Search

Slippage cracking in asphalt overlays occurs because of bonding failure between the asphalt concrete and Portland cement concrete layers. A direct shear test was adopted to simulate common and critical bonding failures. The effects of temperature and tack coat have already been studied by previous researchers; however, the effects of texture have not been sufficiently considered. In this study, clamping shear strength was used to characterize the pure shear strength of the pavement. It is defined as the difference between the total shear strength and plane shear strength. The results indicated that the interlayer behaved in an elastic manner at lower temperatures, generating brittle failures with cracking, whereas viscoelastic behavior dominated at higher temperatures, producing ductile failure that led to slippage at the interface layer. The surface texture effects can be quantitatively characterized using the clamping shear strength. In addition, the clamping shear strength can be used to optimize the asphalt mixture to enhance the bonding performance. Key words: asphalt concrete (AC) overlay, interlayer bonding failure, clamping strength, texture, Portland cement concrete (PCC) rehabilitation. La fissuration parabolique de glissement des couches d'asphalte se produit a la suite d'une defaillance de l'adherence entre les couches de beton asphaltique (BA) et le beton de ciment Portland (BCP). Un essai de cisaillement direct a ete adopte pour simuler la defaillance d'adherence commune et critique. Les effets de la temperature et de la couche d'adherence ont deja ete etudies par des chercheurs precedents, mais les effets de la texture n'ont pas ete suffisamment pris en compte. Cette etude a utilise la resistance au cisaillement de serrage pour caracteriser la resistance au cisaillement pure dans la chaussee. Elle est definie comme la difference entre la resistance totale au cisaillement et la resistance au cisaillement normale. Les resultats ont montre que l'inter couche s'est comportee de maniere elastique a des temperatures plus basses, generant des ruptures fragiles avec fissuration, tandis que le comportement viscoelastique a domine a des temperatures plus elevees, produisant une rupture ductile qui conduit au glissement a la couche d'interface. Les effets de texture de surface peuvent etre caracterises quantitativement en utilisant la resistance au cisaillement de serrage, et cette resistance peut etre utilisee pour optimiser le melange d'asphalte dans l'amelioration des performances de l'adherence. [Traduit par la Redaction] Mots-cles : rechargement de beton asphaltique (BA), defaillance de l'adherence entre les couches, force de serrage, texture, readaptation du beton de ciment Portland (BCP)., Introduction Asphalt concrete (AC) overlay is one of the most typical pavement maintenance strategies used in Portland cement concrete (PCC) pavements to extend their service life. The life of an [...]

Reflection cracking is a critical issue in asphalt overlay pavement. Temperature variation and traffic loading are the main fracture modes acting on the material. In this paper, a multi-modal overlay tester is proposed for the evaluation of the reflection cracking resistance of an asphalt mixture, an approach that simulates three loading modes on asphalt specimens. A fine dense-grade hot mix asphalt is used as the test specimen and subjected to different loading conditions such as single Mode I, II, and III loading simulations and combined I+II and I+II+III loading simulations. Results show coefficients of variation (CVs) of 2.5%, 10.3%, and 7.4% for the Mode I, II, and III loading simulations, respectively. Furthermore, the [beta] coefficient, with a CVof 7%, is used to represent the crack resistance of the asphalt mixture. Finally, the crack propagation occurs rapidly when subjected to tension and lateral displacement prior to repeated traffic loading simulations. Key words: fatigue test, mixed loading mode, reflection cracking, asphalt overlay tester. La fissuration par reflexion est un probleme critique pour les chaussees asphaltees. La variation de temperature et la charge de roulage sont les principaux modes de rupture agissant sur le materiau. Dans le present document, un appareil d'essai de revetement multimodal est propose pour l'evaluation de la resistance a la fissuration par reflexion d'un melange d'asphalte, une approche qui simule trois modes de chargement sur des echantillons d'asphalte. Un asphalte melange a chaud a base d'agregat a haute densite est utilise comme echantillon d'essai et soumis a differentes conditions de chargement, comme des simulations de chargement en mode I, II et III simples et des simulations de chargement combinees I+II et I+II+III. Les resultats montrent des coefficients de variation (CV) de 2,5, 10,3 et 7,4 % pour les simulations de chargement des modes I, II et III, respectivement. De plus, le coefficient [beta], avec un CV de 7 %, est utilise pour representer la resistance a la fissuration du melange d'asphalte. Enfin, la propagation des fissures se produit rapidement lorsqu'elles sont soumises a une traction et a un deplacement lateral avant les simulations repetees de charges de roulage. [Traduit par la Redaction] Mots-cles : essai de fatigue, mode de chargement mixte, fissuration par reflexion, appareil d'essai de revetement bitumineux., Introduction Reflection cracking is a major problem that needs to be overcome in asphalt overlays on Portland cement concrete (PCC) pavement. Accordingly, the design of an asphalt overlay requires accurate [...]

The historical management of underground utilities such as communication lines, water and sewage pipes, and power lines is essential for their effective use. However, due to the nature of the buried facilities, detecting and tracking them are challenging, although various solutions are difficult to apply in the field, especially optical cables, which are mainly used for communication, making it more difficult to apply existing solutions. There has been limited research on the practicalities of solutions, especially on multilayer structures such as road pavements. Based on a literature review, we selected ultra-high-frequency radio frequency identification (UHF RFID), which is least affected by performance degradation or interference due to batteries. We experimented to identify the signal attenuation based on the medium by controlling the materials and moisture used in the road pavement as variables. The signal reached a depth of 68 cm and this was possible under conditions of asphalt and subgrade soil. In a comparative experiment for each variable, we recognized tags of sand and coarse aggregate up to a depth of 70 cm. When the moisture was considered, the signal attenuation difference was 1.8 dBm for each level. Based on the experimental results of this study, it was confirmed that UHF RFID can be used as a marker sensor to be attached to utilities installed under the road pavement. Depending on the structure and material of the pavement, the signal is sufficiently transmitted up to 40–50 cm, which is the target installation depth of the communication line. [ABSTRACT FROM AUTHOR]

Permeable pavement is widely used to improve the water circulation system in urban areas. The advantages of using permeable pavement are the storage of rainwater, reduction of runoff, out-flow delay, and reduction of peak discharge. The outflow characteristics of different types of permeable pavements are explained by runoff coefficients, which define the relationship between runoff and infiltration rate. This study presents a model of cumulative outflow with respect to time explaining the discharge characteristics of permeable pavement. The model can be used to explain storage capacity, delay time, peak discharge rate, and outflow of pavement structure by accumulating total discharge at the surface and subsurface relative to time. For further verification of the model, a rainfall simulation experiment was performed in the field. Based on the data analysis through the developed model, the advantages of different permeable pavements can be characterized. Key words: permeable pavement, pavement storage capacity, cumulative water flow, time and space model. Les chaussees permeables sont utilisees pour ameliorer le systeme de circulation d'eau dans les zones urbaines. Elles presentent les avantages suivants : l'entreposage de l'eau de pluie, la reduction du ruissellement, le delai des ecoulements et la reduction du debit de pointe. Les caracteristiques des rejets pour divers types de chaussees permeables sont expliquees en tant que coefficient de ruissellement, lequel definit la relation entre le ruissellement et le taux d'infiltration. Cette etude presente un modele de rejet cumulatif qui tient compte du temps, expliquant les caracteristiques de decharge des chaussees permeables. Le modele peut servir a expliquer la capacite d'entreposage, le delai, le debit de pointe et le rejet par la chaussee en accumulant, dans le temps, la decharge totale a la surface et dans la sous-surface. Pour pousser la verification du modele, une experience de simulation de precipitations a ete realisee sur le terrain. En se basant sur l'analyse des donnees par le modele mis au point, il est possible de caracteriser les avantages des diverses chaussees permeables. [Traduit par la Redaction] Mots-cles: chaussee permeable, capacite d'entreposage des chaussees, debit d'eau cumulatif, modele de temps et d'espace., 1. Introduction As urbanization continues, the convenience of the living environment has improved with efficient land utilization. The water circulation system of the city changes as ground coverage increases. The [...]

The primary objective of the present study is to assess the use of the maturity method to determine the joint sawing window and the traffic opening time on whitetopping construction in Korea. To determine the joint sawing time, it is necessary to determine the minimum strength not to have raveling and to identify the safe time of drying shrinkage. The present study found that the minimum compressive strength for joint sawing was 4.41 MPa (45 kg/[cm.sup.2]) and drying shrinkage occurred just after the concrete temperature peaked. The Nurse-Saul function was used for determining the joint sawing window and the traffic opening time because it better predicted in-place strength. The present study determined that the joint sawing window ranged from 210°C x h to 310°C x h (actual time of 6.5 to 9 h) and that the traffic opening time was after maturity values reached 390°C x h for the mix at 20°C. Key words: maturity, Nurse-Saul function, Arrhenius equation, whitetopping. Le principal objectif de la presente etude est d'examiner l'utilisation de la methode d'evaluation de la maturite afin de determiner la fenetre de coupage du joint a la scie et le moment d'ouverture a la circulation apres un resurfacage sur asphalte en Coree. Pour definir le moment de coupage du joint a la scie, il faut determiner la resistance minimale de maniere a ne pas provoquer d'arrachement et a identifier le temps adequat de retrait de sechage. La presente etude a decouvert que la resistance en compression minimale pour la coupe du joint a la scie etait de 4,41 MPa (45 kg/[cm.sup.2]) alors que le retrait de sechage est survenu une fois que le beton avait atteint sa temperature maximale. La fonction Nurse-Saul a ete utilisee pour determiner la fenetre de coupage du joint a la scie et le moment d'ouverture a la circulation parce qu'elle predisait mieux la resistance en place. Cette etude a determine que la fenetre de coupage du joint a la scie etait de 210°C-heure a 310 °C-heure (temps reel de 6,5 a 9 heures) et le moment d'ouverture a la circulation se produisait une fois que les valeurs a maturite avaient atteint 390 °C-heure pour le melange a 20°C. Mots-cles : maturite, fonction Nurse-Saul, equation d'Arrhenius, resurfacage sur asphalte. [Traduit par la Redaction], Introduction The maturity method was first applied to whitetopping construction in Korea. Because there were no reported cases of the application of maturity methods to whitetopping construction, a laboratory test [...]

The objective of this research is to evaluate how the physical properties and thickness of asphalt pavements influence behaviors of ultra thin whitetopping (UTW). The results of the three-dimensional finite-element method reveal that properties of asphalt and concrete layers, bonding between the two layers, and temperature strongly affect the distress of UTW. Based on results of FEM analysis, a wheel tracking device called the 'heart wheel load simulator (HWLS)' was developed and used to perform an experiment to observe behavior variation in accordance with asphalt and concrete layer thicknesses as well as temperature. The results of HWLS simulation show that the effect of temperature is not significant and the increase of the tensile strain with the increase of a load is relatively small for a 100 mm concrete layer, as compared to a 50 mm concrete layer. In addition, for a 50 mm concrete layer with a less than 150 mm asphalt layer, the increased ratio of the tensile strain at the bottom of the concrete slab is significantly higher. Therefore, this research recommends that an at least 150 mm asphalt layer after milling be required in order to apply UTW safely. DOI: 10.1061/(ASCE)0733-947X(2006) (880) CE Database subject headings: Rehabilitation; Asphalt pavements; Simulation.

Concrete block pavement is used as a modern pavement type owing to its economic benefits. The physical properties, mechanical properties, and functional characteristics of bedding sand and joint sand, the main components of concrete block pavements, should be accurately understood. Owing to the discontinuous structure of these pavements, load transfer efficiency (LTE) is the most important index from the perspective of performance. The factors that affect LTE are bedding sand (type, grading, and thickness), joint sand (type and grading), and concrete block (shape and pattern). Therefore, the optimal design for concrete block pavements can be achieved by analyzing each factor. In this study, three types of sand (river, quartz, and manufactured) were selected to examine the mechanical properties via direct transfer experiments. It was observed that the shear strength of river sand was the highest. It was also found that the difference between the shear strength and the internal friction angle (according to the content of 0.6 mm in the grading of bedding sand) was not large, and the shear strength and the friction angle increased as the content increased to 0.075 mm. In addition, the load transfer characteristics of the joint and rotational interlocking of the block were evaluated through a non-destructive test using the degree of joint filling, block shape, and construction pattern as variables. As a result, the degree of joint filling had the greatest effect on the load transfer characteristics of the joint and rotational interlocking of the block. The effect of the block shape was larger than that of the construction pattern. When a heavy load is applied, the LTE between blocks must be maintained at 50% or more, and the rotation of blocks at 0.6° or less, if 75% or more of the joint must be filled for preventing excessive vertical deformation. [ABSTRACT FROM AUTHOR]

Intramolecular cyclization of 1,1‐diisopropyl‐ or diphenyl‐bis(phenylethynyl)‐silanes (2a and 2b) followed by bromination or trimethylsilylation were carried out to yield 1,1‐diisopropyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐dibromo‐siloles (3a and 3b) and 1,1‐diisoproyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐bis(trimethylsilyl)‐siloles (4a and 4b), respectively. The structures of 3a,b and 4a,b were confirmed using 1H, 13C, and 29Si NMR as well as FTIR spectroscopy. The absorption bands of the siloles 3a,b and 4a,b in THF were measured at 303–325 nm with the molar absorptivities of 1.85 × 103 ~ 2.18 × 103 cm−1·M−1. The excitation bands were measured at 347–376 nm and the emission peaks were measured at 409–445 nm. Cyclic voltammograms of 3a and 3b indicated oxidation peaks at 0.90 and 0.80 V and reduction peaks at −1.20 and −1.20 V, respectively. The cyclic voltammograms of 4a and 4b indicated two oxidation peaks between −0.05 and −0.95 V and two reduction peaks between −0.10 and −0.93 V, respectively. Compound 4a exhibits a better long cycle performance by almost 1000 cycles as compared that of 3a and 4b. The rate performance test of the anodes Li‐3a and Li‐4a exhibited better performance properties at various C rate than Li‐4b. According to discharge–charge curves, 4a shows one plateau at approximately 0.58 V of the first discharge curve and the initial discharge specific capacity of 972 mAh/g. The electrochemical impedance spectroscopy of 4a indicates low charge transfer resistance, good conductivity of the electrolyte, and fast chemical adsorption/desorption rate of electrolyte ions on electrode surface, due to the electronic structure of 4a. [ABSTRACT FROM AUTHOR]

In South Korea, the performance of continuously reinforced concrete pavement (CRCP) has been better than that of jointed concrete pavement (JCP). However, most of the Portland cement concrete (PCC) pavements in South Korea have been JCP, primarily due to the difficulty in providing extra space along the edge of the pavement needed for concrete delivery in CRCP construction. In a tube-feeding method (TFM), concrete can be supplied from the front of a paver, which could facilitate CRCP construction without extra space needed. In the present study, efforts were made to improve the capability of TFM in placing longitudinal steel at correct elevations, which resulted in the development of tube feeding equipment (TFE). Field testing results showed that the key to ensuring steel placement at correct elevations was to keep longitudinal steel in adequate tension. The distance from the back of the tubes and the front of the mould, up to 1500 mm, did not have substantial effects on the steel settlement. To evaluate the viability of CRCP construction with TFE, a 400 m long CRCP section with 300 mm slab thickness and 8.2-m width was constructed and performance monitored. [ABSTRACT FROM AUTHOR]

Byline: Do Hyun Ahn, Jae Kyeong Kim, Il Young Choi, Yoon Ho Cho With the advance of e-commerce, the importance of recommender systems grows larger than before. Collaborative filtering is the most successful recommendation method, but its widespread use has exposed some problems such as sparsity and scalability. To overcome such limitations, this paper proposes hybrid recommendation methodologies based on web usage mining and dimensionality reduction techniques to enhance the recommendation quality and performance of current collaborative filtering-based recommender systems. Web usage mining populates the rating database by tracking customers' shopping behaviours on the web, thereby leading to better quality recommendations. The product taxonomy and SVD (Singular Value Decomposition) are used to improve the performance of searching for nearest neighbours through dimensionality reduction of the rating database. Experiments on real e-commerce data show that the proposed methodologies provide higher quality recommendations and better performance than existing collaborative filtering methodologies.

Abstract: We report the ionic conductivity studies of three different Ruddlesden‐Popper layered perovskite (RP‐LP) materials (Li2SrTa2O7, Li2SrNb2O7, and Li2CaTa2O7) in composites with poly (ethylene oxide) (PEO). For the first time, the lithium‐ion conduction pathway in the RP‐LP materials, of n=2 in AnA′BnO3n+1 general crystal structure, have been studied by using bond valence sum mapping. The results show a two‐dimensional lithium‐ion pathway. The temperature dependence of the conductivity is modelled by using a Vogel−Tamman−Fulcher (VTF)‐type relationship for PEO RP‐LP and pure PEO samples. The PEO RP‐LP composites deliver ionic conductivities in the range of 3.32 to 4.09×10−06 σ cm−2 at 80 °C, and their corresponding activation energies range from 6.37 to 7.01 kJ mol−1 at the calculated temperature slope range of 50 to 80 °C. They also deliver appreciable lithium transference numbers in the range of 0.20 to 0.58 at 30 °C and an excellent wide potential window stability of 4 V. [ABSTRACT FROM AUTHOR]

Concrete block pavement (CBP) is distinct from typical concrete or asphalt pavements. It is built by using individual blocks with unique construction patterns forming a discrete surface layer to bear traffic loadings. The surface structure of CBP varies depending on the block shapes and construction patterns, so it is hard to apply a general equivalent elastic modulus estimation method to define the surface structural strength. In this study, FEM analysis and dynamic loading test were carried out to develop a deflection prediction model for CBP considering the block shapes and construction patterns. Based on the analysis results, it was found that block shapes did not have much effect on load distribution, whereas construction patterns did. By applying the deflection prediction model to the rutting model for CBP proposed by Sun, the herringbone bond pattern showed the best performance comparing with stretcher bond or basket weave bond pattern. As the load repetition increased to 1.2 million, the rutting depth of CBP constructed by herringbone bond pattern was 2 mm smaller than those constructed by the other two patterns. [ABSTRACT FROM AUTHOR]

UV/ozone treated (UVO-treated) TaS2 and non-treated TaS2 nanosheets are introduced into organic photovoltaic cells (OPVs) as hole extraction layers (HEL) and electron extraction layers (EEL). TaS2 nanosheets are obtained via ultrasonic vibration and size-controlled by centrifugation. Atomic force microscopy (AFM) images reveal that the thickness and lateral size of TaS2 nanosheets are approximately 1 and 70 nm, indicating that uniform and ultrathin TaS2 nanosheets are obtained. The work function of TaS2 increases from 4.4 eV to 4.9–5.1 eV after applying UVO treatment by forming Ta2O5. In addition, the power conversion efficiencies of normal OPV with UVO-treated TaS2 and inverted OPV with TaS2 are 3.06 and 2.73%, which are higher than those of OPV without TaS2 (1.56% for normal OPV and 0.22% for inverted OPV). These results indicate that TaS2 is a promising material for HEL and EEL layers in OPVs. [ABSTRACT FROM AUTHOR]

Abstract: An ultraselective and ultrasensitive trimethylamine (TMA) sensor was achieved using MoO3 nanoplates-prepared by ultrasonic spray pyrolysis followed by a heat treatment at 450°C. The small and thin MoO3 nanoplates with gas-accessible structures showed an unusually high response to 5ppm TMA (ratio of resistance to air and gas=373.74) at 300°C with detection limit as low as 45ppb. Moreover, the ratios of the cross-responses to interfering gases (i.e., 5ppm C2H5OH, CO, CH4, C3H8, H2, and NO2) to the response to 5ppm TMA were extremely low (0.008–0.016). The source of the ultraselective and highly sensitive detection of TMA with negligible interference from other gases is discussed with respect to the acid/base properties, size, and morphology of the MoO3 sensing materials. [Copyright &y& Elsevier]

Abstract: WO3 hollow spheres were prepared by ultrasonic spray pyrolysis of a citric-acid-containing precursor solution, and their trimethylamine-sensing characteristics were investigated. The WO3 hollow spheres showed a high response to 5ppm of trimethylamine (R a/R g =56.9, R a: resistance in air, R g: resistance in gas) with low cross-responses to 5ppm C2H5OH, CO, CH4, C3H8, H2, NH3, and NO2. The high gas response observed was explained by the effective electron depletion of small primary particles and the enhanced gas accessibility of hollow structures with thin and porous shells. The enhanced trimethylamine selectivity was discussed in terms of the interaction between basic analyte gas and acidic sensing materials. [Copyright &y& Elsevier]