Improvement of the engineering properties of asphalt pavements using a ‘soft’ compaction technique (AMIR-Compaction)

In most countries of the world asphalt pavement of road networks represents the biggest single investment in the transportation system. In Canada, asphalt pavement built over the past decade is worth more than 70 billion dollars (in 1984 dollars). In order to maintain the current road network at the present level of service and prevent it from further deterioration, over 6 billion dollars is needed anually.

Traditionally, asphalt overlays are widely used to rehabilitate existing deteriorated pavements. Unfortunately the new overlays have been observed to fail in a relatively short time. Thus the investment in overlays is lost.

Recent research based on the concept of relative rigidity has indicated that the rapid deterioration of new asphalt overlays is directly related to current construction equipment. It has been shown analytically and experimentally that steel rollers used in compacting the asphalt layer will result in surface cracks during construction. Traffic and environmental influences will accelerate the failure of the new layer.

This paper presents the results of a testing programme evaluating the engineering properties of asphalt slabs compacted by a new method using a compactor termed AMIR. The results showed that the AMIR compactor will prevent the formation of constitution cracks resulting in an increase of indirect tensile strength of 10% and an increase of direct tensile strength of up to 60% when compared to steel roller compacted asphalt slabs.     

Effect of shot noise and secondary emission noise in scanning electron microscope images

The effect of shot noise and emission noise due to materials that have different emission properties was simulated. Local variations in emission properties affect the overall signal‐to‐noise ratio (SNR) value of the scanning electron microscope image. In the case in which emission noise is assumed to be absent, the image SNRs for silicon and gold on a black background are identical. This is because only shot noise in the primary beam affects the SNRs, irrespective of the assumed noiseless secondary electron emission or backscattered electron emission processes. The addition of secondary emission noise degrades the SNR. Materials with higher secondary electron yield and backscattering electron yield give rise to higher SNR. For images formed from two types of material, the contrast of the image is lower. The reduction in image signal reduces the overall image SNR. As expected, large differences in δ or η give rise to higher SNR images.     

Raft crystals of poly(isoprene)-block-poly(ferrocenyldimethylsilane) and their surface wetting behavior during melting as observed by AFM and NanoTA

We report on the morphology evolution during heating and melting of lamellar poly(isoprene)-block-poly(ferrocenyldimethylsilane) (PI₇₆-b-PFDMS₇₆) raft crystals deposited at the native oxide surface of silicon (SiO₂) or at a highly ordered pyrolytic graphite (HOPG) surface, studied by in situ temperature controlled atomic force microscopy. Crystals deposited on hydrophilic SiO₂ surfaces revealed an irreversible decrease in length at temperatures of up to tens of degrees above their expected melting temperature, while maintaining their platelet-like structure. Crystals deposited on hydrophobic HOPG surfaces initially decreased in length below their expected melting temperature, while at 120 °C and above a typical molten morphology was observed. In addition, the irreversible formation of a PI₇₆-b-PFDMS₇₆ wetting layer around the crystals was observed upon increasing the temperature. These observations in the morphological behavior upon heating emphasize the role of interfacial energy between a surface deposited block copolymer based macromolecular nanostructure and its supporting substrate.     

Comparative Analysis of Scanning Electron Microscopy Techniques for Semiconductors: Electron-Beam-Induced Potential Method,Single-Contact Electron-Beam-Induced Current Method,and Thermoacoustic Detection

The potentialities of three techniques for detecting signals from barrier structures in a scanning electron microscope are discussed. All the methods are virtually contactless; that is, it is only required that the chips are grounded. The relaxation behavior of the signals is considered. The invalidity of the thermoacoustic detection technique is shown. It is experimentally demonstrated that information extracted with the method of electron-beam-induced surface potential is identical to that obtained by thermoacoustic detection.     

A study of dual-mode bandpass filter integrated in BGA package for single-chip RF transceivers

This paper presents a study of a dual-mode bandpass filter integrated in a ball grid array (BGA) package for the single-chip solutions of radio frequency (RF) transceivers. The novel in-package filter, except for the economical advantage of mass production and automatic assembly, has potential benefit to the system-level board miniaturization and the system-level manufacturing facilitation. The simulated and measured performance of the in-package filter is presented. The effects of the different physical parts of the package on the filter performance are investigated. Experimental results show that the in-package filter of size 15/spl times/15/spl times/1.905 mm/sup 3/ achieved 3-dB percentage bandwidth of 14% and insertion loss of 2.07 dB at 5.25 GHz.     

Shape‐Shifting 3D Protein Microstructures with Programmable Directionality via Quantitative Nanoscale Stiffness Modulation

The ability to shape‐shift in response to a stimulus increases an organism's survivability in nature. Similarly, man‐made dynamic and responsive “smart” microtechnology is crucial for the advancement of human technology. Here, 10–30 μm shape‐changing 3D BSA protein hydrogel microstructures are fabricated with dynamic, quantitative, directional, and angle‐resolved bending via two‐photon photolithography. The controlled directional responsiveness is achieved by spatially controlling the cross‐linking density of BSA at a nanometer lengthscale. Atomic force microscopy measurements of Young's moduli of structures indicate that increasing the laser writing distance at the z‐axis from 100–500 nm decreases the modulus of the structure. Hence, through nanoscale modulation of the laser writing z‐layer distance at the nanoscale, control over the cross‐linking density is possible, allowing for the swelling extent of the microstructures to be quantified and controlled with high precision. This method of segmented moduli is applied within a single microstructure for the design of shape‐shifting microstructures that exhibit stimulus‐induced chirality, as well as for the fabrication of a free‐standing 3D microtrap which is able to open and close in response to a pH change.     

Temporal changes in the periphytic algal communities in a drowned tropical forest reservoir in Malaysia: Lake Kenyir

Periphytic algal assemblages, comprising bacillariophytes, cyanophytes and chlorophytes of standing dead trees in Lake Kenyir, a tropical drowned forest reservoir, were studied during 1995. A total of 317 algal taxa were identified in this study. The monthly floral mean species richness and cell count data demonstrated significant temporal differences between the months, in one-way anova (P < 0.05). Both redundancy analysis and cluster analysis on monthly blue-green abundance and diatom assemblages exhibited conspicuous groupings among the months, with underpinning seasonal differences. The responses were not similar, however, between the upstream and downstream ends of the lake. The grouping or clustering of months can be generalized as: (i) November, December and January as the monsoonal months; (ii) February, March, April and May as the transitional months; and (iii) June to October as the dry months. Based on stepwise multiple regression with forward selection, alkalinity and dissolved oxygen concentration were significant environmental predictors at the downstream dam sampling site, and reactive silica, electrical conductivity, Secchi depth transparency and sunshine hours were significant predicators at the upstream riverine sampling site, based on Monte Carlo tests. Being a ploymictic, mesotrophic lake, the limnology and temporal changes for Lake Kenyir appears to be complex and driven by monsoons, as evidenced from the temporal changes in its periphytic algae communities, particularly the diatom assemblages. The downstream sampling site (site 1) at the dam, in the main basin and deeper zone of the lake, the seasonal amplitude was likely complex because of thermocline formation and stratification processes. In contrast, the upstream sampling site in the Petang River (site 2) exhibited a clearer distinction between the dry and monsoon months, based on its cyanophyte and diatom floral assemblages. These study results are pertinent for lake management, especially for developing biomonitoring programmes or lake productivity studies, as well as for climate change studies, within the context of tropical lake ecology.     

Accurate analytical method for the extraction of solar cell model parameters

Analytical expressions are derived for the rapid extraction of solar cell single diode model parameters from experimental data. The resulting parameter values are shown to have less than 5% error for most solar cells     

Pyrroline-5-carboxylate reductase in human erythrocytes

Pyrroline-5-carboxylate reductase, which converts pyrroline-5-carboxylate to proline, has been identified in human erythrocytes. The level of pyrroline-5-carboxylate reductase activity in these cells is comparable to the activity levels of major erythrocyte enzymes. The physiologic function of the enzyme in erythrocytes cannot be related to its function in other tissues, i.e., producing proline for protein synthesis. We examined the kinetic properties of erythrocyte pyrroline-5-carboxylate reductase and compared them to the properties of the enzyme from proliferating cultured human fibroblasts. We found that the kinetic properties and regulation of the erythrocyte enzyme are distinctly different from those for human fibroblast pyrroline-5-carboxylate reductase. These characteristics are consistent with the interpretation that the function of the enzyme in human erythrocytes may be to generate oxidizing potential in the form of NADP+.     

Line width control in electron-beam lithography

A method for predicting line widths in electron beam lithography is described. Computer predictions of line dimension as a function of dose, and profile as a function of proximity to another line are compared with experimental results on 0.35?m thick PMMA at a beam energy of 15 keV.