Identification of Track Stability Model Parameters Based on Numerical Experiments

In the article, an identification method of railway track stability model parameters based on energy equilibrium is presented by the authors. A study of two parameters directly influencing the continuous welded track (CWR) stability is described by the authors, i.e., the rail-sleeper structure stiffness Bz is considered one beam, and the ballast lateral resistance r0. These parameters were estimated with the use of a numerical model for various railway track types. The adopted concept is based on the assumption that it is possible to determine substitute values for both parameters. Therefore, using one value of both of these parameters, we label them substitute parameters. The assumed numerical model forced lateral displacements of a track section, and, based on the obtained track section displacement results, energy equilibrium was determined. The equilibrium takes into account the work of external load and the bending work of rail-sleeper structure with the substitute stiffness Bz and the ballast deformation work, also with the substitute value of lateral resistance r0 with lateral displacement. The aim is to identify these substitute values to be used for analysing track stability with the semi-analytical model. These analyses are part of the studies related to the development of a method of assessing various methods of increasing track stability.

Revelation of Potentially Seismic Dangerous Tectonic Structures in a View of Modern Geodynamics of the Eastern Caucasus (Azerbaijan)

The stress state of the earth’s crust in the Eastern Caucasus, located in the zone of collision junction of the North Caucasian, South Caucasian, and Central Iranian continental massifs, is a consequence of the inclusion of the Arabian indenter into the buffer structures of the southern framing of Eurasia at the continental stage of alpine tectogenesis. This evidenced from the results of geophysical observations of the structure and seismic-geodynamic activity of the region’s crust. The latter, at the neotectonic stage, was presented as underthrust of the South Caucasian microplate under the southern structures of Eurasia. The analysis and correlation of historical and recent seismic events indicate the confinement of most earthquake foci to the nodes of intersection of active faults with various orientations or to the planes of deep tectonic ruptures and lateral displacements along unstable contacts of material complexes of various competencies. The focal mechanisms of seismic events reveal various rupture types, but in general, the earthquake foci are confined to the nodes of intersection of faults of the general Caucasian and anti-Caucasian directions. Based on the observed weak seismicity, active areas of deep faults were identified, which are accepted as potential source zones.

A Study of the Effects of Geosynthetic Reinforced Soil and Reinforcement Length on GRS Bridge Abutment

The geosynthetic reinforced soil (GRS) bridge abutment with a staged-construction full height rigid (FHR) facing and an integral bridge (IB) system was developed in Japan in the 2000s. This technology offers several advantages, especially concerning the deformation behavior of the GRS-IB abutment. In this study, the effects of GRS in the bridge abutment with FHR facing and the effects of geosynthetics reinforcement length on the deformation behavior of the GRS–IB are presented. The numerical models are analyzed using the finite element method (FEM) in Plaxis 2D program. The results showed that the GRS–IB model exhibited the least lateral displacements at the wall facing compared to those of the IB model without geosynthetics reinforcement. The geosynthetics reinforcement in the bridge abutment with FHR facing has reduced the vertical displacement increments by 4.7 times and 1.3 times (maximum) after the applied general traffic loads and railway loads, respectively. In addition, the numerical results showed that the increase in the length-to-height (L/H) ratio of reinforcement from 0.3H to 1.1H decreases the maximum lateral displacements by 29% and the maximum vertical displacements by 3% at the wall facing by the end of construction. The effect of the reinforcement length on the wall vertical displacements is minimal compared to the effect on the wall lateral displacements.

Critical distance between two irregular adjacent buildings in order to prevent collision during earthquake

The aim of this study is to evaluate the value of suitable distance due to prevent the impact between two irregular adjacent buildings when earthquake is caused to occur large lateral displacement and damage the elements of buildings. For this purpose, by using a mathematical program based on neural network, the number of stories, the period and height of investigated models, PGD, PGV and PGA of earthquake records are defined and the nonlinear lateral displacements of different structures are determined in order to use in the program. Thus, the results of displacements based on all inputs are listed and the minimum critical distance is approximately estimated based on especial regression. For instance, a 3-4 story model is numerically investigated by Tabas earthquake record, which is suggested to provide required gap size about 70 cm. In fact, each model has to observe a 35 cm gap. A newly developed program based on mathematical equations are applied for determining the lateral displacements of each story. A new mathematical formula is proposed by neural network, which shows the least distance between irregular adjacent buildings. For investigating the accuracy of formula, two different ways are performed and the results of analyses confirm suggested equation. For this challenge, a 2-4 story model is considered and three different critical distances are calculated to be 59, 62 and 75 cm which show the last gap size is able to provide safety gap size, determined by suggested formula.

Generalized Link-Cost Function and Network Design for Dedicated Truck-Platoon Lanes to Improve Energy, Pavement Sustainability, and Traffic Efficiency

Recent development of autonomous and connected trucks (ACT) has provided the freight industry with the option of using truck platooning to improve fuel efficiency, traffic throughput, and safety. However, closely spaced and longitudinally aligned trucks impose frequent and concentrated loading on pavements, which often accelerates pavement deterioration and increases the life cycle costs for the highway agency. Also, effectiveness of truck platooning can be maximized only in dedicated lanes; and its benefits and costs need to be properly balanced between stakeholders. This paper proposes a network-design model to optimize (i) placement of dedicated truck-platoon lanes and toll price in a highway network, (ii) pooling and routing of ACT traffic from multiple origins and destinations to utilize these lanes, and (iii) configuration of truck platoons within these lanes (e.g., lateral displacements and vehicle separations). The problem is formulated as an integrated bi-level optimization model. The upper level makes decisions on converting existing highway lanes into dedicated platoon lanes, as well as setting user fees. The lower-level decisions are made by independent shippers regarding the choice of routes and use of platoon lanes vs. regular lanes; and they collectively determine truck traffic in all lanes. Link-cost functions for platoon lanes are obtained by simultaneously optimizing, through dynamic programming, pavement-rehabilitation activities and platoon configuration in the pavement's life cycle. A numerical case study is used to demonstrate the applicability and performance of the proposed model framework over the Illinois freeway system. It is shown that the freight traffic is effectively channelized on a few corridors of platoon lanes and, by setting proper user fees to cover pavement-rehabilitation costs, systemwide improvements for both freight shippers and highway agencies can be achieved.

Unidirectional ion transport mechanism of a light-driven chloride pump revealed using X-ray free electron lasers

Light-driven chloride-pumping rhodopsins actively transport anions, including various halide ions, across cell membranes. Recent studies using time-resolved serial femtosecond crystallography (TR-SFX) have uncovered the structural changes and ion transfer mechanisms in light-driven cation-pumping rhodopsins. However, the mechanism by which the conformational changes pump an anion to achieve unidirectional ion transport, from the extracellular side to the cytoplasmic side, in anion-pumping rhodopsins remains enigmatic. We have collected TR-SFX data of Nonlabens marinus rhodopsin-3 (NM-R3), derived from a marine flavobacterium, at 10 µs and 1 ms time-points after photoexcitation. Our structural analysis reveals the conformational alterations during ion transfer and after ion release. Movements of the retinal chromophore initially displace a conserved tryptophan to the cytoplasmic side of NM-R3, accompanied with a slight shift of the halide ion bound to the retinal. After ion release, the inward movements of helix C and helix G and the lateral displacements of the retinal block access to the extracellular side of NM-R3. Anomalous signal data have also been obtained from NM-R3 crystals containing iodide ions. The anomalous density maps provide insight into the halide binding site for ion transfer in NM-R3.

Mud Motor PDM Dynamics: An Analytical Model

In a fast drilling environment, suchas shale drilling, refining advanced technologies for preventing downhole toolfailures is paramount. Challenges are still very much associated with complex bottom-hole assemblies and the vibration of the drill string when used with a downhole mud motor. The mud positive displacement motor with various lobe configurations and designs becomes an additional excitation source of vibration. Further, it affects the transient behavior of the performance mud motor. Unbalanced force exists because the center ofmass of the motor rotor does not coincide with the axis of rotation.Further, the vector of full acceleration of the center of the rotor can be decomposed into two perpendicular projections—tangent and normal—which aretaken into account and integrated intothe full drill string forced frequency modelas force and displacement at the motorlocation. The paper includes two models, first one to predict the critical speeds and the second one to see the transient behavior of the downhole parameters when the mud motor is used.The model also considers the effect of the stringspeed. The unbalanced force is more pronounced at the lower pair or lobe configuration as compared to the higher pairlobe configuration because of the larger eccentricity. The unbalance is modeled in terms of an equivalent mass of therotor with the eccentricity of the rotor. Also, the analysis provides an estimation of relative bending stresses, shear forces, lateral displacements and transient bit rpm, bit torque, and weightone bit for the assembly used. Based onthe study, severe vibrations causing potentially damaging operating conditionswhen transient downhole forcing parametersare used for the vibration model.It has been found that when a mud motor isused using static forcing parameters may not provide the conservative estimation of the critical speeds as opposed totransient parameters. This is because coupled oscillations fundamentally can create new dynamic phenomena, which cannot be predicted from the characteristics of isolated elements of the drilling system.

Novel Design and Comparison of Structural and Modal Analyses of Auxetic Geometry versus Honeycomb Geometry

Auxetic structures are popular, since they have many applications in defense, textile and sport industries. The advantages of providing comfort and protection to people for the impact energy increase the usability of auxetic structures in these areas. Within the scope of this study, two structures were designed as honeycomb and auxtetic structures with lateral displacements in opposite directions. The auxetic and honeycomb structures were modeled in Ansys software by keeping the boundaries of these two structures close to each other. Structural and modal analysis were applied to these structures and the auxetic structure gave better results in terms of the tensile strength.