Sinking Depth Research Articles

Human walking biomechanics on sand substrates of varying foot sinking depth.

Our current understanding of human gait is mostly based on studies using hard, level surfaces in a laboratory environment. However, humans navigate a wide range of different substrates every day, which incur varied demands on stability and efficiency. Several studies have shown that when walking on natural compliant substrates there is an increase in energy expenditure. However, these studies report variable changes to other aspects of gait such as muscle activity. Discrepancies between studies exist even within substrate types (e.g. sand), which suggests that relatively 'fine-scale' differences in substrate properties exert quantifiable influences on gait mechanics. In this study, we compare human walking mechanics on a range of sand substrates that vary in overall foot sinking depth. We demonstrate that variation in the overall sinking depth in sand is associated with statistically significant changes in joint angles and spatiotemporal variables in human walking but exerts relatively little influence on pendular energy recovery and muscle activations. Significant correlated changes between gait metrics are frequently recovered, suggesting a degree of coupled or mechanistic interaction in their variation within and across substrates. However, only walking speed (and its associated spatiotemporal variables) correlate frequently with absolute foot sinkage depth within individual sand substrates, but not across them. This suggests a causative relationship between walking speed and foot sinkage depth within individual sand substates is not coupled with systematic changes in joint kinematics and muscle activity in the same way as is observed across sand substrates.

Model Tests on Jacked Pile Penetration Characteristics Considering a Static Press-in Piling Machine

This study incorporates a static press-in piling machine into the conventional laboratory model tests for jacked piles. By conducting a comparative analysis between two tests, one involving the static press-in piling machine and the other focusing solely on pile jacking, this study aims to unveil the variations in penetration characteristics with pile sinking depth during the process of pile jacking under the constraint imposed by the static press-in piling machine. When considering the impact of the piling machine, the pile pressing force, pile sinking resistance, pile axial force, and unit side friction resistance of the pile body are higher compared to test results that only focus on pile jacking. There is an acceleration in the total side friction resistance within the depth range of 20 to 30 cm. Additionally, the reduction rate of axial force during the entire pile jacking process is 2% higher, with a general reduction in the “side resistance degradation” phenomenon. The soil pressure around the pile exhibits an initial increase followed by a decrease. The authors believe that the model box test of the jacked pile, considering the pile machine, would be more aligned with engineering practice.

Sinking Behavior of Netting Panels Made with Various Twine Materials, Solidity Ratios, Knot Types, and Leadline Weights in Flume Tank

Netting is an important component of fishing gear design, and its ability to sink determines the effectiveness of fishing gears such as purse seines, falling nets, and stick-held nets. Therefore, it is crucial to thoroughly investigate the sinking parameters (sinking depth and sinking speed) of the netting panel as a function of the leadline weights using various twine materials, knot types, and solidity ratios. In this study, a generalized additive model (GAM) was utilized to analyze the impact of each factor on the sinking performances of the netting. The results revealed that the sinking depth of the netting was positively correlated with sinking time and leadline weight. However, the netting featured a maximum sinking depth limit, indicating that the sinking depth would not increase beyond a leadline weight of 69.5 g. During the initial phase of the sinking process, the sinking velocity of each netting panel initially increased but gradually decreased over time. The incorporation of a leadline weight reduced sinking time. Thereby, polyester netting exhibited the shortest average sinking time. A comparison of netting types with similar solidity ratios showed that the maximum sinking depth of the nylon netting was 13.20% and 10.11% greater than that of polyethylene and polyester nettings, respectively. In addition, nylon nets’ time average sinking speed was 64.58% and 4.62% greater than that of polyethylene and polyester nettings, respectively. The analysis of the GAM model clearly showed that the leadline weight has a significant effect on the netting sinking speed and depth. To ensure that the netting can reach its maximum sinking speed, it is strongly recommended to use nylon and polyester nettings with a low solidity ratio, i.e., a lower twine diameter and greater mesh size with a higher leadline weight, when constructing fishing gear such as purse seines with higher net leadline weights.

Enhanced static simulation process of caisson sinking using the coupled Euler-Lagrange method

Caisson sinking is a vital process in marine engineering, and accurate simulations are crucial for predicting and preventing potential accidents or failures. Current numerical simulations necessitate measured engineering parameters, constraining their applicability. This study utilized the coupled Euler-Lagrange (CEL) method to compute specific parameters. These parameters served as substitutes for the engineering measurement values to enhance the static simulation process for the incremental height sinking of caissons, thereby addressing the constraints set by engineering measurements. The CEL method was initially utilized to simulate a dynamic permeation process, generating a series of valuable parameters such as the degree of caisson sinking and mud surface depth at the cavity bottom. Using these parameters instead of engineering measured parameters, a stable state model for incremental height sinking of caissons was established, followed by a static analysis. The improved method was subsequently applied to simulate the construction process involving caisson sinking, demonstrating its feasibility. This enhanced static simulation provides a novel approach for examining the equilibrium state of caisson subsidence, eliminating the need to wait for the actual construction phase to be completed. The proposed method exhibits the critical advantage of favorable predictability, allowing for the anticipation of potential mishaps, such as abrupt subsidence, and supplying timely cautionary information to facilitate proactive measures, ultimately reducing the incidence of engineering accidents or failures.

Hydrodynamic investigation on the submerged tunnel suspended from a fixed platform using SPH method

In this paper, the coupled dynamic motion characteristics of a tunnel element suspended from a platform have been studied at a 1:50 scaled model by using the weakly compressible Smoothed Particle Hydrodynamic (WCSPH) method. The corresponding numerical model was validated with the experimental published data of the motion characteristics of the tunnel suspended from a fixed platform, and the case of a floating structure with its mooring lines. Multiple linear wave conditions and different sinking depths of the submerged were involved in the numerical model for tunnel dynamic response and cable behavior investigation. Effects of the mooring system, the wave parameters, the tunnel sinking depth and its mooring configurations were studied. The numerical results were arranged to inform about the dynamic characteristics and mooring behavior for different case studies. The results indicate that the tunnel motions decrease with the increment of the tunnel sinking depth and decrease with the decreasing mooring angle. The natural periods of the tunnel-platform system play key roles in the wave condition impacts on the tunnel motions. It was found that the additional mooring system anchoring the tunnel to seabed played a specific role in reducing the tunnel motions in roll and sway, the motion amplitude of the tunnel in heave is mainly controlled by the suspension cables, particularly when subjected to lower sinking depth and longer period waves.

Change in the pituitary stalk deviation angle after transsphenoidal surgery can predict the development of diabetes insipidus for pituitary adenomas

We aimed to assess the factors influencing the development of diabetes insipidus after transsphenoidal surgery for pituitary adenomas. A retrospective analysis was conducted on the clinical data of patients with pituitary adenomas who underwent transsphenoidal surgery. The predictors of postoperative diabetes insipidus were determined using statistical analysis. Of the 415 patients who underwent microscopic transsphenoidal surgery for pituitary adenomas, 196 experienced postoperative diabetes insipidus. The sinking depth of the diaphragma sellae and the difference between the preoperative and postoperative pituitary stalk deviation angles in the diabetes insipidus group were greater than those in the non-diabetes insipidus group. Logistic regression analysis showed that the risk of diabetes insipidus after transsphenoidal surgery was higher in patients with a larger difference in their pituitary stalk deviation angles (odds ratio = 2.407, 95% CI = 1.335-4.342; P = 0.004). The difference in the pituitary stalk deviation angle could predict the onset of diabetes insipidus after transsphenoidal surgery for pituitary adenomas.

Numerical and experimental investigation on hydrodynamic performance of the stick-held dip net in Pacific saury fishery

Stick-held dip (SHD) net is an effective fishing gear target for catching the Pacific saury. In this study, the hydrodynamic performance of an SHD net in current was investigated by means of numerical simulation and experimental test, and a mathematical model based on the lumped-mass method and principle of rigid body kinematics was developed to predict the net shape and tension of the cable. A series of physical model tests based on Tauti’s law and full-scale measurements at sea were conducted to evaluate the applicability of the numerical model. The results showed that the prediction performance of the numerical model was good, with a mean relative error of approximately 20% among the numerical, experimental, and field measured data. The dynamic shooting behavior of the SHD net at different current velocities and the effects of the length of the hauling rope and the mesh size on the net shape and tension of the cable were analyzed using the numerical simulation approach. When the current velocity increased from 0.12 to 0.46 m/s, the enclosed volume of the SHD net decreased by 62.9%. The height of net opening increased by 9.29% to 13.53% for every 10% increase in the length of the hauling rope from 0.96 to 1.44 m. With the increase in mesh size from 24 to 30 and 35 mm, the sinking depth and speed of the net increased, and the tension force of the cables decreased by 9.02% and 12.10%, respectively. The results suggested that (1) the numerical model could realistically represent the hydrodynamic characteristics of the SHD net; (2) the suitable operation current velocity is below 0.60 m/s; (3) the reasonable length of the hauling rope is about 30 m; and (4) the mesh size of the main netting could be increased to 30 mm.

Novel Nomograms to Predict Delayed Hyponatremia After Transsphenoidal Surgery for Pituitary Adenoma.

ObjectiveThis study aimed to develop a nomogram of clinical variables and magnetic resonance imaging scans to predict delayed hyponatremia after transsphenoidal surgery for pituitary adenoma.MethodsPatients who underwent transsphenoidal surgery for pituitary adenoma in Fuzong Clinical Medical College of Fujian Medical University between January 2012 and December 2020 were retrospectively investigated. Medical records, MRI findings, and laboratory examination results were recorded as candidate variable predictors of delayed hyponatremia. A nomogram to predict delayed hyponatremia was formulated based on the multivariable model of risk factors. The predictive accuracy and discriminative ability of the nomogram were assessed using the receiver operating characteristic (ROC) curve, calibration plot, and decision curve analyses. The model underwent prospective validation in three medical centers with patients who underwent transsphenoidal surgery for pituitary adenoma between January 2021 and February 2022.ResultsThe model that incorporated the postoperative length of “measurable pituitary stalk,” pituitary stalk deviation angle difference, postoperative diabetes insipidus, sinking depth of diaphragma sellae, and blood sodium level on the second postoperative day was developed and presented as the nomogram of the training cohort. The nomogram achieved area under the ROC curve (AUCs) of 0.806 and 0.849 for the training cohort and the testing cohort, respectively, and displayed good calibration. Decision curve analysis showed that the nomogram was clinically useful when the threshold probability was 13–96%.ConclusionsWe developed a nomogram to evaluate the individualized prediction of delayed hyponatremia after transsphenoidal surgery for pituitary adenomas.

Are Sunken Warships Biodiversity Havens for Corals?

Coral reefs are threatened by climate change, overfishing, and pollution. Artificial reefs may provide havens for corals, both to escape warming surface waters and to assist in the geographic migration of corals to more habitable natural reef conditions of the future. The largest artificial reefs have been generated by nearly 2000 shipwrecks around the world, but the coral diversity on these wrecks is virtually unknown. Ship size and hull material, location relative to natural reef, time since sinking, ocean currents, and water depth may affect coral diversity. As a test of the biodiversity capacity of very large sunken structures relative to surrounding natural reef, we carried out technical diver-based surveys to quantify genus-level coral diversity on 29 warships sunk in Bikini Atoll and Chuuk Lagoon. We also assessed whether ship length, as an index of substrate availability, and water depth, as an indicator of light and temperature, can serve as predictors of coral diversity. We surveyed a total of 9105 scleractinian corals. The total number of genera identified at Bikini was 34, and at Chuuk it was 51, representing 67% and 72% of genera found on natural reefs at Bikini and Chuuk, respectively. Ship length, but not water depth, was positively correlated with relative abundance and richness at the genus level. Our results suggest that very large wrecks can serve as havens for reef-building corals with a broad genetic diversity, expressed at the genus level, commensurate with corals found on neighboring natural reefs. The role of large artificial reefs could include protecting coral biodiversity from warming surface waters.

Analiza sila zatezanja pređe u fazi kuliranja kod kružno pletaćih mašina

In the process of loop formation, the weft knitting phase has a dominant place, both from the aspect of forming the loop as well as determination its length and geometric shape. The loop length is the most important technological parameter in the knitted fabrics structure analysis and it is directly a function of sinking depth. The yarn tension in the weft knitting phase is determined by the following parameters: values of yarn tension at the entrance to the knitting system, yarn friction with knitting needles, yarn guiding speed, yarn bending stiffness and yarn angle coverage with knitting needles. Determination the value of yarn tension in the weft knitting phase is extremely important for the reliability of the knitting process. The obtained results show that the maximum values of yarn tension in the loop formation process occur in the weft knitting phase and that they must not be greater than the forces of the elastic limit of the used yarn.

Diaphragma sellae sinking can predict the onset of hyponatremia after transsphenoidal surgery for pituitary adenomas.

Sinking of the diaphragma sellae (DS) may stretch the pituitary stalk, which in turn impairs neurohypophyseal function; thus, it may play a role in the development of postoperative hyponatremia. We aimed to assess the factors influencing the development of hyponatremia after transsphenoidal surgery (TSS) for pituitary adenomas and analyze the effect of DS sinking on hyponatremia. After applying the inclusion and exclusion criteria, we retrospectively analyzed the clinical data of patients with pituitary adenoma who underwent TSS. The pituitary gland was scanned using a 3.0-T magnetic resonance imaging, and sagittal and coronal images were acquired. We evaluated the following: preoperative and postoperative hypothalamus‒pituitary‒thyroid axis function, hypothalamus‒pituitary‒adrenal axis function, intra-operative cerebrospinal fluid leaks, diabetes insipidus, hyponatremia, time from the day of surgery to the day of discharge, and time of hyponatremia onset. Of the 460 patients who had microscopic TSS for pituitary adenoma, 83 experienced postoperative hyponatremia. Hyponatremia occurred approximately 5.25days postoperatively and persisted for 5.54days. The lowest average blood sodium level was 123.9mEq/L, which occurred at 7.49days after surgery. Logistic regression analysis showed that the risk of hyponatremia was greater for patients with a significant DS sinking depth, a large pituitary stalk deviation angle difference, and a longer postoperative "measurable pituitary stalk". The difference in blood sodium levels between pre-TSS and 2days post-TSS was also an independent predictor of postoperative hyponatremia onset. DS sinking plays an important role in predicting hyponatremia onset after TSS for pituitary adenomas.

Simulation Analysis and Experimental Study on the Working State of Sinking Headframe in the Large Underground Shaft

Based on the newly developed sinking headframe for the deep and large shaft, the finite element model of the full-scale headframe was established by using SAP2000. Through the calculation, the theoretical stress of the headframe at sinking depths of 40 m, 143 m, 223 m, 518 m, 762 m, 1000 m, 1250 m, and 1503 m was obtained and then compared with the field measured stress. The results show that with the increase of shaft sinking depth, the theoretical stress of finite element simulation and the field measured stress of each member of the sheave wheel platform and the headframe increase linearly, and for the maximum member stress in the upper, middle, and lower layers of the headframe, the numerical simulation value is greater than the field measured value and less than the designed steel strength. In other words, under normal working conditions, headframe members are in the elastic stress stage and meet the design requirements, and instability failure of headframe members will not occur. The end-restraint mode of the supporting bars has a great influence on the force of the top member. The reasonable selection of the restraint mode in the simulation is the key to the accuracy of the calculation results. The simulation results well reflect the actual stress of the headframe and provide a reliable guarantee for the follow-up work of the project.

Mechanical and acoustic absorption characteristics of UHMWPE weft-knitted structures of flexible porous laminated composites

The study investigated the mechanical and acoustic absorption characteristics of ultrahigh molecular weight polyethylene (UHMWPE) weft-knitted structures of flexible porous laminated composites. Weft-knitted structure reinforcements were fabricated using UHMWPE filaments, with various yarn fineness, sinking depths, and laminating layers. The acoustic absorption performance of UHMWPE weft-knitted structures of flexible porous laminated composites was evaluated using a standing wave tube system. The results revealed that the acoustic absorption capacity of composites can be enhanced by increasing the thickness of the composites. The acoustic absorption coefficient of RL 400 D three-layered composites was 50% higher than that of the double-layered composites. The response surface methodology analyses results revealed that optimum acoustic absorption at low frequency was attained by the composites at a yarn fineness of 400 D, a sinking depth of 10.5 mm, and double-layered structures. However, response surface analysis at a frequency of 2000 Hz was not significant.

Global Modeled Sinking Characteristics of Biofouled Microplastic.

Microplastic debris ending up at the sea surface has become a known major environmental issue. However, how microplastic particles move and when they sink in the ocean remains largely unknown. Here, we model microplastic subject to biofouling (algal growth on a substrate) to estimate sinking timescales and the time to reach the depth where particles stop sinking. We combine NEMO‐MEDUSA 2.0 output, that represents hydrodynamic and biological properties of seawater, with a particle‐tracking framework. Different sizes and densities of particles (for different types of plastic) are simulated, showing that the global distribution of sinking timescales is largely size‐dependent as opposed to density‐dependent. The smallest particles we simulate (0.1 μm) start sinking almost immediately around the globe and their trajectories take the longest time to reach their first sinking depth (relative to larger particles). In oligotrophic subtropical gyres with low algal concentrations, particles between 1 and 0.01 mm do not sink within the simulation time of 90 days. This suggests that in addition to the comparatively well‐known physical processes, biological processes might also contribute to the accumulation of floating plastic (of 1–0.01 mm) in subtropical gyres. Particles of 1 μm in the gyres start sinking largely due to vertical advection, whereas in the equatorial Pacific they are more dependent on biofouling. The qualitative impacts of seasonality on sinking timescales are small, however, localized sooner sinking due to spring algal blooms is seen. This study maps processes that affect the sinking of virtual microplastic globally, which could ultimately impact the ocean plastic budget.

Numerical study on the dynamic characteristics of water entry of cavity body using two-phase SPH method

The air usually has a major influence on the water entry of a typical cavity body (cavity body is a hollow, cylindrical, semi-closed structure), which not only lowers the slamming load but also affects the dynamic characteristics of water entry. In this paper, a two-phase smoothed particle hydrodynamics (SPH) model for simulating the water entry of cavity body is presented. The SPH model combined with Riemann solver is improved to deal with the two-phase flows with the discontinuous quantities across the interface. One-sided Riemann problem is used to impose the fluid–structure interaction and a switch-function-based Riemann solver dissipation is formulated to improve the interfacial instability owing to the strong impact. The motion equations of rigid body are incorporated into two-phase SPH model to describe the motion of cavity body. The proposed model is validated by research on the test cases in the published literature. Finally, this work presents a study of water entry of cavity body by experiment and this two-phase SPH method. The dynamics phenomena in the coupling process between cavity body and two-phase flow are investigated. And the effects of air, mass, the sizes and incline angles of cavity body on the dynamic characteristics of cavity body and two-phase flows are shown. An improved two-phase SPH model was used to simulate the water entry of cavity body. The cavity body impacts the water surface and the cavity body is closed by the flooding water. It comes into being open air cavity and water jets. The jet walls protrude and the air cavity is closed. With the increase of the water entry depth, the complex hydrodynamic phenomena can be seen again. The sinking depth shows the law of fluctuation up and down with time.

Influence Analysis of Large-area PHC Pipe Pile Construction on the Surrounding Environment in Deep Silt Site

There are a large number of deep and thick soft soil foundations along the river and coastal areas. PHC pipe piles have become one of the foundation treatment methods widely used in soft soil foundations. Taking the construction of a pile foundation project in Wenzhou as an example, the thickness of the dredger fill and silt at the site is 27.20∼33.60m, and the impact of large-area pile group construction on the surrounding environment is discussed. The results show that: (1) The load imposed on the pile top and the pile sinking depth during the construction of the foundation pile increase according to an exponential function. (2) The direction of horizontal soil squeezing deformation around the field is related to the position of the measuring point. The corner range is small and the middle range is larger, but the direction of maximum displacement is basically along the shortest line between the pile position and the measuring point. (3) The vertical direction of the measuring point varies greatly with the construction time and pile position, and the uplift and settlement appear repeatedly. The monitoring results can provide a reference for the construction of similar projects.

It's in the loop: shared sub-surface foot kinematics in birds and other dinosaurs shed light on a new dimension of fossil track diversity.

The feet of ground-dwelling birds retain many features of their dinosaurian ancestry. Experiments with living species offer insights into the complex interplay among anatomy, kinematics and substrate during the formation of Mesozoic footprints. However, a key aspect of the track-making process, sub-surface foot movement, is hindered by substrate opacity. Here, we use biplanar X-rays to image guineafowl walking through radiolucent substrates of different consistency (solid, dry granular, firm to semi-liquid muds). Despite substantial kinematic variation, the foot consistently moves in a looping pattern below ground. As the foot sinks and then withdraws, the claws of the three main toes create entry and exit paths in different locations. Sampling these paths at incremental horizons captures two-dimensional features just as fossil tracks do, allowing depth-based zones to be characterized by the presence and relative position of digit impressions. Examination of deep, penetrative tracks from the Early Jurassic confirms that bipeds had an equivalent looping response to soft substrates approximately 200 Ma. Our integration of extant and extinct evidence demonstrates the influence of substrate properties on sinking depth and sub-surface foot motion, both of which are significant sources of track variation in the fossil record of dinosaurs.

Model development and performance investigation of staggered tube-bundle heat exchanger for seawater source heat pump

Seawater heat pump system exhibits merits of reducing building energy consumption, while enhancing the heat transfer of seawater heat exchangers is the key to improve the system performance. The effect of seawater flow behavior on the thermal performance of seawater heat exchanger immersed in oscillating flow is significant but often neglected. An unsteady mathematical model was firstly developed to describe heat transfer of oscillating flow around the staggered tube-bundle heat exchanger and verified by experimental results. Effects of the structural and operational parameters, such as the tube length, heat transfer fluid velocity, wave parameters and sinking depth on the thermal performance were analyzed. It was shown that the thermal efficiency of seawater heat exchanger ascended with the increase of wave amplitude and decrease of the heat exchanger sinking depth. Additionally, the tube length and heat transfer fluid velocity could be reasonably designed to achieve the optimum value between cost and performance. The heat transfer mechanism in seawater side was predominated by forced convection to natural convection with the increasing sinking depth under various wave parameters. The proposed model is favorable to delicately characterize the heat transfer of seawater heat exchanger with the consideration of seawater flow. The results in this paper is helpful to guide the optimization on designing the staggered tube-bundle heat exchanger in oscillating flow and to promote the application of ocean thermal energy.

Experimental study on the migration regularity of sand outside a large, deep-water, open caisson during sinking

Based on the sinking construction of the largest open caisson across the world, a sinking simulation test is designed and conducted in this work. Data from sensors during subsidence, the migration track of the sand outside the caisson and the settlement of the riverbed after the sinking are measured and analysed. The relationships between the influence range of sand migration outside the caisson and the sinking depth, and the characteristics of the subsidence space formed after migration are described. Combined with measured data from caisson construction, the migration of sand outside the caisson is concluded to be mainly related to the depth of the caisson and the spatial position of the sand outside the caisson and to be influenced by the seepage force, the blade foot reaction force and the lateral pressure. A calculation model describing the behaviour of the migration is established through dynamic comparison and analysis. It is found that the seepage force, the blade foot reaction force, the lateral pressure, sand gushing and sudden sinking of the caisson are all related to the sand migration. A migration coefficient is defined to describe the migration rate and different degrees of sand gushing and sudden sinking.

Piles and lateral loads: comparison of calculation methods

Introduction. Calculation and analysis of pile resistance to loads remains to be a relevant problem in geoengineering. The design of pile foundations is currently performed using diverse analytical, empirical and numerical methods. However, the reliability of these methods remains to be a topic of interest among researchers and designers. This research paper analyses methods used for calculating the lateral-load capacity of piles in comparison with field-test data. Materials and methods. The paper dwells upon the development of reliable analytical expressions based on mathematical models of the pile–soil interaction. Main existing mathematical models of the soil environment, including the Mohr – Coulomb elastic ideal plastic model and the hardening soil model (HSM) were analysed. A particular attention was paid to a variety of factors affecting the pile–soil interaction, such as natural factors, pile types, pile sinking depth and technology, configurations of loads, as well as time-changed processes. A comparison of methods for calculating the lateral-load capacity of piles was conducted. To that end, calculations using the Mohr – Coulomb model and the local elastic strain theory (still required by building codes) were performed. High-level solid elements were used to develop and compute a finite-element pile-in-soil model in a spatial setting. Another model on the basis of parametric pile elements was designed using the MIDAS software. Results. It is established that the use of numerical calculation methods for evaluating the capacity and movements of pile foundations provides results comparable to those of field tests. These methods demonstrate a higher reliability compared to standardized analytical techniques. Conclusions. The reliability of numerical calculations of pile resistance to lateral impact is shown to be sufficiently high, thus being feasible for use in geoengineering. The use of these methods should be based on advanced non-linear soil models, such as HS, CamClay, etc.