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Fertilizer application has been one of the most important facilities to advance agricultural mechanization. Particularly, manual fertilization cannot fully meet the large-scale production in recent years. In this article, a chain reversal trenching and application device was presented for the organic fertilizer in orchards, in order to enhance the trenching depth and uniform fertilization. A reverse-chain trenching mechanism was employed with a fixed trenching blade that moved in the opposite direction of the chain. The soil cutting and simultaneous backfilling were allowed within the trench, as the device progressed. A trenching depth of up to 600mm was achieved in the chain trenching mechanisms. The separate backfilling was reduced to leave no visible trenches on the surface after completion. This design was also a streamlined operation. The mathematical analysis of the trenching blade was conducted to establish a mathematical model using Cartesian coordinate transformations. The relationship equation was derived for the cutting angle. Optimal angle parameters were also provided. According to the trenching depth analysis, the hydraulic adjustment cylinders were selected for the trenching device. A scrapertype fertilizer application mechanism was adopted to develop the discrete element simulation models for both upright and sideways fertilizer application modes. The fertilizer distribution patterns were analyzed under the two modes. While both modes were similarly distributed fertilizer, and the forward-facing mode was more suitable for the operations with the larger fertilizer widths, while the sideward-facing mode was with the smaller fertilizer widths. In the two fertilizer application modes, the sideways application mode had better uniformity, especially at the lower forward speeds. Therefore, the application mode of sideward-facing fertilizer was selected to ensure that all organic fertilizer accurately fell into the trench. A single-factor experiment was carried out to explore the effects of scraper height, angle, and spacing on the normal contact force and coefficient of variation. All three parameters shared a significant impact on the coefficient of variation. In a coefficient of variation of less than 15%, the optimal height, angle, and spacing of the scraper were selected to minimize the normal contact force, resulting in values of 20 mm, 90°, and 180 mm, respectively. According to these optimal parameters of the scraper, the simulation was conducted to yield a coefficient of variation of 6.02% and a normal contact force of 9.03 N, both of which were lower than those before optimization. Subsequently, a physical prototype was fabricated and field-tested. An average coefficient of variation of 8.34% was obtained for fertilizer distribution, indicating better uniformity. Furthermore, the maximum and minimum fertilizer application tests showed that the quantities ranged from 0.8 to 6 kg/m, thus meeting the fertilization requirements of different plots. The trenching performance tests show that the average trenching depths of two operations were 616.0 and 624.4 mm, respectively, with stability coefficients of 93.57% and 92.58%, respectively, both exceeding 90%. The average trenching widths were 305.4 and 295.4 mm, respectively, with consistency coefficients of 96.16% and 95.04%, respectively, both exceeding 95%. Therefore, the device exhibited excellent performance in the fertilizer distribution and trenching operations, fully meeting the agronomic requirements. The findings can provide a new tool for the deep application of organic fertilizers in orchards, indicating the promising potential prospects. Innovative design and efficiency can also offer valuable insights into the agricultural fields. [ABSTRACT FROM AUTHOR]

When rockfall occurs along dense rock slopes, the rotation direction of rockfall is not always downhill. Specifically, the rockfall may obtain a reverse rotation speed (RRS) after impact under certain conditions, the effect of which on the restitution coefficient (RC) cannot be ignored. According to the statistical results of the reverse rotation (RR) phenomena of blocks obtained from previous experiments, the occurrence of RR is correlated to the block shape, incident angle, and contact attitude. In this study, considering a typically shaped cubic block, the critical condition for the RR is preliminarily deduced. Based on the results, the influence of the RRS on the RC for four typically shaped blocks is examined using a customized device. Results show that the tangential RC (Rt) values of each block are not sensitive to the change in the RRS, the distribution is relatively concentrated and the values are high. Moreover, the normal RC (Rn) values are not sensitive to the RRS, and the distribution is relatively discrete. The RRS influences Rn; however, it is difficult to directly establish the relationship between them. To this end, considering the contact attitude and shape of the block, an integral variable, the impact coefficient (Ic), is proposed to determine the influence of RRS on Rn. Moreover, the impact-bounce behaviours of the block are categorized and analysed. For the block rebound following a single impact, Ic and Rn are positively and negatively correlated when the mass centre of the block (MC) is in front and behind the contact point (CP), respectively. For the block rebound following two successive impacts, with the increase in Ic, the Rn increases. These conclusions help clarify the mechanism of the influence of the RRS on RC and provide vital information and ideas for the development and optimization of a program to accurately predict rockfall trajectories.

Abstract Midgut malrotation is usually present in the early neonatal period with intestinal obstruction and bilious vomiting. However, sometimes it may present later in childhood and adolescence with atypical features and then may remain undiagnosed for long, adversely affecting the growth and development of the child. Here we describe three cases of intestinal malrotation with various atypical presentation and imaging findings.

In order to grasp the reverse startup characteristics of a small radial vane pump in the case of misoperation, a circulation piping system that includes the pump is established. Numerical simulation of the full three-dimensional unsteady incompressible viscous flow is performed based on the slip-grid technique and user-defined functions (UDF). According to the results, the static pressure fluctuation is small at the inlet of the centrifugal pump during the reverse startup, which differs significantly from the forward startup. Compared to the impeller rotational speed, the time required for the shaft power, head and flow curves to reach stability is lagged, with the largest lag being shaft power, followed by head and the smallest flow rate. During the startup, the region where the turbulent kinetic energy mainly occurs changes from the outlet of the volute to the flow path of the impeller. There is no turbulent dissipation rate near the leading edge of the blade; In the early stage of the reverse startup, the similar laws of centrifugal pumps are obviously not applicable. In the later stages of the startup, the similitude law can be basically applied to the performance prediction of centrifugal pumps. [ABSTRACT FROM AUTHOR]

In order to explore the effect of forward and reverse rotation speeds of rockfall on normal restitution coefficient (Rn), three typical blocks of cube, disc and cylinder were customized, and the impact tests of each block with slope at different forward and reverse rotation speeds in X and Y axes were carried out through the specially developed rockfall impact test device. Results show that the rotation speed has no effect on Rn when the disc and the cylinder shaped blocks rotate around the Y-axis (approximately normal impact); when the three shaped blocks rotate along the X-axis (non-normal impact), there exists a certain correlation between the rotation speed and Rn, but Rn is also affected by the block shape and impact posture. Thus, a comprehensive variable - impact posture coefficient (IPC) was introduced to quantify the effect of rotation speed on Rn. In view of the difference of the mechanical action mechanism of normal impact force on Rn under different impact posture, the impact-rebound characteristics of the blocks were classified and discussed. For the type of rebounding after only one impact, IPC and Rn have linear positive correlation and negative correlation respectively when the mass center (C) is behind and in front of the contact point (CP) in the forward rotation test, and the results of the reverse rotation test were just the opposite. For the type of rebounding after two impacts, regardless of forward or reverse, whether C is behind or in front of CP during the first impact, Rn and IPC of each shaped block are strongly positive correlation, yet the relevant laws are not consistent under various working conditions. These conclusions basically reveal the influence of rotation speed on Rn, and provide a reference for accurate prediction of impact-rebound process of rotating irregular rockfall.

Readily available processing hardware and "off-the-shelf" (OTS) simulation software has made "high fidelity" first principles models of both steady and transient states, for both axial and centrifugal industrial compressors, relatively easy to construct. These high-fidelity models are finding their way into "real-time. digital twin" performance monitors, front-end engineering design, and post-design – pre-construction compressor performance evaluation. The compressor models are useful for reliably demonstrating the compressor and – to some degree, based on the complexity of the model – process response to various operating conditions. Once the model is constructed, it is trivial to run a "what-if" analysis of compressor performance to answer questions related to (a) recommendations or validation of the recycle/vent valve size and actuation speed, (b) general piping layout and sizing around the compressor, (c) and hot gas bypass requirements, to name a few. This paper takes a practical approach in discussing the compressor and process parameters necessary for building these dynamic "high-fidelity" industrial-compressor models. We identify compressor inputs and compressor responses that are faithfully modeled by first-principle equations available in the simulation software and those that typically require a compromise between an "ab initio" and data-fitting approximation. We discuss the simulation's tendency to overstate pressure excursions during surge events and understate the compressor operation in the "stonewall" region. We also discuss using the simulator software's compressor-stage enthalpy calculations to predict and quantify the compressor train reverse rotation. We use our broad experience and understanding of the compressor operation and simulation and our experience with the AVEVA™ Dynamic-Simulation "OTS" simulation software as the basis for this discussion.

Copyright of Chinese Journal of Geological Hazard & Control is the property of China Institute of Geological Environmental Monitoring (CIGEM) Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Summary: Low heels are the most common hoof conformational abnormality seen in both the front and hind feet of horses. A low/negative distal phalanx angle in the front feet has been associated with palmar heel injuries but only recently has the significance of low/negative angles in the hind feet received attention. A study including a greater number of horses more representative of the UK horse population would be useful to UK equine practitioners. Our null hypothesis was that the plantar distal phalanx angle does not differ between horses with and without hindlimb lameness. For this prospective case‐controlled study, horses presenting for orthopaedic complaints underwent a complete lameness assessment. The plantar distal phalanx angulation (PDPA), the angle between a line parallel to solar surface contacting the ground and the solar margin of the distal phalanx, was calculated from lateromedial radiographs. Horses were included in the study if hindlimb lameness was definitively localised by diagnostic anaesthesia. Student's t‐tests and multivariable linear regression models were used for statistical analysis. One hundred and eighty‐two horses met the inclusion criteria, 132 with hindlimb lameness and 50 controls. The mean left PDPA for HLL group was −1.0° vs. +1.8° for the controls. The mean right PDPA for HLL group was −1.1° vs. +1.4° in controls (both P<0.001). Lameness was most frequently localised to the stifle (59% of horses), followed by the distal tarsal joints and the proximal suspensory region. A limitation of the study was that the control group included some forelimb lame horses. It was concluded that horses with hindlimb lameness, including lameness localised to the stifle, were more likely to have negative PDPAs. While Pezzanite et al. (2019) previously reported a relationship between negative/neutral PDPA and tarsal/metatarsal lameness, this study is the first to find a relationship to stifle lameness, which may reflect differences in the populations of horses examined. Further kinematic studies are required to determine whether it is a cause or effect relationship. [ABSTRACT FROM AUTHOR]

Recently, small scale H-Darrieus vertical axis wind turbines (VAWTs) have got great attention of researchers and wind turbine manufacturers due to their application at roof-tops of residential buildings. They are generally preferred over horizontal axis wind turbines (HAWTs) in terms of lower levels of noise production, operation at low wind speeds and lower manufacturing costs. But the main problem with such wind turbines is their low efficiency, which is mainly due to the complex flow around the turbine blades. It is of great importance to first fully understand the nature of complex aerodynamics associated with such wind turbines. Present study analyzes the instantaneous tangential velocity (ITV) and its impact on the power performance of H-Darrieus wind turbine at five different tip speed ratios (TSRs) i.e. 1–5. Computational models based on large eddy simulations (LES) have been developed using commercial software SC/Tetra V12. Throughout the numerical simulation, it is found that ITV of single blade has a negative value (reverse rotation) for TSRs 1–3 when the azimuth position ranges from 80° to 140°, whereas it has positive values during the remainder of the rotation for the mentioned TSRs. Furthermore, the magnitude of the negative ITV for a single blade was found to increase from TSR 1 to 3; the maximum value of the negative peak is equal to approximately −17.2 m/s while at the azimuth position of 110° for blade number 1 at TSR 3. On the other hand, no negative value of ITV is found for any of the three blades during a complete rotation at relatively higher values of TSRs i.e. 4 and 5. The possible physical reasons behind this behavior have been explained through aerodynamic forces and 2D color contours of important parameters, such as vorticity and static pressure. Finally, a discussion has been included in the final section of this paper explaining how negative ITV affects the power performance of H-Darrieus wind turbines. The current CFD model has been compared and validated with experimental data. [ABSTRACT FROM AUTHOR]

For the complex astern moving structure of amphibious platform arid its performance study, a new mode of astern moving is presented based on the water-surface hionic vector propeller, and a new amphibious platform is designed. Thr straight astern moving of 0. 7 m/s and the astern steering of small-radiiiH of about 0. 75 rn an; realized by rotating the propeller reversely. A fluid dynamics model of propeller is set up lo analyze the influences of height, spoke length, rotational velocity and blade angle on three-dimensional output performance of astern moving with periodic output. So the study of the flow due to rotating of flat plates is further enriched. And the calculation model is validated hy usin^ the open water test system of vector propeller. The results show that the turning moment decreases with the increase m height lit pmpfller axle; the down push Force and drag force arc linear with the spoke length, and the turning moment is quadratic functions lo spoke length; and three-dimensional driving outputs increase with the increase in rotational velocity of propeller. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Unidirectional dry gas seal may experiences reverse rotation when equipped in a centrifugal compressor. This paper describes how the reverse rotation effects on the spiral unidirectional dry gas seal performance and pressure distribution inside the gas film, also an investigation of using a different herringbone shape grooves configurations has been done using ANSYS FLUENT 14.5 CFD simulation. The influence of decreasing rotational speed to the static condition and rotate in the reverse direction on internal flow and gas seal performance is examined from 10800 to -10380rpm. The results indicate that the internal pressure distribution inside the gas seal in reverse rotation is decreased and the open force consequently decreased by 4%. The modification on the same seal is done to enhance its performance at reverse rotation condition. The herringbone spiral grooves is used with different configuration, the new configurations are examined in the forward and reverse rotation direction. The analysis for the pressure distribution is done and its effect on the seal performance is examined. Seal performance is compared with standard one for all geometrical and operating conditions. At high forward rotational speed 10380rpm, the pressure at the end of the spiral groove is about 11.4% higher than the inlet pressure at the seal outer diameter, while at reverse rotation, the pressure is not increased in radial direction. The open force corresponding to reverse rotation increased with a value 1.5kN for both the 100 overlap and 50% forward overlap seal faces, but using seal face with 50% backward overlap failed to enhance the open force at reversal condition. [Copyright &y& Elsevier]

The current paper describes the experimental determination of a complete four-quadrant map for a three stage low-speed axial flow compressor. Non-dimensional pressure rise and torque coefficients and efficiency characteristics were determined. Six possible modes of operation were identified in the four quadrants. The characteristic for a compressor with a rotational speed of zero rpm, in terms of pressure rise coefficient and flow coefficient, is S-shaped and forms the dividing line between two alternate modes of operation which exist in the second and fourth quadrants. First quadrant operation is only possible during positive rotation, and third quadrant operation during negative rotation, as the zero-speed S-curve passes through the origin and so does not pass through these quadrants. Consequently, only one mode of operation is possible in each of these two quadrants. A system of notation for describing the various modes of operation has also been developed. Second quadrant operation for positive compressor rotation, and fourth quadrant operation with negative rotation are highly dissipative conditions of operation. First and third quadrant operation are compressor-like modes. Second quadrant negative rotation and fourth quadrant positive rotation operation are turbine-like modes. [ABSTRACT FROM AUTHOR]