Compact ultra-fast vertical nanopositioner for improving scanning probe microscope scan speed

The mechanical design of a high-bandwidth, short-range vertical positioning stage is described for integration with a commercial scanning probe microscope (SPM) for dual-stage actuation to significantly improve scanning performance. The vertical motion of the sample platform is driven by a stiff and compact piezo-stack actuator and guided by a novel circular flexure to minimize undesirable mechanical resonances that can limit the performance of the vertical feedback control loop. Finite element analysis is performed to study the key issues that affect performance. To relax the need for properly securing the stage to a working surface, such as a laboratory workbench, an inertial cancellation scheme is utilized. The measured dominant unloaded mechanical resonance of a prototype stage is above 150 kHz and the travel range is approximately 1.56 μm. The high-bandwidth stage is experimentally evaluated with a basic commercial SPM, and results show over 25-times improvement in the scanning performance.     

Document image decoding by heuristic search

This correspondence describes an approach to reducing the computational cost of document image decoding by viewing it as a heuristic search problem. The kernel of the approach is a modified dynamic programming (DP) algorithm, called the iterated complete path (ICP) algorithm, that is intended for use with separable source models. A set of heuristic functions are presented for decoding formatted text with ICP. Speedups of 3-25 over DP have been observed when decoding text columns and telephone yellow pages using ICP and the proposed heuristics     

Variational approach to fluid-structure interaction with sloshing

A general variational principle for fluid-structure interaction problems with sloshing is presented. Both seismic and body forces are accounted for in the development. It is shown that various fluid-structure interaction formulations can be obtained from the developed functional.     

Recent development in the fast corrosion fatigue analysis of offshore structures subject to random wave loading

In many areas of engineering, such as the offshore industry, welded steel joints are widely used as standard structural components. These joints are usually subject to long-term random wave loading and are therefore susceptible to fatigue damage. In many cases, the complex service loading is described by stress (or strain) power spectra, each representing a stationary sea state. These power spectra are obtained from hydrodynamic analysis or in situ monitoring. These will then be used in design calculations, feasibility studies or in-service assessment of fatigue damage on the structures.

Usually, the power spectra will have to be realized into real-time histories and then counted before fatigue analysis can be carried out. On many occasions where a large number of design options or joints need to be analysed, this process becomes very time consuming and expensive. The situation is further complicated by the calculations involving corrosion fatigue for joints in sea water.

The paper will start with a brief presentation of the fatigue analysis procedures for offshore welded joints and several existing models that were derived to bypass the laborious load history analysis mentioned above. More effort, however, will be concentrated on presenting the development of a new model. This model not only provides a more consistent and accurate prediction, but has also been adopted successfully for corrosion fatigue analysis.     

Reactions of [14C]-3,4-dichloroisocoumarin with subunits of pituitary and spleen multicatalytic proteinase complexes (proteasomes)

Exposure to [14C]-3,4-dichloroisocoumarin (DCI) of multicatalytic proteinase complexes (MPC) isolated from bovine pituitary and spleen leads to label incorporation into several beta-type subunits, to rapid inactivation of the chymotrypsin-like (ChT-L) activity, and to a slower inactivation of other activities of the MPC. The pituitary and spleen MPCs differ in that the first contains almost exclusively the X, Y, and Z subunits, whereas in the latter these subunits are largely replaced by LMP2, LMP7, and MECL1. Preincubation with two peptidyl aledhyde inhibitors of the ChT-L activity protected the X subunit in the pituitary MPC and unexpectedly the LMP2 subunit in the spleen MPC from label incorporation, despite the greater amino acid sequence homology of the LMP7 subunit to that of the X subunit. Losses in the yield of amino acids in both subunits, shown by amino acid sequencing, and lability of the DCI-protein bond indicated formation of an acyl derivative by reaction of DCI with the threonine OH group. Brief exposure to [14C]-DCI led to preferential incorporation of label into the LMP2 and X subunits, consistent with the high inactivation rate constants of the ChT-L activity. Z-LLF-CHO, an inhibitor of ChT-L activity, but not Z-GPFL-CHO, an inhibitor of the branched chain amino acid preferring component, prevented incorporation of radioactivity into the X subunits, whereas both inhibitors prevented label incorporation into LMP2, indicating differences in susceptibility to inhibition between the two components. These and other data are consistent with involvement of the X and LMP2 subunits in expression of the ChT-L activity in the pituitary and spleen MPC, respectively, and suggest the catalytic functions of two other beta-subunits.     

Effect of lactation on diurnal temperature patterns of dairy cattle in hot environments

Vaginal temperature patterns were obtained from 15 Holstein cows through radiotelemetry. Animals were divided into three groups with five animals per group: 1) cows in early lactation, less than 100 days postpartum, 2) cows in late lactation, greater than 240 days postpartum, and 3) dry cows. Animal temperatures, dry bulb, wet bulb, and black globe temperatures were monitored every 15 min for 17 days. Analysis of variance showed no significant difference for daily mean vaginal temperature between lactation groups. However, on hotter days, lactating cows had higher temperatures than dry cows. Daily mean vaginal temperatures of cows in early lactation were correlated with daily mean dry bulb temperature, black globe temperature, and relative humidity. Comparison of group temperature patterns isolated differences to specific times of day. In groups with early and late lactations, temperatures were lower in either group after milking. Vaginal temperatures were higher in lactating cows than in dry cows through most of the day. Results were 1) diurnal temperature patterns differ among groups; 2) lactating cows are sensitive to environmental changes; and 3) animal management can affect patterns of animal temperature.     

Partitioned rational Runge Kutta for parabolic systems

A new family of coupled time integration operators of different orders is developed. It permits different time integration operators to be used simultaneously in various regions of the model. This approach has the advantage of applying a very accurate time integrator, such as Runge Kutta method of order two to four, to the local nonlinear region of interest and a simple time integrator, such as the implicit–explicit or mixed time implicit–explicit method of order one, for the remaining region. The computer implementation aspects, stability analysis as well as the numerical evaluations of these new methods are presented. This is another attractive addition to the repertoire of time integration methods.