Geometric versus geographic models for the estimation of an FTTH deployment

Optical access networks provide a future proof platform for a wide range of services, and today, several operators are deploying fibre to the home (FTTH) networks. Installing an FTTH infrastructure, however, involves very high investment cost. Therefore, a good estimation of the investment cost is important for building a successful business strategy and, consequently, to speed up the FTTH penetration. In this paper, for calculating the amount of cable and fibre in the outside plant together with the associated civil works, and the number of required network elements, two different approaches are investigated: (1) geometric modelling of the fibre plant based on approximate mathematical models and (2) geographic modelling of the fibre plant based on map-based geospatial data. The results obtained from these two approaches can then be used as input for preliminary investment cost calculations and/or techno-economic evaluations. Compared to more complex and accurate geographic modelling, we verify that especially with uneven population density and irregular street system, simple geometric models do not provide accurate results. However, if no geospatial data is available or a fast calculation is desired for a first estimation, geometric models definitely have their relevance. Based on the case studies presented in this paper, we propose some important guidelines to improve the accuracy of the geometric models by eliminating their main distortion factors.     

Data fusion for ballistic targets tracking using least squares

The paper deals with the problem of state estimation of continuous-time nonlinear system using discrete-time measurements from multiple sensors. In particular, the problem of multi-radar tracking of artillery ballistic objects is considered. A batch estimator based on the iterative least squares approach is developed using simplified and accurate models of ballistic flight. The estimator is applied to process the sequences of measurements from radars tracking the same ballistic target. Estimates of the target state over time are computed and their accuracy is compared to the estimates yielded by the extended Kalman filter. Partial estimates from multiple radars are combined using track fusion approach and propagated using the 3 degree of freedom model of ballistic flight. Accuracy of target's firing point estimation is also analysed with respect to the data rates and locations of the radars with respect to the target. Practical aspects of the proposed method are also discussed.     

用于电子政府的数字签名-一种长期的安全结构

The framework of digital signature based on qualified certificates and X.509 architecture is known to have many security risks. Moreover, the fraud prevention mechanism is fragile and does not provide strong guarantees that can be necessary for flow of legal documents. Mediated signatures have been proposed as a mechanism to effectively disable signature cards. In this paper we propose further mechanisms that can be applied on top of mediated RSA, compatible with the standard format, but providing security guarantees even in the case when RSA becomes broken or the keys are compromised. The solution is immune tokleptographic attacks as only deterministic algorithms are used on user's side.     

Aromaticity as a Quantitative Concept. 2. Sixteen familiar five- and six-membered monocyclic heterocycles

Restudy of an almost complete data set of 12 characteristics for 16 common heterocycles confirms the previous conclusion [1] of the independence of „classical”︁ and of „magnetic”︁ aromaticity. The scores for the individual heterocycles correlate well with their chemical structure.     

Particulate Matter size distribution in the exhaust gas of a modern diesel Engine fuelled with a biodiesel blend

The characteristics of particulate mater size distribution in the exhaust gas of an automotive diesel engine have been studied for a biodiesel blend of 30% rapeseed methyl ester (RME) and 70% ultra low sulphur diesel (ULSD) by volume (B30). The engine, a twin-turbo charged V6 equipped with a common rail fuel injection system, was operated on 16 steady-state points extracted from a corresponding New European Driving Cycle test with no engine system modification and a fast differential mobility spectrometer was used to determine the particulate number concentration and distribution. It is shown that the number-size distribution is dependent on engine operating conditions including the rate of exhaust gas recirculation (EGR). Compared with ULSD, B30 leads to a 41% smaller average size of the particles with EGR but gives rise to a higher number concentration under certain engine operating conditions, with the differences varying between nucleation and accumulation mode. The calculated particle total mass for B30 combustion aerosol is lower than the value with ULSD for all the engine operating conditions tested. The average B30 aerosol was 28% smaller in size on mass basis, compared to ULSD aerosol. For both fuels, the relationship between the particle total number and total mass has been found to be directly correlated and both the number and the mass of particles increase when the mean diameters of particles increase.     

Design and investigation of a partial admission radial 2.5-kW organic Rankine cycle micro-turbine

In recent years, organic Rankine cycle (ORC) micro-turbine distributed energy systems have become increasingly popular. Design methods for this type of fluid-flow machinery are still being developed. In this paper, a 2.5-kW radial-flow four-stage ORC micro-turbine with HFE7100 is experimentally and numerically analysed. CFX ANSYS was used for the numerical analysis as well as a computational fluid dynamics (CFD) in-house code based on finite volume discretisation with Godunov-type upwind differencing, a high-resolution essentially non-oscillatory (ENO) scheme and a turbulence model with two-equation shear stress transport (SST). The experimental stand and measurements are described. The numerical results are compared with experimental ones and prove to be satisfactory. The developed micro-turbine does not require the use of any traditional lubricant (oil-free technology) because the bearings are lubricated with the vapour of the low-boiling HFE7100. The developed micro-turbine is an innovative solution providing maintenance-free operation and high durability with low friction losses. The experimental studies have also confirmed a considerable reduction in noise and vibration levels.     

均质压燃(HCCI)单区和多区燃烧模型的比较

利用耦合化学动力学软件包CHEMKIN建立了汽油HCCI发动机的单区和多区燃烧模型。与试验数据的对比表明：虽然单区模型在参数化研究中能较准确地预测混合气的自燃定时,但其准确性在很大程度上取决于缸内的均匀性;包含缝隙区、淬熄区、质量交换区和绝热核心区的九区燃烧模型通过设置特定的功能分区能更好地模拟HCCI的燃烧过程,它在对自燃定时的预测和对热量释放过程和排放物的形成机理的模拟等方面都有很好的性能。     

Total number of coding open reading frames in the yeast genome

At the end of 1996 we approximated the total number of protein coding ORFs in the Saccharomyces cerevisiae genome, based on their properties, as 4700–4800. The number is much smaller than the 5800 which is widely accepted. According to our calculations, there remain about 200–300 orphans—ORFs without known function or homology to already discovered genes, which is only about 5% of the total number of genes. Our results would be questionable if the analysed set of known genes was not a statistically representative sample of the whole set of protein coding genes in the S. cerevisiae genome. Therefore, we repeated our estimation using recently updated databases. In the course of the last 18 months, previously unknown functions of about 500 genes have been found. We have used these to check our method, former results and conclusions. Our previous estimation of the total number of coding ORFs was confirmed. Copyright © 1999 John Wiley & Sons, Ltd.     

The influence of gaseous chlorine on the chemical and catalytic properties of alumina

The influence of gaseous chlorine on the chemical and catalytic properties of alumina was investigated. Cl₂ reacts both with surface OH groups and with surface oxygen anions possessing electron-donating power, forming new surface sites. When such chlorine treatment is performed at a low temperature (293 K), both Lewis and Bronsted acid centres are formed. High temperature chlorination leads exclusively to Lewis acid sites. It is proposed that such Lewis sites are responsible for olefin isomerization reactions.