四川移动数据网络总体建设思路探讨

通过对省CMNET骨干网、IP城域数据网、IP宽带数据接入网3个主要网络层次的工程建设定位、技术特点、建设原则进行的分析,总结出在目前市场竞争条件下进行移动数据网络建设的相关思路。     

Sorption Equilibrium in Relation to the Spatial Distribution of Molecules — Application to Desorption of Potato

An analysis of desorption isotherms for potato shows the following probable qualities in the water-potato system. In the natural state the water is bound rather strongly due to loss of rotational degrees of freedom in the sorbed molecules, which is caused by small molecular voids in the cellulose structure. This structure therefore is formed as a uniformly cross bound state of the OH-groups. This state prevails up to a certain temperature, above which a reaction sets in, where OH bonds are successively broken, giving possibility for a partial rotation of sorbed molecules. In the range of lower moisture content the cellulose structure is changed into a crystalline state as in wood, although the degree of crystallinity is lower, which is the probable reason why the statistical fluctuations in the isotherms are greater for potato than for wood.     

Chemical composition of arctic snow: concentration levels and regional distribution of major elements

At the end of the northern winter 1996/1997, 21 snow samples were collected from 17 arctic localities in Norway, Sweden, Finland, Svalbard, Russia, Alaska, Canada, Greenland and Iceland. Major element concentrations of the filtered (0.45 mum) melted snow indicate that most samples are consistent with a diluted seawater composition. Deviations from this behaviour indicate additional SO(4)(2-) and Cl(-) relative to seawater, suggesting a minor contribution from (probably local) coal combustion emissions (Alaska, Finland, Sweden, Svalbard). The samples with the highest Na and Cl(-) content (Canada, Russia) also have higher Na/SO(4)(2-) and Cl(-)/SO(4)(2-) ratios than seawater, suggesting a slight contamination from (probably local) deicing activities. Local soil or rock dust inputs in the snow are indicated by 'excess' Ca contents (Alaska, Svalbard, Greenland, Sweden). No overall relationship was found between pH (range: 4.6-6.1) and total or non-seasalt SO(4)(2-) (NSS), suggesting that acidification due to long-range transport of SO(2) pollution is not operating on an arctic-wide scale. In a few samples (Alaska, Finland, Sweden, Svalbard), a significant proportion (>50%) of SO(4)(2-) is non-marine in origin. Sources for this non-marine SO(4)(2-) need not all be found in long-range atmospheric transport and more likely sources are local industry (Finland, Sweden), road traffic (Alaska) or minor snow-scooting traffic (one Svalbard locality). A few samples from northern Europe show a relatively weak trend of decreasing pH with increasing NO(3)(-).     

Latitudinal distribution of persistent organic pollutants in pelagic and demersal marine fish on the Norwegian Coast

The latitudinal distribution of persistent organic pollutants (POPs: legacy organochlorines [OCs], polybrominated diphenyl ethers [PBDEs,] and hexabromocyclododecane [HBCD]) was examined in livers of two species of marine fish, the pelagic saithe (Pollachius virens,n = 40) and the demersal cod (Gadus morhua,n = 40), along a south-north gradient (59°-70°N) on the Norwegian Coast. Cod had in general two to three times higher concentrations of POPs than saithe, probably because of higher exposure in the benthic food chain. The concentrations of heavy halogenated compounds were higher in the southernmost region than further north. Moreover, the POP pattern showed a gradual shift in the compositions from south to north, especially for OCs in cod: i.e. the relative importance of low-chlorinated polychlorinated biphenyl (PCB) congeners and some OC-pesticides (e.g., hexachlorobenzen [HCB]) in the contaminant burdens increased with latitude. The latitudinal fractionation signal was weaker in saithe, possibly due to its pelagic and nomadic behavior. Hence, this study shows not only a strong latitudinal fractionation in the compositional patterns of POPs in marine fish but also the effects of habitat use and fish behavior.     

技术哲学视阈中的风险和安全

对风险和安全哲学进行了概述,对与之相关的风险、不确定性、安全性和预防等核心概念进行了界定,特别强调了风险和不确定性的区分,并且论述了这种区分的重要性.以对科学中不确定性信息的处理的讨论为基础,论述了在科学的不确定性情形下进行决策的问题,澄清了预防原则的作用.探讨了如何实施安全工程的主要方法,强调了诸如内在安全性、安全因素和多重安全阻抗等安全原则的作用.在此基础上,指出风险性和安全性问题是技术哲学研究中的重要领域.     

Fatigue model for elastic bars in turbulent wind

Accumulated fatigue damage of an elastic structural bar vibrating in natural turbulent wind may be a primary cause of structural failure. Clumps of strong lateral oscillations may occur randomly with time. These oscillations are due to resonance between the vortex shedding frequency and the natural frequency of the bar. The so-called “lock in” phenomenon apparently extends resonance from a point of coincidence to an interval. An idealized stochastic model is set up on the basis of the empirically observed existence of a critical interval of undisturbed wind velocities upwind of the bar. The upwind velocities are modeled as realizations of a specific stochastic process. A clump of strong lateral, damped harmonic oscillations occurs during any uninterrupted “visit” of the velocity to the critical interval. For velocities outside the critical interval only insignificant lateral oscillations occur. The fatigue damage is assumed to be linearly accumulated according to the Palmgren—Miner rule within each clump and from clump to clump. The goal is to evaluate the structural reliability for any specified period of time. It is expressed in terms of a reliability index.