Full Unloading Research Articles

Research on Train Loading and Unloading Mode and Scheduling Optimization in Automated Container Terminals

In some automated container terminals, railway lines have been implemented into the port, saving container transfer time. However, the equipment scheduling level of the railway yard needs to be improved for managers. In the equipment scheduling of loading and unloading containers for railway trains, the operation modes “full unloading and full loading” and “synchronous loading and unloading” are often adopted. Due to the long length of the railway yard and the line of one train, there are two ways to arrange loading and unloading tasks for automated rail-mounted gantry cranes (ARMGs): one is to pre-assign tasks for ARMGs, and the other is to not pre-assign tasks for ARMGs. To investigate the efficacy of these different operation modes and methods of assigning tasks, this study formulated three mixed-integer linear programming (MILP) models with the goal of minimizing the ARMG task completion time. An adaptive large neighborhood search algorithm was used to tackle the scheduling problem. The scheduling effects of different operation modes and methods for assignment tasks were compared in terms of their calculation time and the completion time of ARMG tasks. Notably, the findings reveal that, with an increase in the number of tasks, the “pre-assign” task arrangement had a limited effect on the completion time of the ARMG tasks, made the calculation time shorter, and reduced the complexity of the problem. From the perspective of the completion time of ARMG tasks, the time under the “synchronous loading and unloading” operation mode was less than that of the “full unloading and full loading” operation mode. Therefore, it is recommended that the managers of the railway yard in an automated container terminal adopt the “synchronous loading and unloading” operation mode but determine the task assignment method according to decision time requirements. In addition, when the number of tasks is large, to decrease the time to complete ARMG tasks, the manager can adopt the “non-pre-assign” task distribution method.

Ballast Settlement Accumulation in Zones with Unsupported Sleepers

The high influence of impact and vibration on the behavior of crushed stone and ballast materials has been known for a long time. The zones with unsupported sleepers, which are always present in transition zones, crossings, welds, etc., are typically characterized by impact interaction, ballast full unloading, and additional preloading. However, no studies on ballast layer settlements consider impact vibration loading. Moreover, the influence of the cyclic loading on the ballast settlement intensity is considered ambiguously, with both decelerating and accelerating trends. The comprehensive literature review presents the influence of factors on settlement intensity. The present study aims to estimate the long-term processes of sleeper settlement accumulation depending on the loading factors: impact, cyclic loading, and preloading. The typical for a void zone ballast loading pattern was determined for various void sizes and the position along the track by using a model of vehicle-track interaction that was validated by experimental measurements. The loading patterns were parametrized with four parameters: maxima of the cyclic loading, impact loading, sleeper acceleration, and minimal preloading. A specially prepared DEM simulation model was used to estimate the ballast settlement intensity after initial settlement stabilization for more than 100 loading patterns of the void zone cases. The settlement simulation results clearly show that even a low-impact loading pattern causes many times increased settlement intensity than ordinary cyclic loading. Moreover, the initial preloading in the neighbor-to-void zones can cause even a decrease in the settlement intensity compared to the full ordinary or partial unloading. A statistical analysis using a machine learning approach and an analytic one was used to create the model for the intensity prediction regarding the loading patterns. The analytic approach demonstrates somewhat lower prediction quality, but it allows to receive plausible and simple analytic equations of the settlement intensity. The results show that the maximal cyclic loading has a nonlinear influence on the settlement intensity that corresponds to the 3–4 power function, and the impact loading is expressed by the linear to parabolic function. The ballast’s minimal preloading contributes to the reduction of the settlement intensity, especially for high cyclic loadings that are typical for neighbor-to-void zones. The results of the present study could be used for the complementing of the present phenomenological equations with the new factors and further application in the algorithms of the settlements accumulation prediction.

ANALYTICAL SOLUTION OF THE CREEP PROBLEM VISCOELASTIC MATERIAL IN A ROUND TUBE

Using a mathematical model of large deformations of materials with elastic, plastic and viscous properties, an analytical solution was obtained for deformation under creep conditions of a bung in a round tube with a varying pressure drop. The motion is considered taking into account the sliding of the material in the vicinity of the rigid wall of the pipe and its deformation under increasing, constant and decreasing pressure. Displacements, reversible and irreversible deformations, stresses at all stages of deformation, including residual deformations and stresses at full unloading are calculated.

Preferred orientation of calcium silicate hydrate and its implication to concrete creep

Calcium silicate hydrate (C–S–H) is the primary binding phase of cement-based and alkali-activated materials. The preferred orientation of C–S–H under non-hydrostatic pressure (e.g., uniaxial/biaxial load) is overlooked yet crucial in understanding concrete's multiscale mechanical performance. Here, we unveil the texture formation of C–S–H under compressive deviatoric stress, S, from 0 to ∼200 MPa, using high-pressure X-ray diffraction. Texture initiated at S < 12 MPa: the c-axis (normal to the basal plane) of C–S–H nanocrystallites preferentially re-oriented towards the direction of the principal compressive stress. Below S ∼100 MPa, the preferred orientation intensified through translation and rotation of C–S–H nanocrystallites; above ∼100 MPa, the texture stopped growing then weakened, suggesting internal transformations of C–S–H nanocrystallites. The time-dependence of the preferred orientation development is unveiled by the texture weakening after full unloading. The findings implicate that concrete creep under service loads is contributed by the intergranular preferential re-orientation of C–S–H nanocrystallites, not interlayer sliding or silicate chain breakage.

DETERMINATION OF TENSIONS OF SUSPENDED ROPES OF THE BRIDGE BY FREQUENCY OF NATURAL OSCILLATIONS

The article deals with the issues of development and use of equipment for digital measurements of rope tension based on the frequency of free transverse oscillations. accurate measurement of rope tension is of practical importance. The relevance of this task for the national economy of Ukraine lies in the need to develop a simple and reliable method and equipment for quick and convenient measurement by construction engineers and operating engineers of rope tension in the construction industry. The practical significance of the work lies in the need to timely bring the span structure of the Arch Bridge of the Podilsky bridge crossing over the Dnipro River in Kyiv to the design position after the installation of metal structures with the transfer of the weight of the bridge truss to four main supports and 64 suspension cables with full unloading of four mounting supports for further arrangement of the bridge deck and completion of construction works. The object of the research is the process of measuring the tension of suspension ropes from the own weight of the metal part of the bridge during bringing the truss of the Arch Bridge to the design position of the metal structural elements of the bridge. The subject of the study is the determination of the impact of the combined movement of the upper attachment points (threaded cylindrical couplings) of 64 suspended ropes on the redistribution of the frequencies of natural oscillations and tensions in their contours.

High-accuracy ultrasonic method for in-situ monitoring of oil film thickness in a thrust bearing

The ultrasonic method has been widely applied to measure the oil film thickness – a critical variable that reflects lubrication conditions. However, due to the thermal dependence of ultrasonic signals, significant deviations in film thickness measurements are introduced, hindering the in-situ application of the ultrasonic technique. To address this issue, a real-time temperature compensation method that can accurately obtain the frequency domain information of the reference signal is proposed. Specifically, the reflection from the substrate-coating interface compensates for the thermal effect on the phase increment and amplitude attenuation – this is noted as “self-calibration”. An extra experimental test with a substrate-coating-air structure is performed to calibrate the thermal effect on the coating-induced phase shift – this part is denoted as “pre-calibration”. The combination of “self-calibration” and “pre-calibration” enables the overall temperature compensation strategy. After the effectiveness validation with a temperature-controlled experiment, the proposed method is implemented in a thrust bearing in a heavy-duty hydropower generator with full running conditions, including loading and unloading, normal speed and shut-down. The largely ranged oil film thickness (3–330 μm) is ultrasonically measured and compared with the theoretical value, showing a higher measurement accuracy than the eddy current method.

Control of Dynamic Stall on Swept Finite Wings

A low-amplitude high-frequency flow control strategy for mitigation of transient tip stall is demonstrated for the case of a finite swept wing using high-fidelity wall-resolved large-eddy simulations. A wing of aspect ratio and NACA 0012 section is considered at freestream Mach number and chord Reynolds number . The wing undergoes an oscillatory pitching motion with reduced frequency and angle of attack between and 22 deg, resulting in deep dynamic tip stall for the uncontrolled case. Spanwise uniform low-amplitude pulsed forcing is imparted through a zero-net mass flow blowing/suction slot located on the wing lower surface near the leading edge using both moderate and high frequencies, and 50, respectively. The imposed small fluctuations are amplified through the natural receptivity of the laminar separation bubble (LSB) and, in the case of the highest frequency, completely inhibit its bursting along the wing, which precludes outboard flow separation and subsequent dynamic tip stall. The lower-frequency forcing cannot overcome eventual bursting of the LSB near the wingtip; however, the resulting separation is localized to the tip region unlike the full outboard unloading of the uncontrolled case. Conditioning of the leading-edge flow through targeted manipulation of the LSB and its inherent dynamics maintained or enhanced the effectively attached flow throughout the pitching cycle, resulting in significant reductions in the cycle-averaged drag and in the force and moment excursions.

A novel reaction wheel unloading method with stability analysis for solar sails utilizing liquid crystal devices

Reaction wheels are capable of constituting a high-performance attitude control system for solar sails. Unloading is significant for reaction wheels to maintain their controllability when approaching saturation. However, traditional magnetic unloading method would become unavailable for solar sails, because of the weak-magnetic environment far away from the Earth. In order to realize the unloading for solar sails with high effectiveness and low cost, a universal unloading method utilizing liquid crystal devices (LCDs) with oblique microstructures is proposed in this paper. First of all, a theoretical force model is derived for force analysis of LCDs. After that, the envelope and the switch table of the LCDs on a solar sail is clearly defined. On this basis, the control methods for both the LCDs and the reaction wheels during unloading are provided, to ensure the rotation speed of wheels be smoothly reduced to zero. Stability analysis for the control methods is demonstrated based on the Lyapunov Stability Theorem, which not only proves the attitude maintains stable during unloading, but also leads to a sufficient condition for full unloading capability. Additionally, numerical simulation of a regular-hexagon solar sail with reaction wheels and LCDs is taken as an example, showing the effectiveness of the unloading method.

Application of Hydraulic Control Make-up and Rreak-up Device in Improvement Design of Drilling rig

Tunnel drilling rig is widely used in coal mine gas drainage, hidden disaster detection and other construction. In view of the serious problem of thread wear when loading and unloading drill pipe thread of underground drilling rig in coal mine, a pure hydraulic control device is developed. By adjusting the corresponding angle parameters of the hydraulic control device, two actions of rotary feeding can be realized, and the thread can be loaded and unloaded automatically according to the thread pitch. The design of the device is completed, and the structure is applied to the improved design of ZDY750L and ZDY2-300LM drilling rigs. The matching control of feed and rotation of the two drilling rigs when loading and unloading the drill pipe is realized, which can reduce the wear of the drill pipe thread when the full hydraulic drilling rig is loading and unloading, and provides a new idea and solution for the implementation of the full hydraulic drilling rig automatic loading and unloading.

Mechanism of Sleeper–Ballast Dynamic Impact and Residual Settlements Accumulation in Zones with Unsupported Sleepers

Unsupported sleepers or void zones in ballasted tracks are one of the most recent and frequent track failures. The void failures have the property of intensive development that, without timely maintenance measures, can cause the appearance of cost-expensive local instabilities such as subgrade damages. The reason for the intensive void development lies in the mechanics of the sleeper and ballast bed interaction. The particularity of the interaction is a dynamic impact that occurs due to void closure. Additionally, void zones cause inhomogeneous ballast pressure distribution between the void zone and fully supported neighbour zones. The present paper is devoted to studying the mechanism of the sleeper–ballast dynamic impact in the void zone. The results of experimental in situ measurements of rail deflections showed the significant impact accelerations in the zone even for lightweight slow vehicles. A simple three-beam numerical model of track and rolling stock interaction has shown dynamic interaction similar to the experimental measurements. Moreover, the model shows that the sleeper accelerations are more than 3 times higher than the corresponding wheel accelerations and the impact point appears before the wheel enters the impact point. The analysis of ballast loadings shows the specific impact behaviour in combination with the quasistatic part that is different for void and neighbour zones, which are characterised by high ballast pre-stressed conditions. The analysis of void size influence demonstrates that the maximal impact loadings and maximal wheel and sleeper accelerations appear at a certain void depth, after which the values decrease. The ballast quasistatic loading analysis indicates an increase of more than 2 times in the ballast loading in neighbour zones for long voids and almost full quasistatic unloading for short-length voids. However, the used imitation model cannot explain the nature of the dynamic impact. The mechanism of the void impact is clearly explained by the analytic solution using a simple clamped beam. A simplified analytical expression of the void impact velocity shows that it is linearly related to the wheel speed and loading. The comparison to the numerically simulated impact velocities shows a good agreement and the existence of the void depth with the maximal impact. An estimation of the long-term influences for the cases of normal sleeper loading, high ballast pre-stress and quasistatic loading in the neighbour zones and high impact inside the void is performed.

Modified ant colony optimization algorithm for solving the vehicle routing problem with a given load capacity

The article presents a mathematical model of the Vehicle routing problem with loading constraints in the form of a mathematical programming problem. A modification of the Ant colony optimization algorithm is presented to solve the problem. The main idea of the modification is to use the probabilistic rule of returning the agent (ant) to the depot before full unloading. The source of such behavior of the agent can be the concept of «fullness» of the ant. The computational experiment for comparing the classical and modified Ant colony optimization algorithms is presented. Testing was carried out according to two schemes: intensive testing and cross-testing. The conclusions about the efficiency of the proposed algorithm are presented.

Nanomechanical characterisation of single‐crystal Bi 2 Se 3 topological insulator

Topological insulators (TIs) are recently discovered high-tech materials where their potential use in nanoelectronic devices such as spintronics and quantum computers, due to their unique electronic features, can be a solution to the emerging need for high-bit data processing. Yet their mechanical properties are not well understood for their use in practical applications. With the objective of exploiting the nanomechanical behaviour of TIs, bulk single-crystal Bi2Se3 TI is grown by using the Bridgeman–Stockbarger method and mechanically characterised by the nanoindentation method. The Young's modulus and hardness were extracted from the load-displacement data by using Oliver and Pharr's standard method. Further, fracture toughness of the material was reported for the first time after comprehensive research of indentation crack length (ICL) methods. The grown Bi2Se3 exhibits hardness and Young's modulus as 323 MPa and 6.018 GPa at nanoscale, respectively. Fracture toughness of the TI was evaluated at 0.034 MPa m1/2 and elastic recovery was around 60% after the full unloading process.

Discussions on the Complete Strain Energy Characteristics of Deep Granite and Assessment of Rockburst Tendency

In deep mining, the rockburst hazard has become a prominent problem. Rockburst is difficult to be predicted, and it gives a severe threat to mining safety. In this paper, the triaxial compressive tests with an acoustic emission (AE) device and full cyclic loading and unloading tests were carried out, respectively, to present characteristics of linear elastic strain energy and peak strain energy. Also, to consider the time-delay strain characteristics of granite found in the abovementioned tests, a new stage loading and unloading test with dual monitoring systems was designed and performed. Through 20 days’ time-delay strain monitoring, the peak-strength strain energy was further modified. The results showed that the peak strain energy is approximate 1.2-1.3 times than linear elastic strain energy under the same confining pressure, and after considering the time-delay strain effect, the modified maximal strain energy value of the deep granite significantly increased. The peak strain energy values are further enhanced from 1.0 × 104 J/m3 to 1.8 × 104 J/m3, respectively. At last, by taking advantage of the strain energy index model of rockburst, the tendency and intensity of rockburst were assessed contrastively.

Response to mechanical loading in rat Achilles tendon healing is influenced by the microbiome

We have previously shown that changes in the microbiome influence how the healing tendon responds to different treatments. The aim of this study was to investigate if changes in the microbiome influence the response to mechanical loading during tendon healing. 90 Sprague-Dawley rats were used. Specific Opportunist and Pathogen Free (SOPF) rats were co-housed with Specific Pathogen Free (SPF) rats, carrying Staphylococcus aureus and other opportunistic microbes. After 6 weeks of co-housing, the SOPF rats were contaminated which was confirmed by Staphylococcus aureus growth. Clean SOPF rats were used as controls. The rats were randomized to full loading or partial unloading by Botox injections in their calf muscles followed by complete Achilles tendon transection. Eight days later, the healing tendons were tested mechanically. The results were analysed by a 2-way ANOVA with interaction between loading and contamination on peak force as the primary outcome and there was an interaction for both peak force (p = 0.049) and stiffness (p = 0.033). Furthermore, partial unloading had a profound effect on most outcome variables. In conclusion, the response to mechanical loading during tendon healing is influenced by changes in the microbiome. Studies aiming for clinical relevance should therefore consider the microbiome of laboratory animals.

АНАЛИЗ ЯДЕРНОЙ БЕЗОПАСНОСТИ ПРИ ОБРАЩЕНИИ С ОТРАБОТАВШИМ ТОПЛИВОМ РЕАКТОРА МИР

The main results of neutron and physical parameters calculations, which are important for nuclear safety during storage and transportation of irradiated working and loop fuel assemblies and irradiation devices of the MIR reactor, as well as working in radiation-protective research cameras for the assembling and disassembling of irradiation devices, are introduced in this report. The analysis was made in full accordance with requirements of the state normative research nuclear facilities nuclear safety documents. The results of effective neutron reproduction coefficient calculations received by the MCU-RFFI/A program were used for the analysis. The various emergency situations associated with personnel errors, falling of products during their transportation, pouring out the contents of covers, violation of the products placement order, changing in inhibitor (in particular water) density were considered during the analysis. The full unloading of the reactor core in case of an accident was also considered. As a result of the neutron and physical calculations analysis, safety of spent nuclear fuel storage, at all stages of its transportation, as well as working in radiation- protective research cameras subject to established restrictions was proved. Restrictions for the number of products and the geometry of their placement in the cooling pool, transport corridor, and radiation - protective cameras were set.

Experimental investigation on the reversibility of concrete creep under repeating loads

So far, creep reversibility of concrete has been tested either under single unloading or stepwise (“staircase”) stress histories. However, these investigations do not provide a complete understanding of the creep behavior under repeating stress histories, similar to variable live load histories in usual concrete structures. Typical examples are parking garages, bridges or storage buildings with frequent but still longer-term loadings and unloadings. Therefore, the paper attempts to extend the knowledge on the creep under frequently repeated stresses by testing concrete specimens under various loading and drying conditions. The creep-recovery versus creep ratio over time, considered here as a measure of creep reversibility, was studied within two separate experiments. The first experiment aims to assess the influence of different service stress levels with 30% and 45% of the concrete compressive strength fc as well as different unloading levels of full and partial unloading. The second one focuses on the influence of different hygral conditions of the specimens, namely sealed and unsealed conditions. Regardless of the stress level, the creep-recovery versus creep ratio tends to approach unity after a sufficient number of loading and unloading cycles. Drying conditions show negligible effects on the creep recovery. On the other hand, they have remarkable influence on the proportion of the creep reversible in each loading cycle. Moreover, the basic creep component shows high reversibility under repeating stress histories. The results demonstrate that the recovery behavior under repeating stresses pronouncedly differs from the ones under just sustained stresses.

Percutaneous pulmonary artery venting via jugular vein while on peripheral extracorporeal membrane oxygenation running: a less invasive approach to provide full biventricular unloading

Percutaneous pulmonary artery venting via jugular vein while on peripheral extracorporeal membrane oxygenation running: a less invasive approach to provide full biventricular unloading

Preoperative and intraoperative extracorporeal membrane oxygenation adoption for long-term left ventricular assist device implantationive approach to provide full biventricular unloading

Preoperative and intraoperative extracorporeal membrane oxygenation adoption for long-term left ventricular assist device implantationive approach to provide full biventricular unloading

Observation and modeling of loading–unloading hysteresis behavior of unidirectional composites in compression

The loading–unloading hysteresis behavior of unidirectional HTS40/PA6 carbon/polyamide laminates under off-axis compression has been examined both experimentally and constitutively in the present study. Monotonic compressive tests are first performed on unidirectional laminates to identify the basic properties of off-axis deformation. Then, five cycles of compressive loading and unloading tests are carried out with a gradually increasing peak stress for each specimen, followed by testing to failure. Significant nonlinear unloading behavior is observed after the material has been loaded into the nonlinear deformation region, and apparent plastic strain is seen after full unloading. The reloading curve also exhibits nonlinearity and conduces to a slightly open hysteresis loop with unloading. An approach is developed to predict the nonlinear hysteresis behavior of unidirectional composites by assuming an anelastic strain component in the nonlinear compressive deformation. The assumption of anelastic strain is a modification of Sun–Chen’s one-parameter plasticity model that considers the nonlinear deformation completely as plastic strain from monotonic tests. The modified model has been validated by the off-axis loading–unloading test results on unidirectional laminates. Results verify that the model accurately captures not only the plastic strain but also the complex nonlinear hysteresis behavior in the observed off-axis loading–unloading stress–strain curves.

Partial or Complete Unloading of Skeletal Muscle Leads to Specific Alterations of Anabolic Signal Transduction

Consequences of disuse atrophy of skeletal muscle observed during spaceflight on astronaut health and performance are a focal point of space research. Decrements of both muscle mass and protein synthesis rates have been observed with exposure to varying muscle loading environments (1G > partial loading > 0G), and most of the reduced muscle mass can be attributed to diminished rates of synthesis. However, specific mechanisms behind unloading-dependent reductions of protein synthesis are not well defined. PURPOSE: To determine whether or not alterations of anabolic signal transduction was responsible for the changes previously observed in fractional synthesis rates with specific gravitational loading paradigms. METHODS: Female BALB/cByJ were normalized by bodyweight and assigned to normal cage ambulation (1G), partial weight bearing suspension titrated to approximately 33% bodyweight (G/3), partial weight bearing titrated to 16% bodyweight (G/6) and full unloading of hind limbs (0G) in specially designed cages. All mice were subjected to that loading environment for 21d prior to tissue harvest, and monitored daily. Immunoblotting of the gastrocnemius (n=23) was carried out to analyze alterations of anabolic signal transduction. Although numerous signaling intermediates were assessed, the focus of this abstract will be on ribosomal protein S6 kinase (p70-S6K). This important protein has served as a marker of protein synthesis signal transduction as well as the anabolic capacity in skeletal muscle. RESULTS: Regardless of loading paradigm, no differences were detected among groups for the activation of p70-S6K (as indicated by the phospho: total protein content). Total protein content, however, was ~27% lower than control in 0G and G/6 (P=0.008) with G/3 not being different from control (P>0.05). CONCLUSION: In combination with previous data (unpublished observations), ambulation at G/3 is sufficient to maintain anabolic signaling capacity when compared to G/6 or 0G, suggesting that a threshold level of stimulus is necessary to maintain anabolic capacity in muscle. These results may have important implications towards the development of strategies designed to counter the effects of partial/complete unloading on skeletal muscle based on how the anabolic capacity of muscle is affected.