Longitudinal Movement Research Articles

Remaining Fatigue Life Predictions of Railway Prestressed Concrete Sleepers Considering Time-Dependent Surface Abrasion

One of the safety-critical components of ballasted track systems is railway sleepers whose main functions are to (i) transfer vertical load, (ii) maintain rail gauge, and (iii) restrain longitudinal rail movement. Railway sleepers can be manufactured using timber, concrete, steel, composite, and any other engineered materials. Prestressed concrete sleepers are the most commonly used type worldwide because of their superior value-for-money performance. In practice, railway sleepers experience thousands of cycles of aggressive wheel–rail dynamic loads and wear deterioration can be observed over their service life. Not only does the deterioration affect track quality and geometries, but it also undermines the structural integrity of the track structures. The wear and abrasion directly decrease the capacity of railway sleepers, resulting in the reduction in service life. In this paper, the emphasis is placed on the assessment of the fatigue life of prestressed concrete railway sleepers with imperfect geometry. This study is the world’s first to establish a new fatigue simulation of railway concrete sleepers considering accumulative non-constant amplitudes, which has been validated using full-scale experimental results and empirical analyses. Parametric studies have been conducted to obtain new insights into the fatigue performance of the worn sleepers. The new findings will improve railway sleeper maintenance and inspection criteria, and will provide a new guideline on track-condition monitoring networks.

Influence of Increased Freedom of Movement on Welfare and Egg Laying Pattern of Hens Kept in Aviaries

Simple SummaryThe laying hen industry is shifting from cages to alternative housing systems (such as aviaries) to address societal concerns regarding animal welfare. However, it is important to understand the hens’ needs in these systems, in terms of space use and behaviour, to promote their welfare and avoid drawbacks. Therefore, we examined the effects of three different structural modifications (addition of ramps and/or removal of internal partitions) to increase the hens’ freedom of movement in a commercial aviary system. Higher freedom of movement resulted in positive effects on feather conditions and the possibility of choosing between the aviary tiers according to the hens’ preferences. Laying hen producers may therefore adopt some of these structural modifications in aviary systems to enhance the welfare of hens.This work investigates the effects of structural modifications on the welfare level and laying patterns of hens in a three-tier commercial aviary system. Four experimental groups were used: C (control, housed in a traditional aviary); LM (longitudinal movement, in which internal partitions were removed); VM (vertical movement, in which ramps were installed); and FM (freedom of movement, both LM and VM modifications). Hens showed worse body condition scores (p < 0.05) in all the modified aviaries, while plumage condition was improved in FM but worsened in VM (p < 0.05). No significant effect was observed on egg deposition patterns, egg quality or keel bone damage. When ramps were available (VM and FM groups), hens reduced the number of flights and increased the number of walks from 0.52 to 7.7% of the displacements on average (p < 0.05). Apart from some feather pecking concerns in VM (likely due to overcrowding in some favourite aviary areas), LM and FM seemed to facilitate animal movement and promote species–specific behaviour. It is concluded that hen welfare in aviary systems can be improved by means of tailored structural modifications. Producers may therefore adopt some of these modifications (providing ramps and/or removing vertical barriers) to enhance the welfare of hens.

The Experimental Evaluation of Cone Wedge Shape based Electronic Wedge Brake Mechanism in Vehicle Braking System

The brake system is one of the most critical parts of a vehicle's technology for avoiding accidents. The ultimate focus of the braking system is to guarantee that adequate stopping force is available to stop the vehicle's longitudinal movement. Therefore, the ability of a brake system to stop a vehicle must be examined in terms of analyzing the brake system's performance and the implementation of the brake system on actual vehicles. This study offers a performance evaluation of the Electronic Wedge Brake based on the Cone Wedge Shape (CW-EWB) on the vehicle brake systems. The evaluation was carried out through dynamic assessments, namely sudden braking tests at constant speeds of 40, 60, and 90 km/h using the MATLAB Simulink software simulation method and an experimental study using hardware-in-loop simulation (HILS). In the simulation study, the performance of the vehicle brake system using CW-EWB was compared with the brake performance of the vehicle using the conventional hydraulic brake (CHB). The results showed that CW-EWB behaved similarly to the hydraulic brake in terms of required brake torque output but with a faster response time, i.e., between 0.5 – 1 s. The HILS experimental study was conducted to evaluate the performance of the CW-EWB on actual vehicles. This method confirmed the HILS results against the simulation results with a variable response time of less than 6%. Vehicle body speed, wheel speed, longitudinal tire slip, and stopping distance experienced by the vehicle were all evaluated. The study's findings show that the proposed CW-EWB is quite effective and sufficiently dependable to be used as a vehicle brake system, notably in Antilock Braking Systems.

Двухконтурный рекуперативный теплообменный аппарат с межканальным движением теплоносителя в металлических сетчатых материалах

The paper considers a dual-circuit recuperator using the principle of interchannel movement of coolant through a porous metal mesh. This interchannel coolant movement schematic and the metal mesh manufactured via vacuum diffusion welding of woven metal meshes form the basis for developing compact high-performance recuperators for aircraft. Employing porous metal mesh materials characterised by a well-developed heat exchange surface and transitioning from conventional longitudinal coolant movement within channels to interchannel coolant movement through metal meshes are the factors that ensure operation at low Reynolds numbers and maximum heat exchange efficiency. The principle of interchannel coolant movement combined with the intermesh coolant movement within the metal mesh yields a highly efficient porous heat exchange path, leading in turn to developing a recuperator featuring interchannel coolant movement that will enable greater heat exchange efficiency than that provided by the best finned heat exchangers.

Addressing unobserved heterogeneity at road user level for the analysis of conflict risk at tunnel toll plaza: A correlated grouped random parameters logit approach with heterogeneity in means

Toll plaza is a designated area of controlled-access roads like expressway, bridge, and tunnel for toll collection. A number of toll booths are often placed at the toll plaza accommodating high passing traffic and multiple payment methods. Traffic and safety characteristics of toll plazas are different from that of other road entities. Different conflict risk indicators, which are usually longitudinal, have been adopted for real-time safety assessment. In this study, correlated grouped random parameter logit models with heterogeneity in the means are established to capture the unobserved heterogeneity, with additional flexibility, at road user level for the association between conflict risk and influencing factors. In addition, modified conflict risk indicator is developed to assess the safety of diverging, merging, and weaving movements of traffic, with which vehicles’ dimensions (width and length), and longitudinal and angular movements are considered. Also, prevalence and severity of both rear-end and sideswipe conflicts are assessed. Results indicate that toll collection type, vehicle’s location, average longitudinal speed, angular speed, acceleration, and vehicle class all affect the risk of traffic conflicts. Furthermore, there are significant correlation among the random parameters of severe traffic conflicts. Proposed analytic method can accommodate the conflict risk analysis for different conflict types and account for the correlation of unobserved heterogeneity. Findings should shed light on appropriate remedial measures like traffic signs, road markings, and advanced traffic management system that can improve the safety at tunnel toll plazas.

Distributed cooperative trajectory and lane changing optimization of connected automated vehicles: Freeway segments with lane drop

This study presents a methodology for optimal control of connected automated vehicles (CAVs) in freeway segments with a lane drop. Lane drops can create bottlenecks with a considerable number of mandatory and discretionary lane-changing maneuvers when traffic volume is high, which can eventually lead to stop-and-go conditions. Proper motion planning aligned with optimal lane changing upstream of a lane drop can increase capacity and reduce the number of stops and the risk of collision. This paper introduces a vehicle-level mixed-integer program to control longitudinal and lateral movement of CAVs, provide a smooth flow of traffic, and avoid congestion in freeway segments with lane drops. To ensure the feasibility of vehicle-level decisions and promote system-level optimality, a cooperative distributed algorithm is established, where CAVs coordinate their decisions to find the optimal longitudinal and lateral maneuvers that avoid collisions among all vehicles. The proposed coordination scheme lets CAVs find their optimal trajectories based on predictive information from surrounding vehicles (i.e., future locations and speeds) and coordinate their lane-changing decisions to avoid collisions. The results show that optimal lane changing of CAVs smoothens the traffic flow and increases freeway capacity in congested traffic conditions. Compared with all-knowing CAVs simulated in Vissim, the proposed methodology reduced the average travel time by up to 86.4%. It increased the number of completed trips by up to 134.3% based on various traffic demands and lane drop layout combinations.

Research on decoupling control for the longitudinal and lateral dynamics of a tractor considering steering delay

To enhance the efficiency of tractor operation, the longitudinal and lateral dynamic control of a self-driving tractor is studied in this paper, and a control system that decouples control of the longitudinal and lateral movement of the tractor is proposed. The trajectory controller calculates the desired speed and desired yaw rate signals of each subsystem, and a PID controller regulates the longitudinal speed of the tractor. A pure pursuit algorithm calculates the desired front wheel angle of the tractor. To decrease the system time delay in the automatic steering system, an automatic steering scheme based on improved Smith predictive control is proposed. Through decoupling control of the longitudinal and lateral controllers, the tractor’s path tracking performance is assured.

Evaluation of biventricular longitudinal myocardial function in normal fetuses at different gestational ages using ultrasonic velocity vector imaging.

ObjectiveThis study aimed to evaluate biventricular myocardial function and biventricular longitudinal global myocardial function of fetuses at different gestational weeks using ultrasonic velocity vector imaging.MethodsA total of 127 pregnant women were enrolled and divided into five groups according to the gestational age of their fetuses. The velocity, strain, and strain rate of the left and right ventricles were measured, and these biventricular parameters were compared between the groups. The global parameters of the biventricular myocardium were also compared.ResultsA pairwise comparison revealed that the differences in biventricular velocity and strain rate between groups in adjacent gestational weeks were not statistically significant (P > 0.05), but velocity increased with gestational age. A comparison of fetal longitudinal global myocardial parameters revealed that the global velocity, strain, and strain rate of the right ventricle were higher than those of the left ventricle, and the differences were statistically significant (P < 0.05) in all groups.ConclusionThe peak velocities of the fetal left and right ventricles increased with gestational age, but the global strain and strain rate did not, suggesting that fetal myocardial function is mature and constant in the middle and late stages of pregnancy and can more reliably reflect myocardial deformation. The peak systolic velocity, global strain, and peak strain rate of the right ventricle were higher than those of the left ventricle, suggesting that the right ventricle dominates longitudinal systolic movement from the second trimester of pregnancy.

Revealing migration schedule and potential breeding grounds of Lined Seedeaters using citizen science data

ABSTRACT The Lined Seedeater (Sporophila lineola) is a small intra-tropical migrant songbird. However, little is known about its breeding and wintering grounds, or migratory habits. To investigate potentially distinct breeding populations and the migratory schedule of Lined Seedeaters we analysed its spatial and temporal distribution using published breeding records, museum vouchers, and data from citizen science projects (eBird and WikiAves). Our findings suggest that there are three main breeding areas: northern Argentina and north-western Paraguay, south-eastern Brazil, and north-eastern Brazil, and that the breeding season seems to be restricted to November through May, with slight differences in timing among these three areas. The species winters in the northern part of South America (mostly in grassland areas) and maybe also in the Amazonia. Moreover, rainfall predicts the latitudinal and longitudinal movements of Lined Seedeaters, with the migratory movements associated with an increase in rainfall. Taken together, these results provide a first comprehensive overview on the migration of Lined Seedeater, calling for further empirical field studies. Understanding intra-tropical migratory patterns is paramount to comprehend the potential impacts of environmental change in tropical ecosystems.

Hypoglycaemia and rebound hyperglycaemia increase left ventricular systolic function in patients with type 1 diabetes.

To investigate echocardiographic changes during acute hypoglycaemia followed by recovery to hyperglycaemia or euglycaemia in patients with type 1 diabetes. In a randomized crossover study, 24 patients with type 1 diabetes took part in two experimental study days, consisting of a hyperinsulinaemic-euglycaemic phase (5.0-8.0 mmol/L) for 45 minutes followed by a hyperinsulinemic-hypoglycaemic phase (2.5 mmol/L) for 60 minutes, and a recovery phase in either hyperglycaemia (20 mmol/L) or euglycaemia (5.0-8.0 mmol/L) for 60 minutes. Cardiac function was evaluated with echocardiography during each phase. Acute hypoglycaemia increased all markers of left ventricular (LV) systolic function, including LV ejection fraction (LVEF), global longitudinal strain (GLS), GLS rate and peak systolic velocity of mitral annular longitudinal movement (s'; P < 0.001 for all). During the recovery phases, all markers of LV systolic function were increased during hyperglycaemia (P < 0.01 for all), and LVEF and GLS remained increased during euglycaemia (P=0.0116 and P=0.0092, respectively). The increment in LVEF during the recovery phase was greater during hyperglycaemia than euglycaemia (P=0.0046). Hypoglycaemia, recent hypoglycaemia, and overcorrection of hypoglycaemia to rebound hyperglycaemia increased LV systolic function in type 1 diabetes and may imply consideration of plasma glucose when evaluating LV function in patients with type 1 diabetes. An increase in LV systolic function may cause increased strain on the heart and partly explain the link between hypoglycaemia, high glycaemic variability and cardiovascular disease.

3D Printed Ultra-thin Acoustic Metamaterials with Adaptable Low-frequency Absorption Performance

The inherent absorption frequency of traditional sound absorbers makes it difficult to solve the problem of acoustic wave removal in a changeable acoustic environment. In this study, acoustic absorption metamaterials (AAMs) with adaptable sound absorption performance were innovatively designed using the structural combination concept and fabricated via 3D printing. Accordingly, two coiled-up channels were combined in a single cell, which could effectively broaden the absorption bandwidth in a limited space. The longitudinal movement of the coiled-up channels endowed the tunable entire depth and internal cavity of the AAMs; thus, the sound absorption performance could be tailored accordingly. Through computational analysis and experimental verification, it was demonstrated that the depth of the AAM could be adjusted from 10 mm to 20 mm, and the corresponding absorption frequencies of the two channels ranged from 206 Hz to 179 Hz and 379 Hz to 298 Hz, respectively. In addition, the finite element results also indicate that the sound absorption bandwidth of AAMs could be further improved by the periodic arrangement of the units. This work opens a promising structural design approach for presenting a route toward acoustic devices with adaptable absorption performances.

Optimum seismic design of curved cable-stayed bridges

One of the current advances in cable-stayed bridges design is the ability to create curved geometries to fulfill architectural requirements or site constraints. There are currently 68 curved cable-stayed bridges under operation, 56 of which have been completed in the current millennium. Most of them are footbridges, but the number of road and railway applications is increasing. However, there is not much information concerning the design of these structures. This paper concerns a 350 m long curved cable-stayed road bridge with a special emphasis on the seismic optimum design. The tower-deck connection is a key aspect for the seismic response. The longitudinal movement between tower and deck is released, the transverse and vertical support stiffness and damping are considered as design variables. For this structural-control optimization, linear viscous dampers are sought. The spatial variability of the seismic ground motion and construction erection stages for curved CSB are considered. An entropy-based algorithm is used to find the optimum solutions for two designs, S1 where the seismic loading is scaled to 30% and S2 with full seismic intensity. The results show that optimum design S2 costs 21.5% more than S1 optimum and 43% more than a similar straight bridge.

Implicit intention communication as a design opportunity for automated vehicles: Understanding drivers’ interpretation of vehicle trajectory at narrow passages

To ensure road safety in mixed traffic, automated vehicles (AVs) must be equipped with distinct and easy-to-understand communication strategies. For this, the communication design of AVs might be oriented toward implicit communication between manually driven vehicles. This research focused on how drivers interpret observable vehicle behavior (vehicle trajectory) to predict vehicle intentions and planned maneuvers. In addition, the processing and interpretation of contradictory cues were examined as a possible cause for misunderstandings and failed coordination. Two video-based experiments investigated the presumed intention (yielding or insisting on priority), intention recognition time, distinctiveness, and cooperativeness of a vehicle’s implicit communication at narrow road passages. For this, two vehicles approached a bottleneck from opposite sides, and only one vehicle could pass at a time. The driving behavior of the oncoming vehicle consisted of longitudinal (decelerating, stopping, accelerating, maintaining speed) and lateral movements (driving to the center, driving to the edge of the road, no lateral deviation) at different timings (early, late). The results indicated advantages of lateral vehicle movements for distinct intention communication. Lateral movements were interpreted the fastest, perceived more distinct, and were more decisive for the presumed intention than longitudinal movements. Early communication was preferred by drivers but increased the intention recognition time, especially for longitudinal movements. However, early lateral communication was interpreted as fast as late longitudinal communication. Furthermore, lateral and longitudinal vehicle movements within a driving pattern that contradicted each other led to ambiguous perceptions. For AVs, early distinct communication via lateral vehicle movement is recommended. Minimizing ambiguity in the interpretation of communication cues might maximize the probability of the safest response from human drivers and contribute to accident prevention in mixed traffic.

Determining the direction of the mining face direction during development of ravines pit surface

Purpose. Establish an effective direction of the mining front direction in the beams locations at the development of a placer mineral deposit. Research methodology. The analytical method of research was used at the development of a method for determining the time of mining a pit section with a crossed beam surface when applying schemes with longitudinal and transverse movement of the mining front. The graphical method was used to analyze the established dependences of the maximum allowable cutwidth into the rock mass on the length of the open pit when determining the effective scope of the scheme with the longitudinal direction of the mining front at the development of placer deposits. The results. Schemes for mining a pit section with a cross-beam surface have been developed, providing for the longitudinal and transverse direction of the mining front, which make it possible to determine the main parameters of the mining system elements and establish the term of pit life. Efficient parameters have been established for the use of the transverse and longitudinal directions of mining faces movement when a pitsection with rugged terrain, which makes it possible to reduce the labor intensity of the process by 150–220 machine-shifts of an excavator at the pit field length of 300 to 900 m. Scientific novelty. The influence of the open pit length on the maximum allowable cut width into the rock mass during the longitudinal movement of the mining front is determined. The results of the research allow to establish that with an increase in the open pit length from 300 to 900 m, the maximum allowable width of the cut into the rock mass during the longitudinal movement of the front increases from 140 to 740 m. Practical value. A method for determining the time of mining a pit section with a crossed beam surface when using schemes with longitudinal and transverse movement of the mining front has been developed. The use of the proposed method makes it possible to determine the effective direction of mining front movement, depending on the parameters of the development system pit elements.

Tricuspid Annular Abnormalities in Isolated Left Ventricular Non-compaction-Insights From the Three-dimensional Speckle-Tracking Echocardiographic MAGYAR-Path Study.

IntroductionProminent trabecular left ventricular (LV) meshwork and deep intertrabecular LV recesses are featuring LV non-compaction (LVNC). The aim of this study was to evaluate tricuspid annular (TA) morphological and functional abnormalities by three-dimensional speckle-tracking echocardiography (3DSTE) in patients with LVNC without right ventricular (RV) involvement.Materials and MethodsThis study consisted of 21 patients with isolated LVNC, from which 6 cases were excluded due to inferior image quality. The remaining patient group consisted of 15 subjects with a mean age of 52.1 ± 11.4 years (9 males). LVNC was defined according to the Jenni's criteria. Their results were compared to 21 age- and gender-matched healthy controls (mean age: 52.4 ± 3.9 years, 14 males). Complete routine 2-dimensional Doppler echocardiographic examination was performed in all the patients with isolated LVNC and healthy controls. End-systolic and end-diastolic TA dimensions were assessed on selected planes derived from full-volume 3D echocardiographic datasets during 3DSTE.ResultsPatients with isolated LVNC showed significantly dilated end-systolic and end-diastolic TA diameter and area, which were accompanied with preserved TA functional properties and associated with right atrial (RA) volumes. TA plane systolic excursion (TAPSE) showed mild correlations with TA fractional area change (TAFAC) and TA fractional shortening (TAFS). No correlations could be demonstrated between TAPSE and TA morphological features. Extent of LVNC did not correlate with any echocardiographic parameters.ConclusionTA is dilated with preserved sphincter-like function in patients with isolated LVNC. Longitudinal (TAPSE) and sphincter-like (TAFAC and TAFS) TA movements correlate with each other. TA dilation is associated with an increased RA volumes respecting cardiac cycle.

Structure and mechanical properties of hot rolled sheets of Al – 2% Cu – 2% Mn – 0.4% Si – 0.2% Zr alloy subjected to friction stir welding

On the example of a hot-rolled sheet of aluminum alloy Al &ndash; 2Cu &ndash; 2Mn &ndash; 0.4Si &ndash; 0.2Zr% (wt.), the possibility of obtaining joints providing high mechanical properties and thermal stability by friction stir welding (FSW) is considered. From a non-homogenized ingot with a thickness of 40 mm from this alloy a sheet with a thickness of 4 mm was obtained on a laboratory rolling mill at a temperature of 350 оC (reduction degree 90 %). After rolling, cards were cut out of the sheet, which were joined by the double-sided STP method in two modes. For mode 1, the pressing force of the tool was 7551.12 N at a speed of longitudinal movement of the tool of 0.3 m/min, and for mode 2 &mdash; 7256.92 N and 0.125 m/min. The tool rotation frequency for the two modes was the same &mdash; 800 rpm. The structure and properties of the joints were studied before and after annealing at a temperature of 400 оC for 3 hours. It was found that the experimental alloy has high thermal stability, due to which, after FSW in the weld and heat-affected zones, the decrease in hardness does not exceed 10 % and remains practically unchanged. after annealing. It is shown that the FSW method makes it possible to obtain a high quality of welded joints, retaining almost the original strength (&sigma;w = 280&ndash;290 MPa) with a significant increase in relative elongation (&delta; from 3 to 12&ndash;16%). The increase in plasticity is due to the formation of an ultrafine-grained structure in the weld zone (grain size less than 5 &mu;m), which can be explained by the occurrence of dynamic recrystallization during the FSW. The totality of the results obtained allows to consider the use of the FSW method to be promising for obtaining equal-strength and thermally stable joints of rolled sheets of experimental alloys of the Al &ndash; Cu &ndash; Mn (Si, Zr) system, the structure of which differs from the grade alloys of the 2xxx series by a higher content of Mn-containing dispersoids. This work was supported by the Russian Science Foundation grant No. 20-19-00249.

Blue catfish population characteristics and dispersal along a Great Plains river gradient

AbstractUnderstanding movement and dispersal dynamics of mobile, large‐river fishes is essential to adopting an ecologically relevant spatial scale for research and management. Movement and dispersal patterns of Blue CatfishIctalurus furcatus, a large‐river specialist, have been mostly investigated in large river systems within their native range, with little emphasis on tributaries and the influence of connectivity. Here, we examine longitudinal movement patterns, natal environments, and population demographics of Blue Catfish in a tributary system of a large Great Plains river. Blue Catfish tagged in the Kansas River were recaptured in five different rivers of varying size and order, and individual movement was highly variable (0–475 rkm). Adult fish (&gt;400 mm) collected within segments (i.e., Segment 1 and 2) of the Kansas River with connectivity to the Missouri River displayed relatively equal natal contributions from the Kansas River (34–48%) and Missouri River (38–65%) while disconnected river segments contained a high percentage (64–87%) of individuals that originated from reservoirs located on tributaries to the Kansas River. The Kansas River segments (Segment 1 and 2) connected with the Missouri River had lower instantaneous mortality (Z = 0.19, SE = 0.05) and higher proportions of large fish (PSD‐M = 9 &amp; 11, PSD‐T = 3 &amp; 5, respectively) compared to disconnected reaches (Z = 0.27, SE = 0.08; PSD‐M = 3, PSD‐T = 0). Mean length of Blue Catfish collected in disconnected reaches were greater than those from connected reaches for individuals at age‐3 and age‐6, and relatively equal at age‐10. Our data provide additional resolution to movement and dispersal patterns of Blue Catfish within large‐river tributary systems, highlight the role of localized reservoir stock contributions, and illustrate species plasticity across varying levels of river network connectivity.

Segmented trajectory planning strategy for active collision avoidance system

This paper presents a segmented trajectory planning strategy for active collision avoidance system. Considering the longitudinal and lateral movement of the obstacle vehicle, as well as the ego vehicle and obstacle outer contour limitations, the collision avoidance trajectory is divided into three segments: lane changing, overtaking and back to original lane. The starting point and end point of lane-change are decided based on longitudinal and lateral safety distance model according to the relative speed and distance as well as the outer contour of the two vehicles. Based on system objective function and lane-change trajectory cluster, vehicle states, dynamic constraints and vehicle body kinematics constraints, the optimal trajectory can be selected, which can monitor the relative location of the obstacle vehicle constantly and then ensure the vehicle can accomplish the collision avoidance safely and smoothly. Simulation and experiment results demonstrate the effectiveness and feasibility of proposed trajectory planning strategy for the active collision avoidance.

Effects of Green Manure Combined with Phosphate Fertilizer on Movement of Soil Organic Carbon Fractions in Tropical Sown Pasture

The application of green manure is a common way to increase the soil’s level of total organic carbon (TOC) and its fractions. However, the amount of green manure to apply and how the combined application of phosphate fertilizer affects the movement of TOC, and of its fractions, is still unclear. We conducted a column experiment with two treatments of phosphate fertilizer (with and without) and green manure (0, low amount level, high amount level). The longitudinal movement distance and accumulation amount of each organic carbon fraction were investigated after 14 days and 28 days. The results indicated that green manure, phosphate fertilizer, and incubation time affected the movement of the soil organic carbon fractions by affecting the initial quality of the green manure (TOC, cellulose, and lignin content), as well as the changes in quality. Green manure significantly increased the accumulation amount of the organic carbon fractions in the soil, and the high-level input of green manure increased the movement distance and accumulation amount of the organic carbon fractions; phosphorus fertilizer did not have a significant effect on the movement distance of the organic carbon fractions, but it did significantly affect accumulation amount. The 28-day incubation period increased the movement distance and the accumulation amount of the organic carbon fractions, with the exception of the particulate organic carbon (POC), compared to the 14-day incubation period. Taken together, these findings suggest that the high-level of input of green manure combined with the application of P fertilizer is beneficial for increasing the movement of the organic carbon fractions to the depth of the soil, and promotes their accumulation, which is an important agronomic management strategy for improving soil acidity in tropical regions.

Correlations on weakly time-dependent transcritical white-hole flows

We report observations made on a run of transcritical flows over an obstacle in a narrow channel. Downstream from the obstacle, the flows decelerate from supercritical to subcritical, typically with an undulation on the subcritical side (known in hydrodynamics as an undular hydraulic jump). In the Analogue Gravity context, this transition corresponds to a white-hole horizon. Free-surface deformations are analyzed, mainly via the two-point correlation function which shows the presence of a checkerboard pattern in the vicinity of the undulation. In nongated flows where the white-hole horizon occurs far downstream from the obstacle, this checkerboard pattern is shown to be due to low-frequency fluctuations associated with slow longitudinal movement of the undulation. It can thus be considered as an artifact due to a time-varying background. In gated flows, however, the undulation is typically ``attached'' to the obstacle, and the fluctuations associated with its movement are strongly suppressed. In this case, the observed correlation pattern is likely due to a stochastic ensemble of surface waves, scattering on a background that is essentially stationary.