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.     

Dynamic Testing of Prestressed Concrete Bridges and Numerical Verification

This paper describes different dynamic tests carried out on three bridges, B14, B15, and B13, over highway E19, which connects Brussels and Antwerpen in Belgium. Different excitation types are considered: a drop weight, a heavy truck on the bridge, and ambient vibrations mainly due to the traffic under the bridge. Finite-element models are constructed to support and verify the dynamic measurements. The modal parameters are extracted from the response time series using the data dependent system approach. A vector autoregressive model is developed and successfully applied to the measured responses in time domain. Good correlation between the finite-element simulations and the experiments is obtained.     

Visual tracking using convolutional features with sparse coding

Artificial Intelligence Review - Visual object tracking has become one of the most active research topics in computer vision, and it has been applied in several commercial...     

Observations of slip patterns on the surface of fatigued gold using the scanning tunnelling microscope

Observations of fatigue-induced slip patterns on the surface of polycrystalline gold (+99.9%) using the scanning tunnelling microscope (STM) are presented. The samples were cycled in four-point bending between zero and 0.0025 strain for 250 and 2500 cycles. STM observations of the sample fatigued for 250 cycles revealed broad slip bands 0.38–0.69 m wide containing narrow slip bands 0.015–0.123 m wide and fine slip lines 0.006 m wide. The depth of these features are 20–57 nm for broad slip bands, 3–7 nm for narrow slip bands, and approximately 2–4 nm for fine slip lines. The sample fatigued for 2500 cycles showed similar values for the width of the slip bands and slip lines except that their depth was increased by a factor of between 2 and 4 times for the narrow slip bands and the fine slip lines. Apparent persistent slip bands (PSBs) spaced 2.4 m, 300–500 nm deep were also observed. These results demonstrate that STM is a significant new tool for observing and distinguishing various types of fatigue-induced surface slip patterns on suitably prepared samples. The vertical resolution obtained with STM is vastly superior to current SEM and TEM methods.     

Autocatalytic dissolution of Pb in HNO3

The reaction between Pb and HNO₃ has been investigated using the thermometric technique. Weight-loss measurements on the reaction were also obtained. As the HNO₃ concentration is increased from 5×10^–2 to 4mol l^–1, the corrosion rate increases. This is shown thermometrically by a substantial increase in the maximum temperature attained, T _m, as well as a decrease in the time, t, required for reaching T _m. Dissolution of Pb in HNO₃ is proposed to take place according to an autocatalytic mechanism. Passivation sets were detected in solutions 11 mol l^–1 HNO₃. A parallel indication between the thermometric technique and weight-loss measurements was obtained. The rate-determining step of the autocatalytic process involves HNO₂ in dissolution of Pb in HNO₃. This is supported by the results of addition of hydrazine to the solution. This additive raises the maximum measured temperature, without affecting the corresponding time necessary to reach it. The effect of addition of NaNO₂, NaNO₃, NaCl, Na₂SO₄, NaH₂PO₄ and NaClO₄ on the reaction number, RN, of Pb in 4 mol l^–1 HNO₃ was examined. Only NaNO₂ accelerates the dissolution reaction while the other salts show as inhibition effect. It was found that these additives inhibit dissolution due to the displacement of some cathodic depolarizing components, as NO₂, from the active sites on the metal surface. The effect of addition of HCl, H₂SO₄, HClO₄ and H₃PO₄ on the reaction number, RN, of Pb in 4 mol l^–1 HNO₃ was also investigated. The observed acceleration and retardation of the dissolution of Pb was found to be dependent on both the concentration and nature of anions of the extra acids added.     

A 2-D five-noded finite element to model power singularity

A 2-D five-noded finite element which contains a singularity is developed. The new element is compatible with cubic standard isoparametric elements. The main advantage of using cubic isoparametric elements over quadratic elements is to reduce the number of elements required to model a structure for results of comparable accuracy. The element is tested on two different examples. In the first example, an edge crack problem is analyzed using two different meshes. The second example is a crack perpendicular to the interface problem which is solved for two different specific composites. The results obtained using the proposed element are compared with those obtained using other existing elements in the literature. Those comparisons demonstrate the superiority of the present technique in using less number of elements and nodes to produce accurate results.     

Effect of SiO2 Addition on Chromium Transitions in Borate Glasses

Silicon - Melt-quenching technique was used to prepare borosilicate glasses of composition xSiO2- (75-x) B2O3–24.7Li2O-0.3Cr2O3 (x = 0, 10, 20, 30, 40 and 50 mol%). With...     

Electrocopolymerization kinetics of a binary mixture of 3‐chloroaniline 2‐amino‐4‐phenylthiazole and characterization of the obtained block copolymer films

Electrocopolymerization of a binary mixture of 3‐chloroaniline and 2‐amino‐4‐phenylthiazole on platinum electrode in acid medium was carried out under different reaction conditions such as temperature, current density, hydrochloric acid, and monomer concentrations with duration time. The initial rate of the electrocopolymerization reaction on platinum electrode is small and the rate law is R_p = K₂ [D]^1.29[HCl]^0.97[M]^1.94. The apparent activation energy is found to be 38.87 kJ/mol. The obtained copolymer film is characterized by ¹H‐NMR, elemental analysis, GPC IR, UV‐visible, and cyclic voltammetry and compared with those of the two homopolymers. The mechanism of the electrocopolymerization reaction is also discussed and the monomer reactivity ratio (r₁and r₂) is calculated. The thermogravimetric analysis (TGA) is used to confirm the proposed structure and determination of the number of water molecules in the polymeric chain unit. X‐ray and scanning electron microscopic analysis are used to investigate the surface morphology. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2076–2087, 2005     

Dynamic watermarking scheme for quantum images based on Hadamard transform

In this paper, a novel watermarking scheme for quantum images based on Hadamard transform is proposed. In the new scheme, a unitary transform controlled by a classical binary key is implemented on quantum image. Then, we utilize a dynamic vector, instead of a fixed parameter as in other previous schemes, to control the embedding process. The dynamic embedding vector is decided by both the carrier quantum image and the watermark image, which is only known by the authorized owner. The proposed scheme is analyzed from visual quality, computational complexity, and payload capacity. Analysis and results show that the proposed scheme has better visual quality under a higher embedding capacity and lower complexity compared with other schemes proposed recently.