A hybrid,finite element—finite difference approach to simplified large deflection analysis of structures

A new and considerably simplified solution technique for geometrically nonlinear problems is introduced. In contrast to the existing numerical methods, the present approach obtains an approximate large deflection pattern from the linear displacement vector by successively employing updated correction factors. Conservation of energy principle yields a general expression for these subsequent corrections. While the linear portion of the strain energy can be computed using finite element approach, evaluations of its nonlinear counterparts often require mathematical discretization techniques. The simple, self-correcting iterative procedure is unconditionally stable and its fast oscillatory convergence offers further computational efficiency. To illustrate the application of the proposed method and to assess its accuracy, moderately large deflections of beam, plate and flexible cable structures have been computed and compared with known analytical solutions. If required, the obtained results—which are acceptable for most design purposes—can be further improved.     

Polyionic fusion peptides function as specific dimerization motifs

The de novo design of a molecular adapter for directed associationand covalent linkage of two polypeptides is presented. Usingpeptides containing charged amino acid residues and an additionalcysteine residue (AlaCysLys₈ and AlaCysGlu₈) we demonstratethat the electrostatic interaction promotes the associationof two synthetic peptides and, subsequently, disulfide bondformation. The reaction depends on both the redox potentialand on the ionic strength of the buffer. Varying the redox potential,the interaction of the peptides was quantified by a G^0' of 6.6± 0.2 kcal/mol. Heterodimerization of the peptides ishighly specific, a competition of association by other cysteinecontaining compounds could not be observed. Two proteins comprisingcysteine-containing polyionic fusion peptides, a modified Fabfragment and an -glucosidase fusion, could be specifically conjugatedby directed association and subsequent disulfide bond formation.Both proteins retain their functional characteristics withinthe bifunctional conjugate: enzymatic activity of the glucosidaseand antigen-binding capacity of the Fab fragment are equivalentto the non-conjugated components.     

A new removable resist for high aspect ratio applications

A variety of different photo resists are used for fabrication of MEMS. Presently good results were reported for SU-8, a chemically amplified negative tone photoresist. But SU-8 has a disadvantage for some applications in LIGA technique, especially in the X-ray mask fabrication. After processing the finished resist pattern are hardly soluble from the substrate. This paper will briefly describe the current status of the development of the new negative tone photoresist CAR 44 whose big advantage is the easy removableness of the cross linked pattern. This work widely uses the contents of the presentation “A New Removable Resist for High Aspect Ratio Applications” to the High Aspect Ratio Micro Structure Technology workshop HARMST 2005 held in Gyeongyu (Republic of Korea), June 10–13, 2005.     

Disambiguating Visual Motion by Form-Motion Interaction—a Computational Model

The neural mechanisms underlying motion segregation and integration still remain unclear to a large extent. Local motion estimates often are ambiguous in the lack of form features, such as corners or junctions. Furthermore, even in the presence of such features, local motion estimates may be wrong if they were generated near occlusions or from transparent objects. Here, a neural model of visual motion processing is presented that involves early stages of the cortical dorsal and ventral pathways. We investigate the computational mechanisms of V1-MT feedforward and feedback processing in the perception of coherent shape motion. In particular, we demonstrate how modulatory MT-V1 feedback helps to stabilize localized feature signals at, e.g. corners, and to disambiguate initial flow estimates that signal ambiguous movement due to the aperture problem for single shapes. In cluttered environments with multiple moving objects partial occlusions may occur which, in turn, generate erroneous motion signals at points of overlapping form. Intrinsic-extrinsic region boundaries are indicated by local T-junctions of possibly any orientation and spatial configuration. Such junctions generate strong localized feature tracking signals that inject erroneous motion directions into the integration process. We describe a simple local mechanism of excitatory form-motion interaction that modifies spurious motion cues at T-junctions. In concert with local competitive-cooperative mechanisms of the motion pathway the motion signals are subsequently segregated into coherent representations of moving shapes. Computer simulations demonstrate the competency of the proposed neural model.     

Filaments for Incandescent Lamps with Energy Conserving Envelopes

The design considerations for filaments in energy conserving incandescent lamps are described. Such lamps require compact high emissivity filaments to absorb infrared radiation reflected from heat mirrored focusing envelopes. The relationships between the electrical parameters in the radiation returning environment and in the clear surroundings are developed. Efficiency experiments with filaments of various geometries under conditions of radiation return were performed. A highly compact coiled coil filament seems most promising for development. A calculation is presented of the filament emissivity as a function of spacing of the windings in a coil. Measurements of the emissivity as a function of the pitch of a coiled coil filament agree with the calculation.     

Image velocity, not tau, explains arrival-time judgments from global optical flow.

The time-to-passage (TTP; i.e., the time) until an object passes an observer is optically specified by global tau, a variable that operates on the expansion rate of the angle subtended by an object relative to the observer's heading. M. K. Kaiser and L. Mowafy (1993) provided evidence for observers' sensitivity to global tau in a 3-D cloud of point lights. This interpretation is challenged, and it is suggested that TTP judgments are based on a related but much simpler variable, the image velocity of the object. The present study reexamined several factors that are relevant for the extraction of global tau. When global tau and image velocity were brought into conflict by varying the lateral offsets of the targets, observers showed a strong tendency to rely on the latter variable. Other factors that are supposed to affect TTP judgments only if observers relied on global tau, such as flow-field density and gaze-movement angle, did not affect performance. (PsycINFO Database Record (c) 2011 APA, all rights reserved)