Toughening mechanisms in multiphase nanocomposites

Our research is concerned with nanoreinforced structural adhesive bonds (SAB) for aerospace applications that contain dissimilar substrates and a theromoset epoxy adhesive with dispersed nanofillers. The interactions between these different phases results in unique fracture properties and mechanisms that dictate the toughness of the nanocomposite. In view of the varied length-scale, one cannot implement mere traditional approaches to evaluate the possible toughening mechanisms needed to ensure the integrity of the multiphase nanocomposite. Our current research is devoted to establishing the appropriate toughening mechanisms in multiphase nanocomposites by adopting traditional mechanisms such as crack-bridging, crack deflection, crack pinning and void nucleation, as well as investigating new nano-mechanisms such as fracture ridge creation. In this paper, the toughening mechanisms of carbon nanotube (CNT) reinforced polymer SABs are identified and their effects quantified in order to effectively estimate the fracture toughness of nanocomposite. Specific attention is devoted to examining the effect of dispersion of the nanofillers upon the strengthening mechanisms and interfacial debonding in nanocomposites, and the propensity of agglomerations-assisted crack initiation sites using atomistic based continuum modeling techniques.     

新城市中心，斯图加特，德国

很久以来．斯图加特-法伊英根历史性的市中心就不是由教堂、市政厅和学校组成的．而是被庞大的酿酒厂建筑群所占据——它是这个城市最大的雇主单位，一个“巨形怪物”。在其他地方保留作为公共空间的地方．在这里却都被筑起围墙的酿酒厂占据了。名为“斯瓦比亚通廊”的新城市中心项目．第一次为法伊英根提供了一处拥有公共广场和公共建筑的真正的城市中心。     

Propagation of pulse trains through a random medium

Applying the parabolic approximation, the equations for two-frequency symmetric and antisymmetric mutual intensity functions for waves propagating through a random medium are derived, including the multiple scattering effects. These functions are applied to derive the general formulas for the covariance functions of narrowband pulses. They are used to compute the signal intensities for pulse trains passing through an ionospheric irregularity slab.     

Broadband public network and switch architecture

The authors present a view of public network and switch architecture evolution to broadband capabilities, driven by the applications evolutions and built on a synchronous fiber transmission infrastructure such as SONET (synchronous optical network). The scenario is based on the partitioning of broadband network functions between synchronous fiber transmission systems and cell-based transport. The first stage of evolution incorporates frame-based switching to support increasing data traffic for LAN (local area network) interconnections. Cell-based technology appears first in the form of point-to-point high-speed data trunks and then as switched high-speed access. Centralized cell switching will provide interconnect between cell-based trunks and shared access lines. Remote cell multipliers will provide traffic concentration when the number of customers further increases. Since cell transport will first be introduced in the network as an extension of frame transport to higher speed, interworking between cells and frames will be necessary     

On the heat in the nozzle of the industrial pneumatic pulsator

An industrially applicable nozzle is the subject of this study. The nozzle is an auxiliary equipment of a pneumatic pulsator system for unclogging outlets of silos which store loose materials. The aim is to determine the amount of heat which is generated during one work cycle of the system. Investigation in this field has not been carried out so far, and the present-day designing process is significantly based on heuristic knowledge. The heat is calculated by using results of a numerical simulation. The Finite Volume Method has been used with a thermodynamically ideal gas model. The airflow is assumed to be transient, compressible and supersonic, and it is driven by a time-varying pressure difference. There is an estimation of discretization error of the numerical results carried out in order to confirm the reliability of the solution. The error estimation shows that the results lie in the vicinity of the exact solution of the governing equations. Instantaneous results of the simulation indicate a locally flow which intensifies flow parameters in a similar way as the converging-diverging nozzles do. The value of the total heat generated during gas conversion within the nozzle is negative; thus, the nozzle could be cooled during its functioning.     

Traffic management for B-ISDN services

A set of asynchronous transfer mode (ATM) bearer service categories, differentiated in terms of quality of service (QOS), that will support the large spectrum of applications expected in broadband integrated services digital networks (B-ISDN) is defined. The evolution of applications and the traffic requirements in B-ISDN/ATM networks are described, and the evolution of network services to address these requirements is discussed. The definition of ATM bearer service categories necessary for the economical support of initial applications and evolution to future B-ISDN services is proposed. The elements of the ATM traffic management strategy to support these service categories are presented     

Evolution and service requirements of CBR applications on ATM networks

Broadband integrated networks based on asynchronous transfer mode (ATM) technology are being proposed to provide a single integrated access to a variety of services and applications. Constant bit rate services will form an important part of this unified networking solution. In this paper, we identify and describe the relevant aspects related to the implementation of CBR services on ATM. First, we identify two broad categories of potential CBR services for broadband ATM networks. The ATM infrastructure for the identified services is then developed along with the required functionalities of different network elements. Finally, end-to-end performance objectives for the ATM network are determined and verified empirically based on results of laboratory experiments. These performance objectives help us determine the minimum QOS required by the highest class of service category offered by an ATM network.