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The temperature response of pavement is not only crucial for assessing the internal stresses within pavement structures but is also an essential parameter in pavement design. Investigating the temperature response of rubberized concrete pavements (RCP) can support the construction of large-scale rubber concrete pavements. This study constructed a pavement monitoring system based on fiber Bragg grating technology to investigate the temperature distribution, temperature strain, temperature effects, and temperature stress of RCP. The results show that the daily temperature–time history curves of concrete pavement exhibit a significant asymmetry, with the heating phase accounting for only one-third of the curve. The temperature at the middle of RCP is 1.8 °C higher than that of ordinary concrete pavement (OCP). The temperature distribution along the thickness of the pavement follows a "spindle-shaped" pattern, with higher temperatures in the center and lower temperatures at the ends. Additionally, the addition of rubber aggregates increases the temperature strain in the pavements, makes the temperature–strain hysteresis effect more pronounced, and increases the curvature of the pavement slab. However, the daily stress range at the bottom of RCP is approximately 0.7 times that of OCP. [ABSTRACT FROM AUTHOR]

Rubberized cement-based materials are widely utilized because of their good ductility, impact resistance, and fatigue resistance. This research investigated the effect of the rubber aggregates content, particle size of rubber aggregates, and water–cement ratio on the early-age mechanical properties and deformation behaviors of mortar through laboratory tests, and strength reduction coefficient fitting models were established according to the testing results. The results show that the compressive strength growth rate of cement mortar is about 15% slower than that of flexural strength. The existence of rubber aggregates lowers the strength increase rate of mortar. The reduction coefficient of strength decreases with increasing rubber aggregates content and increases with the age of mortar. Increasing rubber aggregates content and decreasing particle size of rubber aggregate can lower the autogenous shrinkage in the initial stage, but the autogenous shrinkage of the later stage increases as the rubber aggregates content increases, with a turning point between 30 h and 50 h. After 3 days, the dry shrinkage of mortar accounts for about 70–80% of the total shrinkage, and it increases with higher rubber aggregate content, smaller particle size of rubber aggregates, and higher water–cement ratios. [ABSTRACT FROM AUTHOR]

In China, airports predominantly utilize airport cement concrete pavement, which inevitably undergoes deterioration in service. To uphold pavement durability and functionality, and ensure aircraft operational safety, prompt repairs of affected areas are imperative. Therefore, ordinary Portland cement mortars were used as the control group to compare and analyze the bonding performances of two common airport pavement repair materials: modified Portland cement mortars and phosphate cement mortars. Meanwhile, through microscopic experiments, the microscopic characteristics of the interfacial transition zone (ITZ) were studied, and the interface bonding mechanism was analyzed. The research results indicate that the interface bonding strength between phosphate cement mortar and old concrete pavement is the highest. This was because the elements in phosphate cement penetrated the old concrete pavement through hydration reactions, forming van der Waals forces and chemical bonding forces. In addition, the research results indicated that the presence of old concrete pavement made the three repair materials produce similar sidewall effects with the old concrete pavement, leading to a low hydration degree of the repair materials. However, the chemical bonding and penetrating structure of phosphate cement compensated for the weakening effect of the ITZ in the repair materials. [ABSTRACT FROM AUTHOR]

Plenty of research has verified that nano-ZnO particles could improve the properties of asphalt, but studies on nano-ZnO-modified asphalt haven't been conducted at the molecular level. Therefore, to investigate the effect of ZnO particles on the properties, structure and morphology of asphalt, the molecular dynamics (MD) methods were carried out. In this study, the models of asphalt, ZnO cluster and ZnO/asphalt blending systems with different particle sizes were built using Materials Studio software. Then, the interaction energies of ZnO/asphalt blending systems under different temperatures were calculated, and the effect of ZnO particles on the modulus and glass transition temperature of matrix asphalt was simulated. The results indicated that the bulk modulus of asphalt increased by ZnO with particle size at 4 Å, 6 Å, 8 Å and 10 Å increased by 15.09%, 12.46%, 10.06% and 8.51%, respectively, which can illustrate that the shear resistance ability and low-temperature properties of asphalt were enhanced. Compared with matrix asphalt, the glass transition temperature of the ZnO/asphalt system decreased by less than 0.1 K, indicating that ZnO's effect on the low temperature of asphalt was not apparent. With the increase of ZnO particle size, the diffusion coefficient decreased sharply. Compared to matrix asphalt, when the particle size increased to 8 Å and 10 Å, the diffusion coefficient decreased by 13% and 22%, respectively. So, in practice projects, to achieve better dispersion of particle materials in base bitumen, a smaller particle size would be recommended. The results of the radial distribution function (RDF) and AFM simulation indicated that ZnO particles changed the micro-structure of asphalt and increased the roughness of the asphalt surface. As a result, ZnO particles bring matrix asphalt better physical properties. [ABSTRACT FROM AUTHOR]

Temperature distribution and the deformation behavior under temperature are important parameters in the design and evaluation of concrete pavements. In this paper, in order to study the horizontal distribution of the temperature effect on rubberized concrete pavement (RCP), the distribution differences of temperature, temperature gradient and strain at different horizontal locations were analyzed based on fiber Bragg grating test technology. The relationships between temperature and strain and between temperature gradient and strain were also investigated. The results show that within a cycle of temperature or temperature gradient change, the time of temperature increase or temperature gradient increase is only 1/4 of the whole cycle, significantly less than the time of the temperature or temperature gradient decrease. Comparing the center, edges and corner of the pavement, the horizontal distribution of temperature and temperature gradients in the RCP is uneven, and the greatest negative temperature gradient is experienced at the corner of the pavement, which is 25 °C·m−1 greater than the temperature gradient at the center. The negative temperature gradient at the corner of the concrete pavement exacerbates the bottom deformation at the center and edge of the pavement, especially in the X-axis direction at the center and in the Y-axis and Z-axis directions at the edge. The relationships between temperature and horizontal strain at the center and edge of the RCP have a significant hysteresis effect and are markedly stronger than those at the corner. Moreover, when the temperature gradient is less than −23.4 °C·m−1 or greater than 14.5 °C·m−1, the curling effect at the edge of the RCP is more obvious. [ABSTRACT FROM AUTHOR]

Dowel bars in concrete pavements can effectively improve the performance of joints as well as the overall performance of pavements. This paper reviewed the mechanical behavior, structural numerical simulation analysis, testing study of doweled joints in concrete pavements, and the research work on the alternative dowel bars. The influences of dowel bar configuration, diameter, spacing, misalignment, rust, and the bonding between the surrounding concrete on the performance of doweled joints were also discussed in this paper. Limitations of theoretical research and test methods were mentioned after reviewing these aspects of dowel bars, indicating the direction for future research on doweled joints in concrete pavements. [ABSTRACT FROM AUTHOR]

Glass fiber geogrid (GFG) is one of the most commonly used materials to mitigate reflective cracks in semi-rigid base asphalt pavement, but there are still some defects in the application of GFG at present. Therefore, GFG was optimized from the perspective of coating treatment. In this paper, the coating materials were firstly optimized from a variety of compounded emulsions (CE) composed of polymer and emulsified asphalt (EA). Then, the properties of the CE and the effect of CE on performances of GFG were studied. The results show that the weighted average particle size, contact angle, viscosity and coating uniformity of polyacrylate compound emulsion (PA-CE) are smaller, higher, higher and better than those of styrene-butadiene compound emulsion (SB-CE), respectively. The GFG impregnated by PA-CE (PA-GFG) has better strength, folding resistance and durability than the GFG impregnated by SB-CE (SB-GFG) and GFG impregnated by EA (EA-GFG). The interlaminar bonding performances and resistance to reflective cracks from flexural-tensile loading of PA-GFG and SB-GFG are not significantly different, while the resistance to reflective cracks from shear loading of PA-GFG is higher than that of SB-GFG. • Glass fiber geogrid was optimized from the perspective of coating treatment. • Coating materials were optimized from compounded emulsions. • Performances of compounded emulsion were tested. • Effect of coating materials on performances of glass fiber geogrid was studied. [ABSTRACT FROM AUTHOR]

This study addresses the challenge of attitude tracking control for a rigid-flexible spacecraft with high-inertia rotating appendages. The Lagrange method was used to establish the kinematic and dynamic models of the spacecraft. The translation and rotation of the spacecraft, vibrations of solar panels, and imbalance caused by the rotating appendages, which cause a complex control problem, were considered. To address the complex control problem, a novel, fast nonsingular integral sliding mode control method is proposed to perform the attitude tracking function of spacecraft. A sliding mode control law was established for the high-inertia appendages to maintain an appropriate angular velocity during rotation. Finally, the effectiveness of the proposed attitude control law was verified by numerical simulations for a spacecraft with high-inertia rotating appendages and symmetrical flexible solar panels. [ABSTRACT FROM AUTHOR]

This study focuses on the attitude control of a flexible spacecraft comprising rotating appendages, magnetic bearings, and a satellite platform capable of carrying flexible solar panels. The kinematic and dynamic models of the spacecraft were established using Lagrange methods to describe the translation and rotation of the spacecraft system and its connected components. A simplified model of the dynamics of a five-degrees-of-freedom (DOF) active magnetic bearing was developed using the equivalent stiffness and damping methods based on the magnetic gap variations in the magnetic bearing. Next, a fixed-time sliding mode control method was proposed for each component of the spacecraft to adjust the magnetic gap of the active magnetic bearing, realize a stable rotation of the flexible solar panels, obtain a high inertia for the appendage of the spacecraft, and accurately control the attitude. Finally, the numerical simulation results of the proposed fixed-time control method were compared with those of the proportional-derivative control method to demonstrate the superiority and effectiveness of the proposed control law.

Background: Opioid titration is necessary to achieve rapid, safe pain relief. Medication can be administered via patient-controlled analgesia (PCA) or by a healthcare provider (non-PCA). We evaluated the efficacy of intravenous PCA versus non-PCA hydromorphone titration for severe cancer pain (≥7 at rest on the 11-point numeric rating scale [NRS])., Patients and Methods: Patients with severe cancer pain were randomized 1:1 to PCA or non-PCA titration, stratified by opioid-tolerant or opioid-naïve status. The PCA pump was set to no continuous dose, with a hydromorphone bolus dose 10% to 20% of the total previous 24-hour equianalgesic (for opioid-tolerant patients) or 0.5 mg (for opioid-naïve patients). For the non-PCA group, the initial hydromorphone bolus dose was identical to that in the PCA group, with the subsequent dose increased by 50% to 100% (for NRS unchanged or increased) or repeated at the current dose (for NRS 4-6). Hydromorphone delivery was initiated every 15 minutes (for NRS ≥4) or as needed (for NRS ≤3). The primary endpoint was time to successful titration (TST; time from first hydromorphone dose to first occurrence of NRS ≤3 in 2 consecutive 15-minute intervals)., Results: Among 214 patients (PCA, n=106; non-PCA, n=108), median TSTs (95% CI) were 0.50 hours (0.25-0.50) and 0.79 hours (0.50-1.42) for the PCA and non-PCA groups, respectively (hazard ratio [HR], 1.64; 95% CI, 1.23-2.17; P=.001). TSTs in opioid-tolerant patients were 0.50 hours (0.25-0.75) and 1.00 hours (0.50-2.00) for the PCA and non-PCA groups, respectively (HR, 1.92; 95% CI, 1.32-2.78; P=.003); in opioid-naive patients, TST was not significantly different for the PCA versus non-PCA groups (HR, 1.35; 95% CI, 0.88-2.04; P=.162). Pain score (median NRS; interquartile range) over 24 hours was significantly lower in the PCA group (2.80; 2.15-3.22) than in the non-PCA group (3.00; 2.47-3.53; P=.020). PCA administration produces significantly higher patient satisfaction with pain control than non-PCA administration (P<.001)., Conclusions: Intravenous hydromorphone titration for severe cancer pain was achieved more effectively with PCA than with non-PCA administration.