Evaluation of IP over WDM Network Architectures

The commonly used IP-backbone network architecture of today is IP/ATM/SDH/WDM. This architecture has many redundant functionalities and is not optimized to transport IP traffic. New approaches for simplified network architectures try to eliminate redundant functionalities and to decrease the protocol overhead and thereby transport IP as efficiently as possible over WDM-based optical networks. EURESCOM project P918 Integration of IP-over-optical networks: networking and management investigated scenarios for optimized IP transport in WDM-based backbone networks. In this paper, three architectures, namely Gigabit Ethernet, Packet over Sonet/SDH and Dynamic Packet Transport are investigated and evaluated as an alternative to the IP/ATM/SDH/WDM architecture.     

非整数阶系统连续时间域的模拟

提出了一种致力于非整数阶系统连续时间域的模拟方法.这种特殊系统的仿真建立在有限频率区间非整数阶积分算子的基础上,其非整数阶作用仅限于有限频率区域.然后,可以定义非整数阶模型的状态方程实现,它允许近似理想非整数阶系统的连续时间响应.最后,通过两个数字仿真例子来验证这种模拟方法.     

升温速率对氧化铝粉末烧结行为的影响

采用不同的升温速率,在膨胀计中对脱脂后的氧化铝粉末射成形坯件进行一系列的烧结试验.结果表明,烧结致密化过程主要发生在升温阶段,快速升温有利于致密化的进行和抑止晶粒长大,但由于烧结时间较短和烧结炉最高温度的限制,产品的最终致密化程度不高.在低温时快速升温,高温时缓慢加热,可以获得较好的致密化效果和微观结构.试验和分析结果将为建立非等温烧结模型和烧结工艺参数的优化方法提供依据.     

Thermal patterns in evaporating liquid

In this paper, some of the preparatory experiments of the ESA sponsored space program CIMEX-1 are presented. A liquid layer of variable thickness is subject to a flow of inert gas. The non-uniform evaporation induced by the gas flow creates a temperature gradient parallel to the interface triggering in that way thermocapillary convection. The combined action of evaporation, thermocapillarity and gravity has been not completely clarified both theoretically and experimentally. The experiment presented in this work concerns a liquid layer of ethanol of 2.2 mm thickness in presence of a mass flow of Nitrogen whose intensity varies in the range of hundreds of milliliter per minute. The experiments were performed at an initial liquid temperature of 21°C. The patterns observed are strongly dependent on the flow rate of inert gas. A change in the instability patterns has been observed for a gas flow of about 1.7 l/min.     

Stress Intensity Factor Gauging by Digital Image Correlation: Application in Cyclic Fatigue

Abstract:  A fatigue crack in steel (CCT geometry) is studied via digital image correlation. The measurement of the stress intensity factor (SIF) change during one cycle is performed using a decomposition of the displacement field onto a tailored set of elastic fields. The same analysis is performed using two different routes, namely, the first one consists in computing the displacement field using a general correlation technique providing the displacement field projected onto finite element shape functions, and then analysing this displacement field in terms of the selected mechanically relevant fields. The second strategy, called integrated approach, directly estimates the amplitude of these elastic fields from the correlation of successive images. Both procedures give consistent results, and offer very good performances in the evaluation of the crack tip position (uncertainty of about 20  μ m for a 14.5-mm crack), SIFs (uncertainty <1 MPa ) and opening properties.     

Dedicated SAR interferometric analysis to detect subtle deformation in evaporite areas around Zaragoza,NE Spain

A high density of local natural and human-induced ground deformation structures resulting from the presence of evaporites occur extensively around Zaragoza (NE Spain), posing risks to infrastructure, buildings and agriculture. We studied the potential of a series of interferograms constructed from 29 European Radar Satellite (ERS)-1/2 images to detect different types of ground deformation related to evaporite dissolution, landslides and mining subsidence. We examined the factors involved in the usefulness and quality of interferograms, especially in relation to coherence and atmospheric circumstances. Favourable conditions were found in desert or developed areas, while agricultural practises caused decorrelation in most sinkhole-prone areas. Results are consistent with previous geomorphological data and indicate that different natural and human-induced deformation phenomena can be detected in a time lag less than 5 years in evaporite areas. Advanced interferometric techniques based on time series of SAR images are needed for precise measurement and monitoring purposes.     

Three-dimensional analysis of a compression test on stone wool

A full three-dimensional (3D) study of a compression test on a sample made of stone wool is presented. The analysis combines different tools, namely X-ray microtomography of an in situ experiment, image acquisition and treatment, and volume correlation. This set of tools allows for the measurement of 3D displacement fields and enables Poisson’s ratio of this type of material to be evaluated. The strain fields are used to analyze localization phenomena. The uncertainty of the analysis is evaluated by actually moving the sample in its undeformed and deformed states, qualifying both image acquisition and correlation steps.     

A vectorial algorithm for tracing discrete straight lines inN-dimensional generalized grids

This paper presents an algorithm to trace discrete straight lines in regular grids of any dimension. Most known line tracing algorithms have been developed in Z² and Z³ orthogonal grids. The contribution of this paper is the definition of a method to trace lines in nonorthogonal grids in any dimension. This method is not restricted to being used with a specific grid connectivity as other widespread methods are. Good performance can be achieved because only additions are used during line tracing