In this study, a supervised machine learning network model is proposed to detect and classify various types of cracks developed in asphalt pavements, including lane markers. Crack images captured ...from a digital camera are classified into nine categories following the pavement distress identification manual proposed by the Federal Highways Administration (FHWA). These categories are three different types of cracks, such as fatigue, longitudinal, and transverse cracks with three severity levels of the low, medium, and high for each crack type. To establish a training dataset for crack detection, 1000 images with the original size of 3704 × 10,000 pixels are divided into 20,000 smaller images of 1852 × 1000 pixels image size. The training images are labeled based on the nine categories and trained using an updated version of faster R-CNN called RetinaNet. The trained network model is validated using pavement surface images obtained from 2400 m of two road sections. It is observed from the validation study that the detection and classification accuracy of the trained network model is 84.9% considering both the crack type and severity level. When considering the crack type only, the detection accuracy of the network model is 89.1%.
Abstract The self-assembling formation of Si quantum dots (Si-QDs) on as-grown SiO 2 layers was shown by controlling the early stages of low-pressure chemical vapor deposition of SiH 4 . The QD ...height and radius distributions assessed by atomic force microscopy and scanning electron microscopy images revealed that the Si-QDs become hemispherical due to them being rate-limited by aggregation, which reduces the surface energy at substrate temperatures above ∼580 °C. Moreover, at temperatures below ∼580 °C, semi-ellipsoidal shaped Si-QDs are formed because the precursor supply is a dominant factor.
The self-assembling formation of Si quantum dots (Si-QDs) on as-grown SiO2 layers was shown by controlling the early stages of low-pressure chemical vapor deposition of SiH4. The QD height and radius ...distributions assessed by atomic force microscopy and scanning electron microscopy images revealed that the Si-QDs become hemispherical due to them being rate-limited by aggregation, which reduces the surface energy at substrate temperatures above ∼580 °C. Moreover, at temperatures below ∼580 °C, semi-ellipsoidal shaped Si-QDs are formed because the precursor supply is a dominant factor.
Abstract The lateral growth of Si-quantum dots (QDs) on line-patterned SiO 2 from the thermal decomposition of pure monosilane (SiH 4 ) has been systematically examined. We confirmed that the Si-QDs ...diameter in the line direction of the SiO 2 patterns has the same growth rate as the SiO 2 thin film surface without the line patterns. Moreover, it has been found that in the growth of Si-QDs in the width direction, a surface migration of Si precursors adsorbed from space regions could contribute to dots growth on line-patterned SiO 2 , which results in an elliptical growth. Furthermore, we have demonstrated a one-dimensional arrangement of highly dense-elliptical shaped Si-QDs with high uniformity in size by controlling line width, CVD time, and temperature.
The lateral growth of Si-quantum dots (QDs) on line-patterned SiO2 from the thermal decomposition of pure monosilane (SiH4) has been systematically examined. We confirmed that the Si-QDs diameter in ...the line direction of the SiO2 patterns has the same growth rate as the SiO2 thin film surface without the line patterns. Moreover, it has been found that in the growth of Si-QDs in the width direction, a surface migration of Si precursors adsorbed from space regions could contribute to dots growth on line-patterned SiO2, which results in an elliptical growth. Furthermore, we have demonstrated a one-dimensional arrangement of highly dense-elliptical shaped Si-QDs with high uniformity in size by controlling line width, CVD time, and temperature.
•SBS modifiers enhanced low-temperature crack resistance of asphalt binder.•High strain fatigue life of the SBS modified mastic asphalt mixtures was improved.•The SBS modified mixtures had greater ...flexural toughness than control mixtures.•The SBS modifiers was more substantial in retarding fatigue crack growth.
This study evaluated the fatigue performance of Styrene–Butadiene–Styrene (SBS) modified mastic asphalt mixtures used for bridge deck pavements. The effect of the type and content of newly developed SBS modifiers was investigated using typical binder tests. Four-point bending beam fatigue and indirect strength tests were conducted to examine fatigue and fracture behaviors of the SBS modified mastic asphalt mixtures. The SBS modifiers without CC double bonds enhanced the mechanical properties of the mastic asphalt binder and mixtures: lower stiffness after short- and long-term oxidation, significantly greater fatigue resistance at a higher strain level, and higher crack development resistance.
Abstract Self-aligned Si-quantum-dots (Si-QDs) with an areal density as high as ∼10 11 cm −2 have been fabricated on ultrathin SiO 2 by using a ∼4.5 nm thick poly-Si on insulator (SOI) substrate, and ...controlling low-pressure CVD using monosilane (SiH 4 ), and followed by thermal oxidation. By controlling the thermal oxidation processes of Si-QDs and the poly-Si layer, we have successfully demonstrated the vertical alignment of Si-QDs, where the Si-QDs are also used as a shadow mask of the underlying poly-Si layer. We also demonstrated in-plane alignment of the one-dimensionally self-aligned Si-QDs on line-patterned SiO 2 . In addition, from surface potential measurements by using atomic force microscopy/Kelvin probe force microscopy, we confirmed that the initial surface potential change caused by valence electron extraction from the dots to the tip was stably maintained until ∼120 min, implying the quantum confinement effect at discrete energy levels of the upper and lower-QDs.
Cracking is a major failure mechanism that directly affects the functionality and performance of flexible pavements. The objective of this study is to present the state of knowledge on the use of ...finite element method (FEM) including cohesive zone model (CZM) to simulate cracking failure mechanisms in flexible pavements under field conditions. Based on this review, a knowledge base is established on how FEM can be effectively applied to predict pavement performance against cracking failure mechanisms. Two main approaches are presented in this study. In the first approach, focused finite element (FE) meshes are used to simulate the crack initiation and propagation phases. Focused meshes allow for estimating the J-integral and the stress intensity factor (SIF) through different contour lines. Since the SIF is a measure of the stress and strain environment around the crack tip (a greater SIF indicates a faster rate of propagation), the rate of crack propagation per cycle can be estimated based on empirical equations such as Paris' Law. In the second approach, the propagation of damage is simulated using FE and CZM. This approach allows one to study the loading mechanisms responsible for progressing cracking damage in the pavement structure. In summary, both approaches have merits in modelling cracking in flexible pavements. While focused meshes may be used to predict the number of cycles for crack propagation, CZM may be used to study the controlling stresses and mechanisms responsible for crack propagation.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This study is mainly focused on the evaluation of the effect of Warm Mix Asphalt (WMA) additives on the performance grade ofstraight and polymer modified asphalt binder and the performance of asphalt ...mixtures. In order to analyze these effects, thePerformance Grade (PG) of asphalt binder and the degree of compaction of WMA mixtures with various additives were examinedinitially. Moreover, the degree of compaction was evaluated in field test sections. Lastly, the effect on WMA performance wereevaluated using wheel tracking test and indirect tensile (IDT) strength test for the rutting resistance, moisture susceptibility and crackresistance, respectively. Based on the laboratory and field test results, it can be concluded that WMA additives can affect the PGgrades of conventional but not for polymer modified asphalt binder while viscosity related to mixing and compaction results inconversely. From the field test, the rutting and crack resistances of WMA pavements are higher than HMA pavements in most cases. KCI Citation Count: 1
This study evaluated the effect of the pavement design parameters on the behaviour of orthotropic steel bridge deck pavements under traffic loading using a three-dimensional finite element model. ...Four types of paving materials were considered in this analysis: polymer concrete, epoxy asphalt concrete, polymer-modified stone mastic asphalt concrete and mastic asphalt concrete. The maximum transverse tensile strain was developed at the bottom of the pavement under a tyre of dual tyres or on top of the pavement between two tyres. From the sensitivity analysis, better interface bonding between the deck plate and pavement led to a significant enhancement of bottom-up fatigue cracking resistance, especially for 40-mm-thick pavements. As pavement temperature increased from − 20 to 60°C, critical tensile strain increased significantly, and corresponding locations moved from the bottom to the top of the deck pavement.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
