showed similar spatial distributions with hot-spot areas distributed the whole irrigation area uniformly. Ni was mainly distributed in the downstream where Ni quarries concentrated, while the spatial distribution patterns of Hg was mainly located in the upstream and downstream where the soil was significantly influenced by irrigation and coal mining emission. The spatial distributions of Pb and Zn were mainly concentrated along the highway side. The pollution levels of Yongshuyu irrigation area were estimated through index of geo-accumulation(Igeo), Nemerow integrated pollution index(NIPI) and potential ecological risk index(PERI). The results showed that Cd and Hg were the main pollutants in the study area. Health risk assessment results indicated that children were in higher non-carcinogenic and carcinogenic risks than adults with the carcinogenic metal of As. Ingestion was the main exposure pathway to non-carcinogenic and carcinogenic risk for both adults and children. Principal component analysis(PCA) indicated that Cr and Cu were mainly from parent materials, while Cd and As were mainly affected by agricultural activities. Pb and Zn were controlled by traffic activities, and the accumulations of Ni and Hg were associated with mining activities. This study would be valuable for preventing heavy metals inputs and safety in rice production of the Songhua river basin.

Correlations between endoscopic and clinical disease activity indices in intestinal Behcet's disease

AIM:To develop a novel endoscopic severity model of intestinal Behcet's disease(BD) and to evaluate its feasibility by comparing it with the actual disease activity index for intestinal Behcet's disease(DAIBD).METHODS:We reviewed the medical records of 167 intestinal BD patients between March 1986 and April 2011.We also investigated the endoscopic parameters including ulcer locations,distribution,number,depth,shape,size and margin to identify independent factors associated with DAIBD.An endoscopic severity model was developed using significant colonoscopic variables identified by multivariate regression analysis and its correlation with the DAIBD was evaluated.To determine factors related to the discrepancy between endoscopic severity and clinical activity,clinical characteristics and laboratory markers of the patients were analyzed.RESULTS:A multivariate regression analysis revealed that the number of intestinal ulcers(≥ 2,P = 0.031) and volcanoshaped ulcers(P = 0.001) were predictive factors for the DAIBD.An endoscopic severity model(Y) was developed based on selected endoscopic variables as follows:Y = 47.44 + 9.04 × non-Ileocecal area + 11.85 ×≥ 2 of intestinal ulcers + 5.03 × shallow ulcers + 12.76 × deep ulcers + 4.47 × geographicshaped ulcers + 26.93 × volcano-shaped ulcers + 8.65 ×≥ 20 mm of intestinal ulcers.However,endoscopic parameters used in the multivariate analysis explained only 18.9% of the DAIBD variance.Patients with severe DAIBD scores but with moderately predicted disease activity by the endoscopic severity model had more symptoms of irritable bowel syndrome(21.4% vs 4.9%,P = 0.026) and a lower rate of corticosteroid use(50.0% vs 75.6%,P = 0.016) than those with severe DAIBD scores and accurately predicted disease by the model.CONCLUSION:Our study showed that the number of intestinal ulcers and volcano-shaped ulcers were predictive factors for severe DAIBD scores.However,the correlation between endoscopic severity and DAIBD(r = 0.434) was weak.

Improved 5-Aminolevulinic Acid Production with Recombinant Escherichia coli by a Short-term Dissolved Oxygen Shock in Fed-batch Fermentation

5-Aminolevulinic acid （ALA） is a common precursor for tetrapyrrole compounds in all kinds of organ isms and has wide applications in agriculture and medicines. In this study, a new strategy, i.e. short-term dissolved oxygen （DO） shock during aerobic fermentation, was introduced to produce 5-aminolevulinic acid with a recombi-nant E. coli. Effects of duration time of DO shock operation on plasmid concentration, intracellular ALA synthase （ALAS） activity and ALA production were investigated in Erlenmeyer shake flasks. The results indicated that both ALAS activity and ALA yield were enhanced in an anaerobic operation of 45 rain in the early exponential phase during fermentation, while they decreased when the anaerobic operation time was further increased to 60 rain. The DO shock protocol was confirmed with the fed-batch fermentation in a 15 L fermenter and the ALA production achieved 9.4 g.L-1 （72 mmol.L-1）, which is the highest yield in the fermentation broth reported up to now.

Large Deviations for a Generalized Compound Renewal Risk Model

This paper extends the ordinary renewal risk model to the case where the premium income process,based on a renewal counting process,is no longer a linear function;and the total claim amount process is described by a compound renewal process.For this realistic risk model,the large deviations for the claim surplus process is investigated.

Evolutionary Pattern and Effect of Administrative Division Adjustment During Urbanization of China:Empirical Analysis on Multiple Scales

The adjustment of administrative divisions is one of the important factors guiding China's urbanization, which has profound economic and social effects for regional development. In this paper, we comprehensively describe the process of the adjustment of administrative divisions at provincial and municipal levels in China and summarize the effects on the basic structure and patterns of the spatial development. We quantitatively assess the effects on fields such as urbanization and social economy through the use of multidimensional scaling. The results show that: 1) Upgrading county to municipality(or city-governed district) is the main way of adjusting the administrative divisions. It is also an important factor in the spatial differentiation of interprovincial urbanization. China's population urbanization can be divided into four patterns including interprovincial migration, provincial migration, natural growth, and growth caused by the adjustment of administrative divisions, which is also the main reason for the increased Chinese urbanization rate at the provincial level. 2) Taking the city of Beijing as an example, we generalize five adjustment patterns made to administrative divisions: the set-up of sub-districts, the set-up of regional offices, the upgrading of townships to sub-districts, the upgrading of townships to towns, and the set-up of towns and the addition of new regional offices. We summarize the municipal urban spatial structure, including the sub-district office area in the central urban area, the regional office area in the new urban area, the mixed area of villages, towns, and sub-district offices in the suburb area, and the township area in the outer suburb area. 3) The adjustment of administrative divisions triggers a significant circulative accumulation effect, resulting in the spatial locking of population and industrial agglomeration. It affects the evolution of the urban spatial form and plays an important role in shaping the urban spatial structure to move to the characteristic of multicenter. In general, the adjustment of administrative divisions was an important factor affecting the inflated statistical level of urbanization and also an important driving force for the evolution of Chinese urban spatial organization structure.

Structure of Mitochondrial DNA Control Region of Pholis fangi and Its Phylogenetic Implication

In this study, the entire mitochondrial DNA(mtDNA) control region(CR) of Pholis fangi was amplified via polymerase chain reaction followed by direct sequencing. The length of the mtDNA CR consensus sequence of P. fangi was 853 bp in length. In accordance with the recognition sites as were previously reported in fish species, the mtDNA CR sequence of P. fangi can be divided into 3 domains, i.e., the extended terminal associated sequence(ETAS), the central conserved sequence block(CSB), and the CSB domain. In addition, the following structures were identified in the mtDNA CR sequence of P. fangi: 2 ETASs in the ETAS domain(TAS and cTAS), 6 CSBs in the central CSB domain(CSB-F to CSB-A), and 3 CSBs in the CSB domain(CSB-1 to CSB-3). These demonstrated that the structure of the mtDNA CR of P. fangi was substantially different from those of most other fish species. The mtDNA CR sequence of P. fangi contained one conserved region from 656 bp to 815 bp. Similar to most other fish species, P. fangi has no tandem repeat sequences in its mtDNA CR sequence. Phylogenetic analysis based on the complete mtDNA CR sequences showed that there were no genetic differences within P. fangi populations of the same geographical origin and between P. fangi populations of different geographical origins.

Heavy Metal Analysis in Groundwater in the Vicinity of Distillery Spent Wash Evaporation Ponds

The study was conducted to assess the effect of evaporation ponds of an ethanol distillery spent wash on groundwater, with a reference to heavy metal contamination. The distillery discharging 11,880 m3 spent wash per day is extremely loaded with minerals and chemical oxygen demanding organic substances. The groundwater around the evaporation ponds is used for drinking and irrigation purposes. Thirty-five representative samples （three spent wash, two drainage water and 30 groundwater） were examined for 13 different parameters： pH, TDS （total dissolved solids）, COD （chemical oxygen demand）, the heavy metal Cd, Co, Cr, Cu, Fe, Mn, Ni, Zn, Pb and As concentrations. The physico-chemical parameters were found in following range pH 7.2-7.7 ＆ 6.8-7.7, TDS 24,448-28,608 mg/L ＆ 302-4,406 mg/L, COD 20,080-24,320 mg/L ＆ 0.0-53 mg/L, Cd 190-140 μg/L ＆ 1.5-8.7 μg/L, Co 1,240-1,987 μg/L ＆ 20.5-87.2 μg/L, Cr 1,020-1,330 μg/L ＆ 14.4-38.1 μg/L, Cu 5,200-6,300 μg/L ＆ 15.0-109.3 μg/L, Fe 2,910-3,242 μg/L ＆ 0-860 μg/L, Mn 49,900-59,500 μg/L ＆ 16.3-138.7 μg/L, Ni 1,430-1,760 μg/L ＆ 8.0-107.7 μg/L, Zn 3,359-5,250 μg/L ＆ 0.0-850 μg/L, Pb 8.9-9.8 μg/L ＆ BD （below detection）-8.7 μg/L, As 5.0 μg/L ＆ BD-10.0 μg/L for spent wash and groundwater samples, respectively. The drainage water samples had parameters within limits for industrial effluents. The spent wash samples contained metal ions higher than the permissible limits for industrial effluents and the samples of groundwater collected around the evaporation ponds contained higher concentrations of metal ions as compared to samples collected away from the evaporation ponds. Coefficient of correμtion among 11 parameters was calcuμted and contamination index was also determined, 33.3% of groundwater samples mostly collected around evaporation ponds had a contamination index above 3 and are considered extremely polluted.

Application of injury severity score to multiple injuries headed by spinal cord injury

Objective： To evaluate the application of injury severity score （ISS） to multiple injuries headed by spinal cord injury. Methods： The data of 55 cases （40 males and 15 females, aged 17-69 years, mean = 41 years） of multiple injuries headed by spinal cord injury treated in our hospital from January 2000 to December 2004 were reviewed and analyzed with ISS （Version of AIS-2005 ） to explore their relationship. Results ： The ISS values increased with the number of injured regions, so did the complications. The recovery rate was negatively related to ISS values. During the period of immunity observation, the patients with ISS 〉 25 could undergo planned operations safely. Conclusions： Treatment for multiple injuries headed by spinal cord injury closely depends on the general and local conditions of the patients. ISS may provide useful data for the choice of treatment methods.

Isolation,characterization,and phylogenic analysis of three new severe fever with thrombocytopenia syndrome bunyavirus strains derived from Hubei Province,China

Hubei Province is a major epidemic area of severe fever with thrombocytopenia syndrome bunyavirus(SFTSV) in China. However, to date, a few SFTSV strains have been isolated from Hubei Province, preventing effective studies of epidemic outbreaks. Here, we report three confirmed patients(2015–2016) with typical symptoms of severe fever with thrombocytopenia syndrome disease(SFTS) who were farmers resident in different regions in Hubei Province. Three new SFTSV strains were isolated from the serum samples of each patient. Characterization of viral growth properties showed that there were no significant differences in virus production. All strains were completely sequenced, and phylogenetic analysis showed that unlike the other strains from Hubei province, which belonged to the SFTSV C3 genotype, one of the three strains belonged to the SFTSV C2 genotype. These results suggested that multiple SFTSV genotypes have been circulating in Hubei Province, providing insights into SFTSV evolution and improving our understanding of SFTSV prevalence in Hubei Province.