Study on Temperature Force Control Mechanism of CRTSⅡ Slab Track: Control Conditions of Temperature Cracking

Diseases such as track slab arching and joint concrete crushing of China Railway Track System (CRTS)II slab track were caused by huge temperature force, which seriously threatens driving safety of trains. In this study, a longitudinal weak connection scheme of CRTSII slab track was proposed to adjust the temperature force in track slab and reduce diseases of longitudinal continuous track slab. This paper focuses on the cracking characteristics of the longitudinal heterogeneous concrete composite structure. The equation which was originally developed to calculate crack width and structure stress under temperature loads, was put forward to consider deformation difference of different elastic modulus. The influence law of various parameters was analyzed. The reinforcement stress and crack width of CRTSII slab track after longitudinal connection weakening were calculated, and the reasonable limit value of tensile force of connection reinforcement and the minimum value of bond resistance of reinforcement in joint position were obtained. The result shows that, in order to reduce the bond resistance between the joint material and the reinforcement, the elastic modulus of the elastic material should be less than 5000 MPa; in order to ensure that the reinforcement does not produce large stress, the elastic modulus of the joint should be greater than 1000 MPa

A Deep-Sea Pipeline Skin Effect Electric Heat Tracing System

In order to ensure deep-water flowline safety, this paper combined the axial temperature distribution model of the submarine pipeline and the distributed parameter circuit model of the skin effect electric heat tracing system such work is conducive to proving that the heating effect of the skin effect electric heat tracing system depends on the distributed circuit parameters and power frequency of the system. Due to the complexity of the power supply device, the frequency cannot be increased indefinitely. Therefore, for the case that the input of the skin electric heat tracing system is constrained, a generalized predictive control algorithm introducing the input softening factor is proposed, and the constrained generalized predictive control strategy is applied to the electric heating temperature control system of the submarine oil pipeline. Simulation results demonstrated that the control quantity of the skin effect electric heat tracing system is effectively controlled within a constraint range, and also the values of heating power and power frequency are obtained by theoretical calculations rather than empirical estimations. Moreover, compared with the conventional control algorithm, the proposed constrained generalized predictive algorithm unfolds more significant dynamic response and better adaptive adjustment ability, which verifies the feasibility of the proposed control strategy. Document type: Articl

Effectiveness of the Different Eutectic Phase-Change Materials in Cooling Asphalt Pavement

Choosing a Phase-Change Material (PCM) Adapted to the Specific Phase-Change Temperature (Tm) Required for Each Temperature Condition is of Utmost Importance in Cooling Pavements. Eutectic Phase-Change Materials (EPCMs) Realize the Customization of the Desired Tm and Reduce the Difficulty of Matching PCMs. This Work Aims to Investigate the Effectiveness of a Group of Binary/ternary EPCMs with Tm Ranging from 30 to 60 ℃ and Melting Enthalpies of Around 200 J/g as Thermal Regulation Components for Different Asphalt. to Achieve This Goal, the Thermal and Rheological Properties of Phase-Change Asphalt Binders (PCAB) Were Evaluated by Differential Scanning Calorimeter, Thermogravimetric, Fourier Transform Infrared, and Multiple Stress Creep and Recovery Tests. the Results Showed that PCAB with Latent Heat Improved the Specific Heat Capacity, Which Brought a Maximum Temperature Lag of 134.5 Min and a Maximum Temperature Difference of 11 ℃. Similarly, the PCAB Remained Chemical Stability, and its Thermal Stability Complied with the Construction Temperature Specifications. However, the Recrystallization of EPCMs Was Impeded by the Molten Asphalt Binder Matrix, Resulting in a Significant Reduction in Both the Tm and Enthalpy. Therefore, These Reductions Should Be Taken into Consideration When Choosing an EPCM. Additionally, as Liquid EPCM Softens the Binder, the Absence of Elasticity in Solid EPCMs Renders the Binder Stiff, Thus Reducing its Resistance to Deformation. These Impacts Were Particularly Noticeable in Styrene-Butadiene-Styrene Modified Asphalt Due to the Polymer Network Being Dissolved by Liquefication-EPCMs. to Sum Up, EPCMs with a Higher Tm (40–60 ℃) May Decrease their Negative Impact on Deformation Resistance, Such as Palmitic Acid-Myristic Acid-Methyl Stearate Mixtures

Elevation as a selective force on mitochondrial respiratory chain complexes of the Phrynocephalus lizards in the Tibetan plateau

Animals living in extremely high elevations have to adapt to low temperatures and low oxygen availability (hypoxia), but the underlying genetic mechanisms associated with these adaptations are still unclear. The mitochondrial respiratory chain can provide >95% of the ATP in animal cells, and its efficiency is influenced by temperature and oxygen availability. Therefore, the respiratory chain complexes (RCCs) could be important molecular targets for positive selection associated with respiratory adaptation in high-altitude environments. Here, we investigated positive selection in 5 RCCs and their assembly factors by analyzing sequences of 106 genes obtained through RNA-seq of all 15 Chinese Phrynocephalus lizard species, which are distributed from lowlands to the Tibetan plateau (average elevation >4,500 m). Our results indicate that evidence of positive selection on RCC genes is not significantly different from assembly factors, and we found no difference in selective pressures among the 5 complexes. We specifically looked for positive selection in lineages where changes in habitat elevation happened. The group of lineages evolving from low to high altitude show stronger signals of positive selection than lineages evolving from high to low elevations. Lineages evolving from low to high elevation also have more shared codons under positive selection, though the changes are not equivalent at the amino acid level. This study advances our understanding of the genetic basis of animal respiratory metabolism evolution in extreme high environments and provides candidate genes for further confirmation with functional analyses

Influence of macrobenthos ( Meretrix meretrix Linnaeus ) on erosion‐accretion processes in intertidal flats: A case study from a cultivation zone

The activity of benthic organisms can strongly influence sediment dynamics in anintertidal flat. However, few studies have conducted a quantitative assessment of the effect of benthic organisms on erosion-accretion processes under field conditions. The aim of this study was to quantify the effects of the benthic clam Meretrix meretrix Linnaeus on bed erodibility and sediment erosion- accretion processes in an intertidal flat. Within the cultivation zone atsite A, M. meretrix is present in large numbers (up to 137 individuals/m2). On the other hand, site B is located outside the cultivation zone. At this site, which is only 500 m away from site A alongshore, M. meretrix forms a sparse population with only 3.7 individuals/m2. The results showed that the critical shear stress for erosion, denoted by τce, was 0.22 and 0.32 N/m2 at sites B and A, respectively, and the magnitudes of bed-level change were significantly higher at site A than site B. These results reveal the large effect of M. meretrix on decreasing τce, augmenting the erosion rate when the bed shear stress due to combined currents and waves, denoted by τcw, was higher than τce, and conversely enhancing the accretion rate when τcw < τce. The changes induced in these parameters are likely to have a large impact on model predictions of bed erodibility, sedimentary processes, and morphological evolution. Thus, integrated field measurements of hydrodynamic and bed-level changes, accompanied by simultaneous biological sampling, may help to improve the parameterization of hydro-sedimentary and morphodynamic models for shallow-water environmentsFil: Shi, Benwei. Tongji University; República de China. East China Normal University; República de ChinaFil: Pratolongo, Paula Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; ArgentinaFil: Duy, Yongfen. Nanjing Normal University; República de ChinaFil: Li, Jiasheng. Nanjing Normal University; República de ChinaFil: Yang, S.L.. East China Normal University; República de ChinaFil: Wu, Jihua. Fudan Universit. Institute of Biodiversity Science; República de ChinaFil: Xu, Kehui. State University of Louisiana; Estados UnidosFil: Wang, Ya Ping. East China Normal University; República de Chin