Column Axis Research Articles

Моделирование поворотного механизма гидроманипулятора лесовозного автомобиля

The importance of loading and unloading operations in the technological process of wood hauling by timber trucks, as well as the need to improve the design of hydraulic manipulators, are considered. The most rational ways to increase the efficiency of their functioning are given. The disadvantages of traditional designs of hydraulic manipulator rotary mechanisms based on rack-and-pinion gears are presented. An improved design of the crank rotary mechanism of the hydraulic manipulator column from six hydraulic cylinders is proposed. The research methodology is based on the use of mathematical modeling. It has been revealed that the accumulated energy for one braking cycle when moving the load is about 1442 J. Considering that timber loading is carried out at a height of approximately 2 m, the recovery system allows approximately 12 % of the rotation energy to be directed to the load lifting operation. Over the entire range of change in the angle of the end of rotation, the recovered energy varies by only 7.1 % – from 1340 to 1442 J, and the load swing amplitude – by 1.2 % – from 0.336 to 0.340 m. It has been determined that with an increase in the length of the guide, the recovered energy decreases slightly – from 1564 to 1428 J (by 8.7 %) – and the load swing amplitude – from 0.344 to 0.339 (by 1.5 %). It has been found that over the entire angular range, the recovered energy varies from 1399 to 1442 J (by 3 %), and the load swing amplitude – from 0.3380 to 0.3393 m (by 0.4 %). The angular unevenness of the recovery efficiency indicators is no more than 3 %. To study the influence of the parameters of the crank rotary mechanism of the hydraulic manipulator column on the efficiency of energy recovery, a multifactor optimization problem has been solved. It has been established that the optimal value of the distance from the crank axis to the movable axes of the hydraulic cylinders of the rotary mechanism of the hydraulic manipulator column is 0.23–0.25 m, the optimal value of the displacement of the crank axis relative to the axis of the manipulator column is 0.17–0.18 m. At the same time, the recovered energy for 1 cycle of load moving is at least 1500 J, and the amplitude of the load swing is no more than 0.35 m.

Ensemble surrogate modeling of advective-dispersive transport with intraparticle diffusion model for column-leaching test

Column-leaching tests are a common approach for assessing the leaching behavior and resulting environmental risks of contaminated soils and waste materials, which are frequently reused for various construction purposes. The observed breakthrough curves of the contaminants are influenced by the complex dynamics of solute transport and kinetic inter-phase mass transfer. Disentangling these interactions necessitates numerical models. However, inverse modeling and sensitivity analysis can be time-consuming, especially when sorption kinetics are explicitly described by intraparticle diffusion, which requires discretizing the domain both in the flow direction along the column axis and inside the grains. To circumvent the need for such computationally intensive models, we have developed two different ensemble surrogate models. These models employ two separate ensemble methods: random forest stacking and inverse-distance weighted interpolation. Each method is applied to base surrogate models that cover different parts of the parameter space. The base surrogate models use the method of Extremely randomized Trees (ExtraTrees). The defined parameter range is based on the German standard for column-leaching tests. To optimize the base surrogate models, we utilized adaptive-sampling methods based on three distinct infill criteria: maximizing the expected improvement, staying within a certain Mahalanobis distance to the best estimate (both for exploitation), and maximizing the standard deviation (for exploration). The ensemble surrogate model demonstrates excellent performance in emulating the behavior of the original numerical model, with a relative root mean squared error of 0.09. We applied our proposed ensemble surrogate model to estimate the complete posterior parameter distribution using Simulation-Based Inference, specifically Neural Posterior Estimation, to determine the full parameter distribution conditioned on copper-leaching data from two different soils. Samples drawn from the posterior distribution align perfectly with the observed data for both the surrogate and original models.

A Donor-Acceptor Molecular Octopus and the CLICK Procedure in Columnar Liquid Crystal Phases.

Two star-shaped mesogens with a (meso-tetraphenylporphinato) zinc (II) core and bithiophene conjugated arms with 3,4,5-trisdodecyloxyphenyl periphery were synthesized. One of these molecules was decorated with four fullerenes via an aliphatic spacer. This is the sterically overcrowded compound with an octapodal morphology. The other star lacks the fullerenes and provides free space between the conjugated arms. This mesogen does not aggregate in solution, but in solid state it forms a hexagonal columnar and a highly ordered oblique helical columnar phase, while the octopus molecule assembles in an amorphous solid. Photophysical studies of the octapodal compound in solution and the solid thin film reveal the formation of J-type aggregates, in which the interaction between donors (porphyrin) and acceptors (fullerene) dominates leading to absorption bands in the NIR region of the spectra. The mixture of both compounds results in a self-assembly which is called the Click procedure. Fullerenes of the octopus nanosegregate in the pockets of the star mesogens generating hexagonal columnar structures with a regular stacking along the columnar axis. Thus providing free space is a tool to control the competition between supramolecular interactions and nanosegregation. Such liquid-crystalline donor-acceptor structures may play a role in future LC photovoltaic applications.

The influence of an innovative trigger obtained by zonal appropriate annealing of the walls in a columnar passive energy absorber on the achieved crashworthiness indicators - experimental study

The crashworthiness indicators are a key parameter for assessing the effectiveness of energy absorbers and these in turn are highly dependent on the initial phase of the crumple process and triggering mechanism. In classical designs, indentations or holes are made at a specific location to improve the triggering performance, however, the effects are limited and often unsatisfactory. This paper proposes an innovative, original solution for a column energy absorber that significantly improves the triggering parameters and relies on the introduction of smooth changes in material properties along the column axis through the use of specially localized annealing and cooling with specific parameters in its manufacturing process. The veracity of the idea presented was warranted by an experiment from which the characteristics of crushing force vs. shortening were obtained, which in turn were used to calculate crashworthiness indicators. Results confirm extremely good energy-absorbing properties of the proposed solution compared to the classic ones.

Fire performance of steel reinforced concrete column to reinforced concrete beam planar frames: Experiment

This paper investigates the fire performance of large-scale steel reinforced concrete (SRC) column to reinforced concrete (RC) beam planar frames by a series of fire resistance tests. The testing parameters included beam load ratio, column steel ratio and column dimension. The test results indicated that, in fire condition, the SRC column to RC beam frame exhibited two primary failure modes: beam shear failure and column compression failure. In the case of beam shear failure, the fire resistance of frame specimens increased as the beam load decreased. In the scenario of column compression failure, out-of-plane failure occurred due to the weak axis of the SRC column being located outside the frame plane. Concurrently, the RC beam displayed significant shear deformation at the ends and notable bending deformation in the middle. The test results indicated that the column cross-sectional size notably influenced the fire resistance of SRC column to RC beam frame, however, the influence of column steel ratio was minimal.

Cogwheel Mechanism of Helical Self-Organization is Thermodynamically Controlled, Self-Repairing, and Universal.

The cogwheel mechanism of helical self-organization, reported by us, generates columns with the alkyl chains of their components parallel to the column axis. This mechanism disregards the enantiomeric purity of constituents and, under suitable design, provides the fastest rate of helical self-organization. Here, we investigate the supramolecular structure of a thermodynamically controlled helical self-organization system. Unexpectedly, we found that this system follows a cogwheel mechanism of helical self-organization that does not contain the two key parameters of the cogwheel mechanism: the length of the alkyl group of the self-assembling dendron identical to the helical half-pitch (hhp) of the column and the presence of chiral branches pointing toward the column center. Unpredictably, we uncovered that the presence of chiral branching points and strict alkyl chain lengths is not a requirement of the cogwheel mechanism. A self-repairing process provides access to a constant hhp via a shorter and longer alkyl chain length than the originally exact demanded value, which together with the lack of branching point(s) demonstrates the universality of the cogwheel mechanism of helical self-organization. Applications derived from this concept are envisioned.

Comparative anatomy and evolution of the atlantoaxial complex in the fossorial lineage Amphisbaenia (Squamata: Lacertoidea).

The atlas and axis are the first two vertebrae from the cervical series; these two vertebrae are responsible for neck flexion, extension, and rotation movements, while providing insertion points for muscles and tendons. Amphisbaenia is a group of fossorial squamates known for having four distinctive head shapes, which are related to different excavation methods. However, little is known about the relationship between these different digging patterns and the anatomy and evolution of the atlantoaxial complex. In this study, we used computed microtomography data to describe in detail of the atlantoaxial complex for 15 species, belonging to all six current families of Amphisbaenia. Furthermore, we evaluate evolutionary scenarios of selected characters related to the atlantoaxial complex in the most recent phylogeny for Amphisbaenia, using the criteria of parsimony and maximum likelihood. Our results indicate that the evolutionary pattern of the atlantoaxial complex presents a diversification in its morphology that is not always correlated with the shape of the head. This analysis reinforces the hypothesis of remarkable morphological convergences in the evolutionary history of Amphisbaenia. Additionally, some of the characters studied may represent independent evolution through convergence in some cases (e.g., horizontal axis of the neural column) and parallelism in others (e.g., present or absent from the transverse process).

An Investigation on the Seismic Behavior of the End-Plate Connection between a Steel Beam and the Weak-Axis of an H-Shaped Column Using a U-Shaped Connector

The seismic behavior of the end-plate connections between a steel beam and the weak axis of the H-shaped steel column using a U-shaped connector was investigated using numerical analysis. Finite element (FE) models were established using ABAQUS 6.14 software, and the applicability of the modeling approach was verified by comparing the numerical results with the relevant experimental results. This parametric study of the joint was carried out to analyze the effects of the thickness of the U-shaped connectors, the thickness of the end-plates, the axial compression ratio of the columns, and the linear stiffness ratio of the beam to the column. The results show that the U-shaped connector set in the weak axis of the H-shaped column can form a box-shaped panel zone with the column flange and web. The volume of the panel zone and its resistance to shear deformation are increased through this connection. Finally, the recommended reasonable ranges for the thickness of the U-shaped connector, the thickness of the end-plates, the axial compression ratio of the columns, and the linear stiffness ratio of the beam to the column are proposed in this paper.

Improving a Conventional Connection of Beam-to-Weak Axis of H-shaped Column to Modify Load Path in Panel Zone

This study aims to propose an improvement to the conventional connection of beam-to-weak axis of H-shaped columns with in-plane load paths and to compare the improved connection with the conventional one. The conventional connection detail consists of continuity plates and face plates, while the improved connection detail, in addition to the previous components, has a plate perpendicular to the column web (middle panel zone) acting as a panel zone. A numerical study using ABAQUS was conducted, and the study results showed that the most appropriate value for the middle panel zone thickness is equal to the column flange thickness, and it should be designed for 30% of the force demand induced by the beam bending moments. Furthermore, the study findings indicated that the proposed connection resulted in an average of 59.5% decrease in the force demands induced to the panel zone in comparison with the conventional connection. In addition, it was observed that the force demand on the face plate experienced the most decrease due to reducing the out-of-plane performance of the face plate in the improved connection models. Moreover, the results showed that the improved connection models experienced lower levels of von Mises stress, approximately 35.7% less than the conventional connection models.

Theory for nonlinear conductivity switching in semiconducting organic ferroelectrics.

In this work, the ferroelectric and semiconducting properties of the organic semiconducting ferroelectric benzotrithiophene tricarboxamide (BTTTA), and especially their nonlinear coupling, are theoretically investigated. BTTTA is an exponent of a small class of semiconducting organic ferroelectrics for which experiments have established a surprising polarization direction dependence of the bulk conductivity at finite fields. First, molecular dynamics (MD) simulations are used to investigate the occurrence and, under the influence of an external electric field, the inversion of the macroscopic electric dipole that forms along the axis of supramolecular columns of BTTTA. The MD results are consistent with the experimentally observed ferroelectric behavior of the material. Building on the MD results, a QM/MM scheme is used to investigate the charge carrier mobility in the quasi-1D BTTTA stacks in the linear and non-linear regimes. Indeed, at finite electric fields, a clear resistance switching effect was observed in the form of a hole mobility that is a factor ∼2 larger for antiparallel orientations of the polarization and field than for a parallel orientation. This phenomenon can be understood as a microscopic ratchet that is based on the non-equilibrium interaction between the (oriented) dipoles and the (direction of the) charge transport.

Analysis and Research on Load Behavior of H-shaped Steel Concrete

Steel-reinforced concrete (SRC) possesses excellent strength and numerous advantages over traditional concrete, making it extensively used in high-rise buildings and large-span bridge structures. This paper commences with the constitutive relationship of steel reinforcement in SRC, the nominal stress-strain conversion, and real stress-strain transformation. It employs Abaqus for nonlinear finite element analysis to study the stress variations in compressed SRC columns subjected to reciprocating loads and examines load-displacement curves. The paper analyzes the hysteresis loops of SRC columns under reciprocating loads, the trends in skeleton curves, energy dissipation, and stiffness degradation. Consequently, it concludes that the variation of compressive stress along the axis of SRC columns is consistent with the change in bearing capacity. Under reciprocating loads, the stress at the lower end of the SRC column is greater than that at the upper end, suggesting the need for reinforcement in the lower portion. The hysteresis loop of SRC columns exhibits a rich characteristic, with increasing energy absorption as displacement increases.

Guiding centre motion for particles in a ponderomotive magnetostatic end plug

The Hamiltonian dynamics of a single particle in a rotating plasma column, interacting with an magnetic multipole is perturbatively solved for up to second order, using the method of Lie transformations. First, the exact Hamiltonian is expressed in terms of canonical action-angle variables, and then an approximate integrable Hamiltonian is introduced, using another set of actions and angles, which describe the centre of oscillation for the particle. The perturbation introduces an effective ponderomotive potential, which to leading order is positive. At the second order, the pseudopotential consists of a sum of terms of the Miller form, and can have either sign. Additionally, at second order, the ponderomotive interaction introduces a modification to the particle effective mass, when considering the motion along the column axis. It is found that particles can be axially confined by the ponderomotive potentials, but acquire radial excursions which scale as the confining potential. The radial excursions of the particle along its trajectory are investigated, and a condition for the minimal rotation frequency for which the particle remains radially confined is derived. Last, we comment on the changes to the aforementioned solution to the pseudopotentials and particle trajectory in the case of resonant motion, that is, a motion which has the same periodicity as the perturbation.

Laminar organization of neocortical activities during systemic anoxia

The neocortex is highly susceptible to metabolic dysfunction. When exposed to global ischemia or anoxia, it suffers a slowly propagating wave of collective neuronal depolarization that ultimately impairs its structure and function. While the molecular signature of anoxic depolarization (AD) is well documented, little is known about the brain states that precede and follow AD onset. Here, by means of multisite extracellular local field potentials and intracellular recordings from identified pyramidal cells, we investigated the laminar expression of cortical activities induced by transient anoxia in rat primary somatosensory cortex. Soon after the interruption of brain oxygenation, we observed a well-organized sequence of stereotyped activity patterns across all cortical layers. This sequence included an initial period of beta-gamma activity, rapidly replaced by delta-theta oscillations followed by a decline in all spontaneous activites, marking the entry into a sustained period of electrical silence. Intracellular recordings revealed that cortical pyramidal neurons were depolarized and highly active during high-frequency activity, became inactive and devoid of synaptic potentials during the isoelectric state, and showed subthreshold composite synaptic depolarizations during the low-frequency period. Contrasting with the strong temporal coherence of pre-AD activities along the vertical axis of the cortical column, the onset of AD was not uniform across layers. AD initially occurred in layer 5 or 6 and then propagated bidirectionally in the upward and downward direction. Conversely, the post-anoxic waves that indicated the repolarization of cortical neurons upon brain reoxygenation did not exhibit a specific spatio-temporal profile. Pyramidal neurons from AD initiation site had a more depolarized resting potential and higher spontaneous firing rate compared to superficial cortical cells. We also found that the propagation pattern of AD was reliably reproduced by focal injection of an inhibitor of sodium‑potassium ATPases, suggesting that cortical AD dynamics could reflect layer-dependent variations in cellular metabolic regulations.

Size effect and lateral pressure effect on the mechanical resistance of columnar jointed basalt

To reveal the size effect and lateral pressure effect of columnar jointed basalts (CJBs), the meso-damage mechanics, statistical strength theory, continuum mechanics and digital image correlation are combined, and a series of heterogeneous numerical models of CJBs orthogonal and parallel to column axis are established. The elastic modulus, Poisson's ratio, uniaxial compressive strength, friction angle, residual strength coefficient, heterogeneity index of basalts 60 GPa, 0.2, 120 MPa, 56.15°, 0.1 and 5, respectively. The gradual fracture processes and acoustic emission characteristics of CJBs suffering various lateral pressures are numerically simulated under the axial loading rate of 0.05 mm/min, and the influence of model size on the anisotropy and lateral pressure effect of CJBs is analyzed. The results show that: for the direction I/Ⅱ orthogonal to column axis, when the lateral pressure is 2 MPa and 6 MPa, the critical value of size effect is 4 m and 6 m, respectively; for the direction parallel to column axis, the compressive strength of specimen can be obviously improved by increasing lateral pressure for the certain sizes; when the lateral pressure is 6 MPa and the distance ratio of the secondary joint set is 0% or 50%, the compression strengths of the 3 m and 6 m specimens change in a U-shape and a V-shape with the column dip angle increasing, respectively. The results can contribute to understanding the non-linear deformation and failure behaviors of CJBs.

High-frequency vortex dynamics and losses in the mixed state of nanostructured superconductors with columnar defects

We suggest a theoretical model for the microwave response of Abrikosov vortices in nanostructured superconductors with columnar defects, which serve as effective pinning sites for vortices that are considered elastic strings. For this case, we suppose that microwave losses related to the vortex oscillations in a microwave field arise caused by viscous oscillations of vortex kinks, which connect different parts of the vortex line pinned on adjacent columnar defects and vortex segments pinned on these defects. We consider the case of inclined magnetic field H, which creates vortex staircases consisting of pinned vortex segments and vortex kinks inside the superconductor. In this case, rf losses due to viscous kinks oscillations under the microwave current action arise even at T = 0 if the inclination angle of the magnetic field θΗ, concerning the columnar pinning site axis (z axis), exceeds some locking angle value θL.

Experimental analysis of the orientation distribution of cylindrical particles with different aspect ratios in random packed beds

This paper provides new experimental data on the orientation of cylindrical particles (defined as angle φ between the particle’s axis and the line parallel to the column axis) in random packed beds. In particular, the effect of particle’s aspect ratio is examined in detail. Three different values of particle’s aspect ratio in three columns with different diameters were examined. The research was also supplemented with numerical reconstructions of experimental cases in order to assess, among others, the capability of the numerical model to reproduce the orientation distribution for various aspect ratios. The effect of particles’ aspect ratio on particles’ orientation was found to be particularly evident in narrow columns where small values of φ become more favoured with increasing particles’ aspect ratio. In wider columns the effect is opposite as there is more significant contribution of higher angles. Also, the largest difference between loose and dense packing can be seen in narrow columns and is particularly manifested by a noticeable variation in probability of small orientation angles.

The Formation and Stationary Maintenance of Peaked Pressure Profiles in Turbulent Tokamak Plasmas

The theoretical model for increasing peaking of radial distribution of plasma thermal energy and plasma energy confinement time improvement due to the formation of current profiles those provide the increased value of the safety factor qb at the outer plasma boundary is considered. The model for the formation and stationary maintenance of the peaked current density profiles those ensure the maintenance of plasma column equilibrium state with increased qb value and conservation of q0=1 at the magnetic axis is developed. The model is based on the significant ramp down of the Iind current maintained by the inductor with simultaneous central ECR heating and electron cyclotron current drive (ECCD) switching on. It is shown by the computer simulations of the self-consistent time evolution of turbulent plasma for the conditions of T-10 and T-15MD tokamaks that in the shot scenarios with three- or four-fold decrease in the Iind current at the ECRH stage of shots it was achieved an approximately two-fold enhancement of the electron and ion temperatures at the axis of the plasma column as compared to the standard shots with the same heating powers.

The Formation and Stationary Maintenance of Peaked Pressure Profiles in Turbulent Tokamak Plasmas

The theoretical model for increasing peaking of radial distribution of plasma thermal energy and plasma energy confinement time improvement due to the formation of current profiles those provide the increased value of the safety factor {{q}_{b}} at the outer plasma boundary is considered. The model for the formation and stationary maintenance of the peaked current density profiles those ensure the maintenance of plasma column equilibrium state with increased {{q}_{b}} value and conservation of {{q}_{0}} approx 1 at the magnetic axis is developed. The model is based on the significant ramp down of the {{I}_{{{text{ind}}}}} current maintained by the inductor with simultaneous central ECR heating and electron cyclotron current drive (ECCD) switching on. It is shown by the computer simulations of the self-consistent time evolution of turbulent plasma for the conditions of T-10 and T-15MD tokamaks that in the shot scenarios with three- or four-fold decrease in the {{I}_{{{text{ind}}}}} current at the ECRH stage of shots it was achieved an approximately two-fold enhancement of the electron and ion temperatures at the axis of the plasma column as compared to the standard shots with the same heating powers.

Antegrade Posterior Column Acetabulum Fracture Screw Fixation via Posterior Approach: A Biomechanical Comparative Study.

Background and Objectives: Minimally invasive surgeries for acetabulum fracture fixation are gaining popularity due to their known advantages versus open reduction and internal fixation. Antegrade or retrograde screw fixation along the long axis of the posterior column of the acetabulum is increasingly applied in surgical practice. While there is sufficient justification in the literature for the application of the anterior approach, there is a deficit of reports related to the posterior approach. The aim of this study was to evaluate the biomechanical competence of posterior column acetabulum fracture fixation through antegrade screw placement using either a standard cannulated screw or a cannulated compression headless screw (CCHS) via posterior approach. Materials and Methods: Eight composite pelvises were used, and a posterior column acetabulum fracture according to the Letournel Classification was simulated on both their left and right sides via an osteotomy. The sixteen hemi-pelvic specimens were assigned to two groups (n = 8) for either posterior column standard screw (group PCSS) or posterior column CCHS (group PCCH) fixation. Biomechanical testing was performed by applying steadily increased cyclic load until failure. Interfragmentary movements were investigated by means of motion tracking. Results: Initial stiffness demonstrated significantly higher values in PCCH (163.1 ± 14.9 N/mm) versus PCSS (133.1 ± 27.5 N/mm), p = 0.024. Similarly, cycles and load at failure were significantly higher in PCCH (7176.7 ± 2057.0 and 917.7 ± 205.7 N) versus PCSS (3661.8 ± 1664.5 and 566.2 ± 166.5 N), p = 0.002. Conclusion: From a biomechanical perspective, CCHS fixation demonstrates superior stability and could be a valuable alternative option to the standard cannulated screw fixation of posterior column acetabulum fractures, thus increasing the confidence in postoperative full weight bearing for both the patient and treating surgeon. Whether uneventful immediate postoperative full weight bearing can be achieved with CCHS fixation should primarily be investigated in further human cadaveric studies with a larger sample size.

조직 분석(ASTM E1382)에 의한 용융흔 정량적 판별 연구

The molten marks of electrical wiring found at the fire site can be helpful in inferring the cause of the fire and the ignition point, and it is a very important piece of evidence. However, in the fire department, there are few cases of quantitative analysis and study on the texture of molten marks. In this study, based on the ASTM E1382 standard, using an analysis program called iSolution DT, the image taken with an electron microscope is analyzed and quantitatively determined. In a energized state, the electric wiring was short-circuited at 25°C and 600°C to form molten marks. The primary melt scar shorted at 25°C showed a small columnar structure major axis ratio (GAR), and the secondary melt scar shorted at 600°C showed a large major axis ratio (GAR). As a result, it will be very helpful in quantitatively classifying primary and secondary melt traces using isolution DT.