Eigenvalue sensitivity analysis of stiffened plates with respect to the location of stiffeners

This paper formulates the eigenvalue sensitivity of a stiffened plate with respect to stiffener location; the analysis is based on the generalized Rayleigh quotient of the combined platebeam system. The results show that the eigenvalue sensitivity is proportional to the force between the plate and the stiffener as well as to the slope of the eigenfunction at the interface between the plate and the stiffener.     

Dynamic adaptation of network connections in mobile environments

Most network applications assume continuous connectivity-an assumption that does not “migrate” to wireless environments. The authors present the design of a communication layer for mobile computing that dynamically adapts to changes in network connections. Our work was part of AMIGOS (Advanced Mobile Integration in General Operating Systems), a collaboration between researchers at the University of Copenhagen in Denmark and the University of Minho in Portugal. The AMIGOS project provides transparent support for semi connected operations on mobile computers running a standard operating system; the project home page is at http://www.econ.cbs.dk/people/birger/AMIGOS/. Briefly, our design lets a mobile user connect a mobile host to a LAN, then disconnect the host from it. The user then can reconnect, for example, via a Global System for Mobile Communications (GSM) cellular modem without losing TCP/IP connections. We want to allow existing TCP/IP based applications to be used in a mobile environment, without application modifications     

Mechanical characterization and design of flexible silicon microstructures

A variety of different silicon structures has been fabricated and characterized mechanically to optimize the design of silicon ribbon cables used in neural probes and multichip packaging structures. Boron-doped 3-/spl mu/m-thick silicon beams were tested in three modes: bending in plane, twisting (along beam axis), and pushing. Various cable configurations were investigated (straight beams, curved beams, meandered beams, etc.) as well the effects of length, width, cable termination, and the presence of reinforcing spans between multistranded cables. The results along with finite element modeling indicated that many simple modifications could be made to increase the strength and flexibility of silicon ribbon cables. One structure, a meandered beam 200-/spl mu/m wide and 2-mm long could be twisted up to 712/spl deg/. It also was seen that structures having multiple 20-/spl mu/m-wide beams were generally more robust than those with a single 500-/spl mu/m-wide beam. Finally, a method for easy determination of the bending fracture strain is analyzed and verified. It was seen that the silicon structures tested broke after a strain slightly above 2%.     

Extrudate expansion model in a twin-screw extrusion cooking process considering melt rheological property

A new extrudate bulk density model framework was developed, which is taking into account the melt rheological effects based on mixing principle and non-Newtonian power law theory for a twin-screw extrusion cooking process. The main ingredients in the extrusion process investigation were wheat, fish meal and soybean protein. The average absolute deviation (AAD) of the model prediction for extrudate bulk density is 5.3 % for the investigated process. The prediction results demonstrate that the proposed equation can be used to model the extrudate bulk density in the twin-screw extruder extrusion cooking process.     

Electric Properties of Semiconductor Nanopillars

We studied the electrical transport through epitaxial, 8 nm long and about 100 nm diameter, GaAs pillars. They are fabricated with molecular beam epitaxy using a self-assembling method called local droplet etching. The nanopillars are embedded in an AlGaAs tunneling barrier between two epitaxial GaAs layers. Because of the epitaxial growth, the pillars are connected to these GaAs layers without additional interfaces. They thus can be considered as electronic point contacts between three-dimensional electron reservoirs. Voltage-current characteristics of the structures feature a characteristic asymmetry that is not observed in reference samples. Furthermore, the behavior of the resistance in magnetic fields applied parallel and perpendicular to the current direction is compared for samples with and without pillars. Clear differences are found that are associated with current-carrying states in the pillars.     

明式家具的丹麦知音

<正>即使在北欧人力费用极高的情况下,卡尔·汉森·桑仍以近乎苛刻的标准进行手工制作,并将这份永恒的经典和淡然的精致传递给全世界的使用者。丹麦设计界流传着这样一则故事:1807年,英国轰炸丹麦首都哥本哈根。时任丹麦国王下令从斯德哥尔摩南部到汉堡北部,用一切办法遍植橡树以躲避战争的创伤,并规定:"每棵树都不可被砍掉,除非新种一棵。"结果,战争的炮火并未殃及丹麦,这些橡树幸运存活了下来,年复一年,长成茂密森林。闻着木香,我们来到哥本哈根繁华都市的心脏处——自1780年起就开始引领丹麦设计与工艺时尚的Bredgade大街,百年品牌卡尔·汉森·桑(Carl Hansen&Son)全球旗舰店就坐落于此。     

Democracy and non-profit housing. The tensions of residents’ involvement in the Danish non-profit sector

Resident democracy as a special form of participatory democratic set-up is fundamental in the understanding, and self-understanding, of the non-profit housing sector in Denmark. Through a case study, the paper explores how resident democracy is perceived and narrated between residents and employees at a housing association. The study indicates that the meta-story of democracy is disconnected from practice and the lived lives of residents. Three analytical tensions structure the analysis, which relate to the conditions for realizing the democratic ideal embedded in the structure of the sector. The tensions are related to representative versus participatory democracy; collectivity versus individuality; and service versus welfare. The tensions elucidate how resident democracy is squeezed between different logics, which result in an ambiguous setting for practising democracy. Based on the results, the article discusses conditions for prospective democracy in the Danish non-profit housing sector.     

Transversely compressed bonded joints

The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using non-linear fracture mechanics. The results indicated a good correlation between theory and tests. Furthermore, the model is suggested as theoretical base for determining load capacity of bonded anchorages with transverse pressure, in externally reinforced concrete structures.