Flanged acetabular cups were developed with the rationale that, at insertion, they would increase the pressure of the cement and improve penetration of cement into the acetabular bone. Various studies have been inconclusive regarding their effectiveness. In this work, we aimed to eliminate all confounding factors and measure the pressures generated during acetabular pressurization and cup implantation using a simplified steel acetabulum, high precision pressure transducers, proper surgical techniques and two acetabular cups, identical apart from the addition of a flange to one. It was found that the flanged acetabular component did not significantly increase the pressure in the acetabulum and in some cases reduced the pressures generated when compared to an unflanged cup. The addition of a flange did not reduce the pressure differential between the pole and the rim of the acetabulum, nor did it have a significant effect on pressure lost over the cup implantation period. It was concluded that flanged acetabular cups provide no significant improvement in the pressures generated in the acetabulum during acetabular cup implantation. It is hypothesized that the flange may be seen as a design feature intended to slow the insertion of the cup into the cement, thus requiring the surgeon to apply a larger load in order to correctly position the acetabular cup; in this way larger pressure will be generated. AlthougOf all failed THRs, many fail due to aseptic loosening of the cup.The literature on this topic contains limited data regarding the pressures generated at the acetabulum surface and there is contradictory experimental evidence regarding the efficacy of flanged acetabular components.Does the addition of a flange to the acetabular component increase the pressure of the cement at the cement‐bone interface?Does the addition of a flange to the acetabular component affect the pressure distribution at the cement‐bone interface?Is pressure maintained throughout pressurisation and cup implantation and does the addition of a flange significantly affect this?Three key questions were asked:2An acetabulum model was manufactured from stainless steel 304 with a 52 mm hemispherical bore, a diameter to which the acetabulum is often reamed in vivo. Steel was selected as it would provide a very accurate surface for the pressure transducers to lay flush on, a porous model would closer represent the surface texture of the acetabulum; however, the cement should only contact the surface flush with the acetabulum, this would be impossible using a porous model; previous studies use a rubber glove to separate the pressure transducer from the cement but this would invalidate the pressures recorded.A Hivac™ bowl  or a glass bowl and a PTFE spatula were used to mix the cement.A Depuy Smartseal acetabular pressuriser  was used for pressurization of the cement. It was 80 mm in diameter and consists of a silicone hemispherical segment and is designed to seal off the acetabulum cavity with the cement still inside Figure .The acetabular cups were manufactured from HXLPE (highly‐crosslinked polyethylene). A flanged and an unflanged cup were designed so that the only difference between them was the flange. Both had an external diameter of 50 mm and an internal diameter of 28 mm, this would leave a cement mantle of around 1 mm thick if the centres of the cup and the acetabulum cavity were aligned. The flange had a thickness of 1.7 mm and diameter 63 mm ; a high‐viscosity cement frequently used for fixation of the acetabular component was used to implant the acetabular cups. For each experiment two 20 g packets of cement were used as this sufficiently filled the cavity. The cement used has been subject to many previous studies.The assembled rig was mounted into a Shimadzu ADS‐X which was used to apply load. It was fitted with a 1 kN load cell Figure . Note thAll equipment used was manufactured with a tolerance of ± 0.05 mm, with consideration of the design of the rig, the loading was always applied within 0.25 mm from the center of the acetabulum cavity.3The methodology employed here is identical to that of a previously published study.The pressuriser was then removed from the Shimadzu and a cup was placed into the cement. The cup implantation program was started, a load of 50 N was applied until the cement was fully cured Figure . After tFor this experiment, pressurization and cup insertion were performed within the working time advised by the cement manufacturer. Preliminary experiments were used to determine the cup insertion load. These preliminary experiments consisted of implanting flanged and unflanged acetabular cups with various loads ranging from 25 to 75 N. Larger loads caused the unflanged cup to bottom out and smaller loads meant that the flanged cup did not sufficiently enter the cement. Upon observation, a load of 50 N resulted in both cups being suitably inserted into the cavity whilst avoiding contact between the cup and the model acetabulum. Loads used in similar experiments were also around this figure. Although it is unclear, Ørskov et al. seemed to measure a load of 57 N for correct position of unflanged cups and 68 N for flanged cups.The end of cup implantation was taken to be when there was a significant deviation from the average pressure. To allow a more detailed analysis of the continuous pressure curves they were divided into fifths and the pressure at each of these five points in time was taken and used for statistical comparisons. Figure . This tep ≤ 0.05 it was concluded that the pressure data at that time was not normally distributed. A student t‐test was used if both sets of data being compared were found to be normally distributed. If one or both sets of data were found to be non‐normal, then a Mann–Whitney test was used. A difference in the means was considered significant if p ≤ 0.05. This statistical methodology was used for all comparisons of data.A Ryan‐Joiner test was used to test for normality, if 4Typical annotated plots showing cement pressure and temperature over time for both vacuum mixed and non‐vacuum mixed flanged and an unflanged acetabular cup implantation can be seen below Figure . Three pp < 0.05) and no significant change in pressure was observed through time (p < 0.05).The averages and the standard deviations of the cement pressure for each pentile (fifth) of cup insertion, at each angle, for each condition can be seen in Table The addition of a flange had little effect on the magnitude of pressure. There were only three significant differences in the pressures. Firstly, the unflanged cup generated larger pressures in the fourth pentile of cup insertion at 0° for non‐vacuum mixed cement than the flanged cup. The magnitude of this difference was 3.58 kPa, a percentage increase of 14.7% of the pressures generated for flanged cups. The second and the final difference in pressure was for the fourth and last pentiles of cup insertion for vacuum mixed cement at 45° from the direction of forcing. Once again, unflanged cups produced a larger force with a 1.81 kPa difference for the fourth pentile and 2.56 kPa for the final pentile, this is 8.76% and 12.6% increase of the pressure generated by the flanged cup.With the exception of the first and second pentile of cup insertion for an unflanged cup with vacuum mixed cement, there was always a significant difference between the pressure generated at the rim and the pole of the acetabulum during cup insertion Figure .There was no statistically significant drop in pressure for any set of data.Upon closer inspection of the removed cement mantles, it was found that none of the cups bottomed out and the cement mantle was thicker than 2 mm for all repeats at all angles from the direction of loading.5The aim of this study was to answer three questions regarding cement behavior in the acetabulum during implantation of unflanged and flanged acetabular cups. Firstly, it was found that the addition of a flange to the acetabular cup did not increase the pressure generated in the cement at the acetabulum bone surface during cup implantation. There were only three significant differences found in pressure due to the cup design; the unflanged cup generated larger pressures. Secondly, except for the first two pentiles of vacuum mixed, unflanged cup insertion; it was found that the pressure was always significantly larger at the pole of the acetabulum (0°) than at the rim (75°) during cup implantation; there is no evidence to suggest that the addition of a flange significantly reduced the pressure differential. Finally, it was found that there was no decrease in pressure over time for any of the testing conditions.A good bond between the bone cement and bone is a key for the longevity of total hip arthroplasty implants as more interdigitation increases the contact area between cement and bone and thus decreases contact stresses.5.1In 1999, New et al. measured pressures generated in vivo during pressurization and found values of 49 ± 17 kPa and 47 ± 17 kPa for two surgeons.The pressuriser effectively seals the acetabulum cavity, and the viscosity of the cement is still sufficiently small so that the pressure is equalized. At the cup implantation stage, there is a flow of excess cement that must be displaced for correct cup positioning. This flow must be driven by a pressure differential. This flow at the cup implantation stage while the cement is curing may be of importance.5.2In this study, it was found that the pressure at the pole (0°) in the fourth pentile of cup insertion for non‐vacuum mixed cement was larger for unflanged cups, generating a pressure 14.7% larger than flanged cups. The other location of significant difference between the pressures generated was for the last two pentiles of vacuum mixed cup insertion at 45° from the direction of the applied loading. Unflanged cups generated a pressure 8.76% larger than flanged cups in the fourth pentile and 12.6% larger than flanged cups in the final pentile. In an in vitro experiment, Oh et al. found that a flanged cup produced pressures of 1440 kPa at the pole and 1050 kPa at the rim for flanged acetabular cups, and just 113 kPa at the pole and 73 kPa at the rim for unflanged components. This extreme difference is accounted for by the insertion loads for the cups. A force of 2167 N was used for the flanged component and just 113 N was used for the unflanged cup. There was no justification for this difference in the methodology section, presumably it was due to the instrument being used in position‐control mode rather than load‐control. Those results are therefore not comparable with ours nor are they clinically relevant as no surgeon could maintain a 2 kN force.The study reported here is novel in that the methodology included pressurization of the cement prior to cup insertion, thus more closely simulating an in vivo implantation. It is also novel as the whole pressure profile through time was recorded and is reported here, allowing future researchers to refer to this study when a methodology is being designed. Preliminary testing was performed to ensure that the forcing program would not cause “bottoming out” or “flanging out” where some part of the cup comes into direct contact with the acetabulum, preventing further pressurization. Although contact between the acetabulum and the flange was not observed, the cement between the two would have increased the contact surface area between cup and cement, and therefore the pressure generated due to the applied load is reduced. This would account for the unflanged component producing larger pressures.The function of the flange should not simply be thought of to increase the pressures generated in the acetabulum. With the same applied load and a larger projected area (due to the flange) a smaller pressure should be generated, as reported here. Instead, the flange should be seen as feature to slow the insertion of the cup into the cement by reducing the gap between the acetabular cup and the acetabulum through which cement can flow, in this way the surgeon must apply a larger load in order to correctly position the acetabular cup and therefore produce larger pressures. This may explain the discrepancy often seen between the lower pressures generated by flanged components seen in this study and the improved longevity of flanged acetabular cups observed in vivo.With some exceptions stated above, this study found that for the most testing conditions, there is always a significant difference between the pressure at the rim and at the pole of the acetabulum during cup insertion Table . As the There are significant differences between this experimental in vitro study and the clinical in‐vivo setting, however, this study was designed to reduce confounding factors so that concrete conclusions could be drawn. Only one cement was used in this study, more cements should be tested to determine whether the conclusions drawn apply more generally. More work should be done to determine the loading applied in vivo, an instrumented acetabular pressuriser is currently being designed by the authors and further work should be done to determine the force used during cup implantation. During the experiments, measurements of the insertion speed of the cup could have been used to further investigate the effect of the flange on cemented acetabular cup implantation. The outer diameter of the cup used was 50 mm. This is 2 mm larger than should be used for an acetabulum 52 mm in diameter. It is not known what affect the gap between the acetabular cup and the acetabulum has on the pressures generated. Further tests should be performed to determine whether the difference between the diameter of the acetabular cup and the acetabulum makes a significant difference to the pressures generated at the acetabulum surface. The rim of an anatomically correct acetabulum is irregular this would probably lead to larger gaps between the pressuriser and the acetabulum and the cup and the acetabulum. Although the cement penetration was not directly measured it has been shown that penetration is improved with an increased pressure.The results suggest that flanged cups provide no advantage in terms of an increase of the pressure differential between rim and pole. Nor does the addition of a flange increase the pressure magnitude compared to unflanged acetabular cups. The data reported here suggest that unflanged cups may produce a larger cement pressure than flanged cups during acetabular cup insertion for the same insertion load.6The results from this study demonstrate that the flange itself does not increase the pressure of cement in the acetabulum but rather, the increased contact area between cup and cement due to the addition of a flange reduces the pressure generated for the same applied load and slows the insertion of the cup. Therefore, to achieve correct positioning in good time, the surgeon will have to apply a larger load to the flanged cup.The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Alex T. Boote and Philip J. Hyde received research funding from Zimmer Biomet UK Ltd and the EPSRC .


The United Kingdom has one of the poorest lung cancer survival rates in Europe. In this study, to help design and evaluate a single lung cancer pathway (SCP) for Wales, existing diagnostic pathways and processes have been mapped and then modelled with a discrete event simulation. The validated models have been used to provide key performance indicators and to examine different diagnostic testing strategies. Under the current diagnostic pathways, the mean time to treatment was 72 days for surgery patients, 56 days for chemotherapy patients, and 61 days for radiotherapy patients. Our research demonstrated that by ensuring that the patient attends their first outpatient appointment within 7 days and streamlining the diagnostic tests would have the potential to remove approximately 11 days from the current lung cancer pathway resulting in a 21% increase in patients receiving treatment within the Welsh Government set target of 62 days. Delays In Wales, lung cancer survival is poor because of late-stage diagnosis and treatment. Only 14.5% of Welsh lung cancer patients survive for 5 years or more . DiscreOur study therefore provides a case study of how DES has been used to represent the diagnostic pathway for lung cancer patients in a major cancer centre in Wales and to evaluate potential reductions of the time until the start of treatment under different “what-if?” scenarios. In particular, this study is concerned with time savings that can be identified within the diagnostic pathway thus reducing a patient’s time until their diagnosis and their treatment begins. The study does not consider the effect of extra resources (personnel or diagnostic tests) on the current system’s capacity; this could be considered in future research using an adapted form of the simulation model described here.Our study has supported a wider programme of research to design and implement the Welsh single cancer pathway and to identify areas where gains can be made so that a patient’s time to diagnosis and subsequent treatment can be reduced, thus improving patient outcomes. While this study focuses on hospitals in Wales, it is envisaged that the findings can prove insightful for other locations within the U.K. and internationally.We present the article in accordance with the STRESS reporting checklist for discrete event simulation modelling . ABUHB provides primary, community, hospital, and mental health services to approximately 600,000 people living in Blaenau Gwent, Caerphilly, Monmouthshire, Newport, Torfaen, and South Powys.ABUHB was chosen to participate in this study as its cancer services are one of the first in Wales to have implemented Tracker 7 software  into their patient administrative systems (PAS), to track patients prospectively through their entire cancer pathway  meetings, and their decision to treat date. The first treatment that the patient received was also included. Knowing the initial treatment plan allows investigation of whether patients with different treatments spend different lengths of time in the system. The treatment paths considered in the model are chemotherapy (SACT), radiotherapy, surgery, chemoradiotherapy, palliative care, active monitoring, and other (the specific description of this category is not included).Results of a statistical analysis were used to parameterise the simulation model. Stat-Fit for Simul8 and Easy Fit 5.6 Professional used to estimate the statistical distributions associated with the model parameters. In particular, the model uses the inter-arrival rates, and the service times for each clinic appointment and diagnostic test carried out. A full list of the model parameters can be provided on request.The total number of referrals, broken down by current pathway (Urgent Suspected Cancer (USC) and non-Urgent Suspected Cancers (nUSC)), and status (active/treated/downgraded), is provided in Further analysis of the diagnostic test data on Tracker 7 shows that 98% of patients  have three or fewer diagnostic tests  with theConsidering the diagnostic tests, we defineTime to arrangeThe time between the request date and the date when the test was carried out.Reporting timeThe time between the test taking place and the report being produced.Total timeTime to arrange and Reporting time.The sum of the The average times associated with the most prevalent tests used in ABUHB are shown in 2.1.We have built a detailed computer simulation model (using SIMUL8 software) to capture the diagnostic pathway for lung cancer patients within ABUHB. The model allowed us to simulate individual patients on their diagnostic pathway. The sequence of tests in the current lung cancer pathway simulation model is based on the Tracker 7 data alongside input from respiratory consultants and specialist nurses within the health board.Under the current lung cancer pathway , a patieThe simulation model for the current lung cancer pathway  considerThe final section of the simulation model considers the steps involved in each of the treatment options until the patient starts their treatment. For patients undergoing curative treatment, they undergo an outpatient clinic where they consent to their treatment. Following this, the planning and preparatory processes are carried out and these have been captured in the simulation. For example, detailed contour planning is needed for radiotherapy patients to ensure that the correct dose of radiation is applied to the correct area. In the case of chemotherapy patients, blood tests are required to ensure that the white blood count and liver and kidney function are at a sufficient level for the oral or IV drug that will be prescribed. Surgical patients are required to undertake a pre-assessment clinic before they are admitted to hospital for surgery.The simulation model monitored patient progress along the pathway. The model captured the average time in the system and the percentage of patients that are within a certain time threshold. In the current lung cancer pathway model, the time in the system represents the time between the point of referral (POR) by the general practitioner and the time of the first treatment. The target is 62 days.As the pathways are different for patients undergoing different treatment options, the results were captured for each of the main treatment categories  along with palliative care and active monitoring. The numbers of patients classified as either undergoing chemoradiotherapy treatment or other are minimal and not considered in the scenario analysis. In the scenario analysis, the results for the SACT, radiotherapy, and surgery pathways are presented and discussed.2.2.The average time spent on the lung cancer pathway The percentage of patients that spent 62 days or less on the pathway The simulation model was run for 300 iterations to ensure stable predictions of the key performance indicators (KPIs). The KPIs collected for the current lung cancer pathway were:Model validation and verification of the current pathway model ensures that the model sufficiently mimics the current lung cancer pathway implemented within ABUHB. The KPIs from the model were validated against the actual data . The mod2.3.Scenario analyses were also conducted to aid future demand and capacity decisions. For example, scenarios considered the benefits associated with different levels of service provision for the diagnostic tests. Currently, in Wales, there are lengthy delays associated with certain diagnostic tests which can add 2–3 weeks to the patient’s pathway see . This ofOutpatients within 7 daysScenario 1: ), we considered the effect of all patients being seen in an outpatient clinic within 7 days of their date of suspicion, having had their initial CT scan.In the first scenario , we considered the effect of different levels of service provision in the diagnostic tests. In the 7 days between tests scenario we considered the effect of a weekly diagnostic service. In the between tests3 days , we considered a bi-weekly service and in the 1 day between tests, a daily service.In the next three scenarios  consider the effect of reducing the time it takes to report a diagnostic test to 2 days or less. The next two scenarios, Scenarios 5 and 6  patients, Scenario 9 considered the next day outpatient clinic and a more streamlined blood test service. For radiotherapy patients, Scenario 10 considered the next day outpatient appointment coupled with a reduction in the time taken to send out the appointment letters to the patient. For surgery patients, Scenario 11 considered a reduced wait for both their pre-assessment clinic and admission to the hospital.Considering all of these scenarios could examine whether all patients could potentially receive treatment within the 62-day target proposed by the Single Cancer Pathway and possibly the future 49-day target.3.The results for the baseline and scenario models for the current lung cancer pathway are presented. Outpatients within 7 days) considered the effect of ensuring that patients are seen in an outpatient clinic within 7 days of their date of suspicion. If this could be achieved, then 5 days could be removed from the lung pathway. For example, the mean time to diagnosis for surgery patients would reduce from 67 to 62 days  is available.The second scenario, Reported within 2 days) sees a one to two-day reduction in the pathway length. If the reports were available the day after the test (Reported within 1 day), patients could see two days removed from their pathway.Reducing the reporting times associated with diagnostic tests to 2 days (The combined scenarios offer the largest reduction in the pathway length with approximately 9 days removed from the pathway if a patient is seen within 7 days and they are offered diagnostic tests (provided twice a week) and receive the results within 2 days. Eleven days can be removed from the current lung cancer pathway if patients are seen in clinic within 7 days and a daily diagnostic service on offer with reports available the next day.If we combine these scenarios with a time to treatment that is reduced by a quicker outpatient appointment and further tests, we can achieve compliance with the National Optimal Lung Cancer Pathway; 95% of patients diagnosed and start treatment within 62 days. If patients are seen in clinic within 7 days, have tests that are offered twice a week and reported within 2 days, and start their treatment within 21 days, the scenario suggests that the average time in the system drops to 40 days or under for all treatment pathways in each hospital.Outpatients within 7 days) where patients attend an outpatient clinic within 7 days, the percentage of patients receiving their first treatment would increase by 8–10% (see Under the first scenario (–10% see . For exa7 days between tests) where a weekly diagnostic service is offered, there is a slight increase in the percentage of patients that receive their treatment within 62 days at both hospitals. Patients would observe a 2–4% increase. If a daily diagnostic service (1 day between tests scenario) is offered, there is a larger percentage of patients receiving their treatment within 62 days; an increase of between 15% and 18%.Under the second scenario , approximately 2–4% more patients would receive treatment within 62 days of their date of suspicion.Under the improved reporting scenarios .Rapid access to subsequent investigations, with rapid reporting turnaround times, with tests done in parallel rather than sequentially.Radiologists would need to be available to provide same-day/next-day reports on the scans.There would be a need to increase the number of radiographers and radiologists providing the diagnostic tests so that the turnaround times of each test are reduced. Adding resources to the current simulation model could be considered in future research.The time between the MDT to DTT should be a few days at most. In the National Optimal Lung Cancer Pathway, it is at most 3 days.There would also be a need to ensure that the time between the final MDT and the treatment starting is kept to a minimum with waiting lists being managed appropriately so that the waiting time does not exceed 21 days. The single cancer pathway stipulates that patients should start treatment within 21 days of their decision to treat.To facilitate a more streamlined diagnostic service:Further examination of the radiographers and radiologists’ workload is also needed to see how daily tests and same-day/next-day reporting can be achieved in the future. Current research is considering how the capacity of diagnostics would need to change to support the single cancer pathway in Wales. Our findings have been presented back to ABUHB cancer services and the programme board for the Cancer Research UK grant that funded this work and the wider recommendations are being reported to Welsh Government for further consideration.


Arterial compliance assists the cardiovascular system with three key roles: (i) storing up to 50% of the stroke volume; (ii) ensuring blood flow during diastole; (iii) dampening pressure oscillations through arterial distension. In mock circulation loops (MCLs), arterial compliance was simulated either with membrane, spring, or Windkessel chambers. Although they have been shown to be suitable for cardiac device testing, their passive behavior can limit stress‐based testing of arteries. Here we present an active compliance chamber with a feedback control of variable compliance as part of an MCL designed for biomechanical evaluation of arteries under physiological waveforms.The chamber encloses a piston that changes the volume via a cascaded controller when there is a difference between the real‐time pressure and the physiological reference pressure with the aim to equilibrate both pressures.n = 20) of the function of the chamber is presented against compared raw data.The experimental results showed repeatable physiological waveforms of aortic pressure in health (80–120 mm Hg), systemic hypertension (90–153 mm Hg), and heart failure reduced ejection fraction (78–108 mm Hg). Statistical validation  with the reference values in order to shape the given pressure waveform. The active compliance chamber is an advanced tool for MCL applications for biomechanical examination of stented arteries and for preclinical evaluation of vascular implants. The arterial compliance is responsible for the physiological pressure waveform. In mock circulation loops, this effect is incorporated with compliance chambers passively, generating a non‐physiological waveform. Thus, these approaches are not suitable for stress testing of arteries. The active compliance chamber is presented here reproduces a physiological pressure waveform, via a cascaded controller, that benefits stress‐based testing of arteries. Hence, the compliance is dependent on the bulging effect of the material and the pneumatic pressure in the sub‐chamber. In a studyWindkessel chambers are optimal compliance candidates because they use compressible air instead of a membrane/spring. Moreover, they adopt either a three‐elementIn every cycle that pressure oscillations occur and the pressure waveform deviates from the physiological shape, the resulted waveform is nonphysiological. Nonphysiological waveforms overstress the arterial wall in the circumferential, radial, and longitudinal directions. A nonphysiological stimulus leads to a supra‐ or sub‐physiological shear stress within the arterial tissue layers. Since the arterial tissue layers are highly sensitive to stresses, the triggering of such a stimulusIn order to make a leap from the passive to the active state with controllable and variable compliance, an active compliance chamber is introduced as part of an MCL. The MCL is divided into a simulated left ventricle and the arterial segment with mechanical heart valves. The simulated left ventricle provides systolic and diastolic pulsatility, pressure, and volumetric flows. The active compliance chamber is incorporated in the arterial segment to regulate the pressure waveform of arteries during testing. It regulates the arterial compliance by dynamically shifting the volume of the chamber. This is accomplished through a piston that is tuned, via a cascaded controller, to allow highly controllable responses of compliance. In response to the physiology of the simulated left ventricle, the compliance chamber enables nonlinear variable compliance and can shape the reference pressure in real time. It can be defined as a Windkessel with three elements,The present study aims to validate an active controller of the active compliance chamber and presents a novel setup for mechanical testing of arteries in vitro. Particularly, here we analyze an integrated controller that can reproduce any given pressure waveform to its reference shape. This can be beneficial when assessing arteries  and the impact of pressure variations: (i) healthy as a baseline, (ii) hypertension as a major risk factor for vascular diseases,22.1P = 3.5 mm, a piston diameter of Dpiston = 50 mm, a cylindrical length l = 80 mm, a maximum rotary speed urot = 8000 rpm, and a maximum flow rate Qmax = 54 L/min. The MCL was capable of reproducing HRs up to 250 beats per minute (bpm).To realize the performance of the compliance chamber, it was necessary to develop an MCL capable of reproducing the cardiac cycle of systole and diastole, the heart rate (HR), and the stroke volume. This was achieved by placing a servo‐driven piston cylinder , namely simulated left ventricle to provide the left ventricular pressure (LVP) and a pulsatile flow into the circulation Figure . Naturalxy‐plane. It matched the amplitude for the healthy state and remained the baseline for hypertension and HFrEF scenarios. This made it possible to just change the stroke profile of the simulated left ventricle to reproduce different scenarios without changing the elevation of the basins. The flow travels from the arterial to the venous segment and mimics the peripheral vascular resistance by lowering the systemic pressure according to Bernoulli's lawA transparent testing unit with a heated coil was designed to submerge samples in a liquid bath at 37℃ . Therein, long‐term testing of perfused arteries examining the biomechanical response of the arterial wall under physiological conditions is feasible. Pressure data were recorded in the simulated left ventricle (LVP), in the arterial segment (AoP), and the compliance chamber (CoP). Pressure sensors  with a measuring range of −750 to 1500 mm Hg and an error of ±11 mm Hg (0.5%) were used. A mechanical flow probe  was used ranging up to 30 L/min with an error of ±0.3 L/min (1.0%) after the aortic valve. Attached to the arterial segment, the active compliance chamber was placed to accommodate pressure oscillations during the cardiac cycle and continuation of flow during diastole. The connecting red curve in Figure 2O 50.6% (v/v) , a blood analog that matches the viscosity and density of the blood at 37℃.z‐direction below the xy‐plane  and at the compliance chamber (CoP) have the effect that the function of the compliance chamber influences the arterial segment equally. On this basis, the chamber was connected to the pressure sensor between the simulated left ventricle and the testing unit in order to reform the pressure waveform before the tested subjects and avoid delays. In this way, turbulences between the simulated left ventricle and the testing unit that might affect the aortic valve function or induce wall stresses when simulating extreme scenarios can be avoided. Furthermore, the justification for adding the active compliance chamber in the arterial segment is the need to reproduce the compliance similar to in vivo vessels. This means that the valve function and the ARC must be provided for pressure‐controlled mechano‐responses in both systole and diastole. Furthermore, the use of the active compliance chamber in the arterial segment enables the mimicking of sophisticated and unusual waveforms .The compliance chamber was designed similarly to the simulated left ventricle with a servo‐driven piston  enclosed in a cylindrical chamber, and it was connected directly to the MCL to in order to regulate the pressure of the arterial segment  position feedback encoder  that controls the movement of the piston. The piston diameter was pref) was given as the target pressure. This mechanism builds up a cascaded proportional‐integral (PI) controller (see Control Unit), based on pref. The Perror function checks whether the measured pressure pRT differs from the reference pressure pref. The measured pressure pRT in the arterial segment was used to determine the behavior of the compliance chamber. These values were used as feedback and enable the PI controller to match the reference pressure. If (i) the pRT deviates from pref, the Perror is either positive or negative, then the p–V (pressure–volume) relationship and the compliance of the arterial segment change until pRT = pref. If (ii) pRT = pref, the Perror is zero and the pressure remains constant. Thus, the pressure‐dependent arterial compliance curve is converted into a nonlinear curve and the compliance chamber iteratively reforms the reproduced pressure waveform.The term “active” was so named because of the chamber's ability to automatically regulate the compliance of the arterial segment in accordance with the reference pressure waveform. To control the reproduced pressure waveform in the arterial segment, a feedback control mechanism was implemented Figure . The refV over a change in the pressure p, that is C=∂V/∂p.W, by changing the volume V,C is the compliance, dV is the volume change, and dp denotes the pressure change. Due to the rigid walls of the chamber, the vessel distensibility  is characterized by the reversible expansion of the piston and rises a negative slope in the P–V relationship  when pRT > pref the VACC is expanding, and (iii) when pRT = pref the VACC is constant  AX5200 , the operation of both the simulated left ventricle and the compliance chamber was controlled and the measured data were stored. The control concept consists of three cascading controllers Figure  namely tu(t) is the output of the controller. The input of the controller denoted by e(t) is the difference between the measured pRT and the setpoint value pref, while pk is the proportional gain, and iT is the integrator time constant to be tuned. Table The mechanism builds a movement profile based on the reference function. Each of the above controllers is made up of a PI controller and an anti‐windup scheme. The PI controller can be represented bye(t) leads to the large signal u(t). Since this signal cannot be introduced to the system with physical restrictions or safety requirements, the settling time is increased and large overshoots or undershoots or both can occur.u(t) of the higher‐level controller is the reference of the lower‐level controller, for example, the position controller produces the speed reference for the speed controller. Chamber's target position, the position that the piston should move to, needs to be introduced to the position controller. The value that indicates the actual position of the compliance chamber is provided by the integrated high‐resolution position encoder.The anti‐windup scheme is built into the design of the controller in order to mitigate the undesired effect created by an overreaction of the integrator. This effect, which is referred to as “integral windup,” is due to the fact that the large tracking error After a system of units has been used that defines the position zero point and the division of the motor revolutions over a certain number of positioning units, the distance covered can be specified using physical units. If the actual position does not match the position setpoint, the controller outputs a signal that influences the motor so that the actual position reaches the setpoint. This so‐called closed control loop is also used for speed and current control. It should be noted that the actual speed of the piston is also derived from the information of the above‐mentioned encoder. The torque control, with which the torque requirement of the speed controller can be met, is implemented via the current controller. The motor current used for this controller is also measured with high resolution. The cascaded controller leads to motion control, which means that the actual volume in the simulated left ventricle and the actual pressure in the compliance chamber follow the corresponding reference profile.pref(t) and volume Vref(t) of all hemodynamic scenarios  to PLC and control various hemodynamic parameters . Similarly, other scenarios can be reproduced. The reference functions include pressure and volume values over time, including systolic–diastolic pressure and stroke volume as presets derived from the literature. In addition, the systole–diastole amplitudes and duration can be varied manually directly at the interface by “stretching” the reference waveforms. Furthermore, the stroke volume is defined as the distance of the simulated left ventricle piston that is to be covered according to the closed control loop described by the position‐based controller. HR is expressed in bpm and is inversely correlated with the duration of the cardiac cycle, that is, when the HR increases, the length of the cycle decreases and vice versa. Scenario transitions were achieved by uploading the respective pressure and volume function during operation. The PLC has automatically transformed the profile pref(t) and Vref(t). With each transition , the MCL changed the movement profile from the simulated LV and the active compliance chamber  with high steady‐state repeatable results indicating that the compliance chamber achieved the indicated waveforms. In this study, a data cycle for the hemodynamic profiles is graphed to indicate the accuracy of the waveforms. The healthy referenceThe compliance chamber offers the possibility to read the actual pressure of the MCL and to correct it with the reference pressure in various hemodynamic profiles. Tested under healthy state, hypertension, and HFrEF, the chamber automatically regulated its position and simulated the specified reference pressure, eliminating valve‐related oscillations. To assess the reliability of the active compliance chamber for long‐term performance, the following experimental procedure was used: the circulation was filled with glycerin until the arterial segment reached a systemic pressure of 75–80 mm Hg. For each profile, the reference volumetric values, HR, and the stroke volume were tuned for the simulated left ventricle, while the reference pressure values were tuned for the compliance chamber. Between the profiles, the compliance chamber required three cardiac cycles for the transition and adapted to the reference pressure. This experiment was repeated four times (x¯) ± standard deviation (σ) of aortic and compliance pressure of all three profiles  and test‐1 (AoP‐ACC activated), are plotted to project the significance of the data. For both tests, 20 consecutive cardiac cycles were measured for the healthy state and x¯ ± σ was calculated. The x¯ ± σ values of the raw data and the pressure were calculated in GraphPad Prism 8.0 .Compared raw data 33.1pRT with the reference pressure values pref. It can be seen that the actual and the reference values from the active compliance chamber were balanced throughout the cardiac cycle, except when the valves open/close, which is inevitable.Figure n = 20) reproduced a measurement every millisecond. x¯ ± σ of test‐0 (blue waveform) shows a high σ = 2.4 mm Hg (light blue) between cycles. The pressure feedback with the cascaded controller (test‐1) with low σ = 0.19 mm Hg (light red) shifted the amplitude and eliminated the oscillatory behavior.The statistical comparison of the measured raw data between the reproduced AoP with activated compliance chamber (red waveform) and with deactivated compliance chamber (blue waveform) is plotted in Figure 3.2An optimal physiological condition with an HR of 60 bpm, a stroke volume of 0.07 L/s, and AoP (80–120 mm Hg) was used as a reference.3.3The transition to hypertension3.4pref = 107 mm Hg). The compliance chamber stroke moved in the opposite direction compared with the previous two scenarios  has a profile with a lower ESP and a stroke volume ≤50% than of the healthy scenario, followed by an increased HR from 60 to 80 bpm.s Figure . During 4Conventional MCLs are intended for the evaluation of active and passive cardiovascular implants. The setup presented is inspired by the principles of MCLs with a modified compliance chamber aiming at testing arteries and stents from a biomechanical perspective. This study validates an active approach of a compliance chamber to simulate the arterial compliance in vitro integrated into an MCL. We have presented how the nonlinear compliance of the compliance chamber can reform the arterial pressure in its reference waveform regardless of the ventricular profile that the MCL is generating. The advantage of the active chamber is that the pressure‐volume ratio of the arterial segment is adjusted until the actual pressure is balanced with the reference pressure. Therefore, the volume of the compliance chamber, as it occurs in the Windkessel chambers, does not have to be predefined. Furthermore, no membrane/spring is required as the piston can move freely in the chamber and regulates the volume automatically. Defined as a three‐element Windkessel with nonlinear arterial compliance and adjustment of the resistance of the system to gravity. The three‐element Windkessel approach can adequately embody the arterial system and the pressure–volume relationships compared with its advanced successors, as described in detail by Westerhof et al.Biomechanical examination of arteries, stented or nonstented, requires accurate and controllable pressure waveforms to study arterial changes in the wall that are solely influenced by pressure variations and stenting. Testing arteries in a healthy state (baseline), hypertension, reduced systolic pressure (HFrEF) could provide new insights into how the stented arterial wall is affected and how supra‐ and sub‐physiological stresses can change the matrix homeostasis of the arterial tissue under these pressure shifts. Systemic hypertension was chosen because it is considered to be one of the main risk factors for vascular diseases such as aortic aneurysms treated with endovascular stent‐grafts.While MCLs with passive compliance approaches rate cardiac devices satisfactorily, they may not be suitable for stress‐based artery testing or stent durability testing. So far Pantalos et al.For the intended purpose, the developed compliance chamber is viewed as an advance over the previously mentioned membrane‐based approaches and the typical Windkessel chambers. Because of the complex nonlinear properties of the arterial wall, the P–V relationship can be quite complicated. Translating this relationship in vitro is quite difficult given the rigid walls of the MCL. Instead, the complex viscoelastic properties of the arterial wall that shape the pressure waveform can be simplified. In our setup, the controller actively simulates arterial distensibility by changing the P–V relationship of the arterial segment based on the pressure feedback. This is achieved by moving the piston of the compliance chamber, which is directly connected to the circulatory flow of the arterial segment and whose function forms the arterial waveform. The cascaded controller drives the piston quickly and converts the excess or drop in pressure into a volumetric shift until the reference pressure is reached. Physiological wave reflection in the native arterial circulation contributes both to aortic pressure waveforms and to ventricular‐vascular coupling.In contrast to the human vasculature, the negative slope of the P–V relationship in the compliance chamber results from the reversible expansion of the rigid chamber. To better understand the movement profile of the controller, the displacement profiles of each hemodynamic scenario are shown in Figure −3 s. On the other hand, the ACC responds via the cascaded controller, which has a current control cycle of up to 6.2 × 10−5 s for dynamic positioning , the latter has a much greater influence on the mechanical response of the tissue. It promotes an undesired sequence of events that result not only from the pressure‐load  but also from flow disturbances  that synergistically dysregulate the cross‐talk between endothelial and smooth muscle cells. Changes in phenotype therefore lead to arterial wall ramifications.Future studies could include stented aortas from human cadavers attached to the testing unit. This allows us to study the mechanical and structural properties of stented arteries under hemodynamical loading, for example at the proximal landing zone, where the stent interacts with the aortic wall and is known to be a prone area for endoleaks and vascular complications.The aim of this study is to present an MCL for long‐term tests of stented arteries and stent‐grafts from a biomechanical point of view and to validate the function of the active compliance chamber. The versatility of the design allows for a variety of hemodynamic scenarios to be reproduced and for different arteries to be tested, while the compliance chamber allows for different pressure waveforms to be simulated regardless of shape. Physiological shear and nominal stresses in the arterial wall are said to improve the cellular environment toward in vivo phenotype that prevents vascular remodeling/dysfunction. With controlled variable compliance, the MCL can be used to evaluate mechanical vascular grafts, stent‐grafts, and implants that are complementary to arteries that require a compliance gradient.5This is primarily a control paper and no arterial tissue is involved. The authors do not intend to imply that this MCL is superior to the above systems, but rather to suggest a different approach that is more beneficial for arterial testing. The limitations of this study include a systolic time‐shift of the reproduced LVP with respect to the mechanical setup. As an in vitro setup, it has a pressure feedback function with a closed control loop for the compliance chamber (purpose of the system) and other autoregulatory mechanisms of the human circulation are missing. In addition, the MCL lacks a Frank–Starling mechanism and a variable resistance. It should be noted that its current state is designed for testing arteries and stents and it cannot assist in the evaluation of cardiac devices and other related applications. Partial diastolic flow is also created, but the artery's innate flow storage during systolic expansion compensates for diastolic flow. The experimental setup presented cannot replace clinical or in vivo tests of arteries and stents, but serves as a preclinical evaluator to optimize stents and to provide insights into the reaction of the arterial tissue after implantation. Future studies should use variable peripheral resistance, ultrasonic flow measurement, and pressure sensors with higher accuracy.6The adaptability of the active compliance chamber in real‐time under different hemodynamic scenarios makes it an optimal compliance candidate for stress‐based artery testing. This is achieved by separating the ventricular and arterial segments using a control profile. The compliance chamber responds to the ventricular hemodynamics and modifies the arterial pressure waveform in order to maintain a certain compliance curve. This function enables the assessment of different stent‐grafts and arteries, whose own compliance profile varies. The presented MCL is a valuable tool for researching arteries and stent‐grafts in the biomechanical field. It can be used to test different stent‐grafts and arteries when realistic physiological conditions, loading scenarios, and a pressure gradient are required.The authors declare no conflict of interest.Emmanouil Agrafiotis, Markus A. Geith, Gerhard Sommer, Sotirios Spiliopoulos, Gerhard A. Holzapfel designed concept. Emmanouil Agrafiotis, Gerhard A. Holzapfel performed methodology. Mohammad A. Golkani was incharge of software. Emmanouil Agrafiotis performed data collection. Emmanouil Agrafiotis performed data analysis. Sotirios Spiliopoulos, Vera Hergesell, Gerhard A. Holzapfel were incharge of funding acquisition. Sotirios Spiliopoulos and Gerhard A. Holzapfel did supervision. Emmanouil Agrafiotis prepared manuscript. Gerhard Sommer, Sotirios Spiliopoulos, and Gerhard A. Holzapfel did critical revision of manuscript.


The test results show that: The optimal parameter combination was 45° between the straw deflector and the vertical direction, 200 mm height difference between straw deflector and outlet, 0° inclination angle of inner deflector and 35° inclination angle of outer deflector. The qualified rate of straw scattering was 72.2% in the corresponding simulation test, 93.6% in the bench test and 95.2% in the field test, which could meet the demand of first season harvest of ratoon rice.Since it is requested that the smashed straw should not be scattered onto the stubble in the first season harvest, a smashing and scattering device matched with the first season harvester of ratoon rice was designed in this paper to smash and scatter the straw into the rolling area. The main structural parameters affecting the straw scattering performance were determined by theoretical analysis of the deflecting performance of the straw deflector. EDEM software was used to simulate and analyze the straw scattering situation under the action of the deflector. Taking the qualified rate of straw scattering as the performance index, the optimal parameter combination of the straw deflector was determined by L It can make full use of temperature and light resources and save labor and seed. In addition, with high quality, the ratoon rice can help to increase both production and income6.Ratoon rice refers to the production of a second rice crop in one cropping season developed from regenerating rice tillers from nodal buds of the stubble that was left behind after the first seasonal rice harvest8. The yield of the first season is mainly determined by rice varieties, growth conditions  and cultivation and management measures, while the yield of the second season is determined by the harvest, growth conditions and management measures of the first season10. Agricultural studies show that during mechanized harvesting in the first season of ratooning rice, the paddy is wet and soft, and the rice stems are thick and green. In order to promote the sprouting of ear heads in the ratooning season, it is required to have high stubble retention, low rolling rate and light rolling degree, and strong threshing capacity of the roller to adapt to strong and wet materials. When the harvester is working, miscellaneous residues such as rice straw and leaves will be scattered into the paddy field. If the straw is smashed and scattered in disorder, they will remain on the upper part of the rice stubble, which will easily cause rice straw to rot and thus affect the germination of regenerated ear heads12. Therefore, the first season harvest of ratoon rice should make sure that the straw is smashed and scattered without covering the stubble.In order to increase the annual yield of ratoon rice, high yield in the first season of ratoon rice and full heading in the regenerating season are required14. There are few studies on harvesting technology of ratoon rice in the first season, and no corresponding straw processing techniques have been found. Scholars at home and abroad have carried out researches on increasing the rotational speed of the smashing tool shaft, improving the structure of the smashing tool, improving the air flow characteristics in the smashing chamber, improving the shape of the smashing chamber, installing the scattering regulating device and so on to increase the evenness of the straw scattering of the smashing and scattering returning machine.The harvest technology in the first season of ratoon rice is still bottleneck in the popularization and development of ratoon rice15 designed an adjustable straw smashing and scattering returning machine, whose qualified rate of smashed straw length could reach 90.01% and the unevenness of straw scattering was 22.95%. Sun et al.16 designed a differential saw-cutting rice straw smashing and returning machine. Its qualified rate of straw length could reach 93.23% and the unevenness of scattering was 20.89%. Qin et al.17 designed a straw smashing and scattering device for the straw returning fertilizing and sowing machine. Its qualified rate of straw length was 96.6%, the qualified rate of straw scattering range was 90.2%, and the unevenness of straw scattering was only 11.9%. The qualified rate of straw smashing length and the unevenness of straw scattering are both used as the performance indexes of the existing straw smashing and scattering devices matching with harvesters. Thakur et al.18 developed a smashing device matching with harvester, which achieved the best performance when the stem moisture content was 70%, machine tool working speed was 0.56 m/s and the knife roller speed was 1500 r/min. Schillinger et al.19 installed a high-pressure fan on the harvester to improve the scatter evenness of straw. However, although the fan could improve the evenness of the straw scattering after smashing, it would make the structure of the machine complex, and significantly increase the power consumption of the machine. The straw scatter width and evenness also become more difficult to control. Lisowski et al.20 used Fluent software to analyze the movement process of the straw at the outlet of the harvester cylinder, and studied the relationship between the speed of the smashing knife of the smashing device and the outlet speed of the threshing cylinder. These researches mainly took straw counters-field set or regular harvester as research objects, whose performance indexes such as average stubble height, qualified rate of crushing length, scattering unevenness, and scattering width were given priority to. Although these researches improved straw crushing effect and evenness of straw scattering, they did not meet the requirements of mechanized agricultural harvest of ratoon rice in the first season and could not effectively solve the problem of straw covering during the first harvest of ratoon rice, which directly affected the growth of regenerated buds in the second season.Zhang et al.To effectively solve the straw covering problem during harvest of ratoon rice in the first season, based on the double-channel feeding ratoon rice harvester independently developed by our team, we adopted the EDEM software to simulate the straw scattering process to obtain the optimal structural parameters of the straw deflector which can lead the crushed straw into the rolling area. At the same time, bench and field experiments were carried out to verify the feasibility of the design. This study can provide reference for the research and promotion of mechanized harvesting technology and equipment of ratoon rice in the middle and lower reaches of the Yangtze River.22, which is shown in Fig. The smashing and scattering device was fit on the feeding ratoon rice harvesterThe smashing and scattering device mainly consist of main box, straw deflector, knife roller, fix knife set and so on. The main box is connected by hinges to the outlet of the threshing and cleaning cylinder of the harvester, from which the straw is discharged. The side cover plate of the main box is provided with an anti-entangling ring, which is compatible with the anti-entangling end cover on the knife shaft of the moving knife roller to avoid the straw winding the knife shaft. There is an arc straw catching plate between the smashing and scattering device and the threshing and cleaning chamber. The straw falling on the arc straw catching plate is grabbed by the high-speed rotating knife roller and enters the box of the smashing and scattering device. Under the combined action of multiple groups of moving knives and fixed knives, the straw is smashed into fragmentized ones. Under the action of high-speed rotating centrifugal force of the knife roller, the smashed straw is thrown out along the tangent direction. Finally, under the action of flow diversion of the straw deflector, the smashed straw is thrown to the two crawler rolling areas respectively. The structure and working principle of smashed straw are shown in Fig. The working principle of the straw deflector is to change the motion state of the straw after colliding with the deflector under the external force which will change its initial position, angle, and velocity, allowing it continue to move by a new trajectory. The straw deflector consists of cover deflector, inner deflector, and outer deflector. The force states when the smashed straw collides with different deflector are similar. Taking the straw cover deflector as an example, the force at the moment when straw collides with the cover deflector was analyzed. The object was a piece of single smashed straw, which was regarded as a particle, and the influence of air flow on the straw was ignored.Take the smashed straw as the origin of the coordinate axis, the motion direction of the straw as the positive X-axis direction, and the opposite gravity direction as the positive Y-axis direction to establish the plane coordinate system as shown in Fig. vs = Instantaneous speed of the straw colliding with the deflector (m/s), ms = Mass of the smashed straw (kg), g = Gravitational acceleration (9.8 m/s2), αs0 = The angle between the direction of motion and the X axis when colliding with the deflector (°), αs1 = The angle between the direction of motion and the cover deflector when colliding with the deflector (°), αs2 = The angle between FH and negative Y-axis direction when the straw colliding with the deflector (°), αs3 = The angle between FH and NF when the straw colliding with the deflector (°), αs4 = The angle between the direction of motion and the FH when the straw colliding with the deflector (°).It can be obtained from the triangle similarity relation:It can be obtained by substituting Eq.  into Eq.It can be seen from Eq.  that wheLSC. Only part of the device is located directly above the track with a width of LSC1, corresponding to the space M inside the device; the rest part is located outside the track with a width of LSC2, corresponding to the space N inside the device.Figure Ignoring the air force and interaction between the straw, the straw is only subjected to air resistance and gravity. According to the agronomy requirements of the first season harvest of ratoon rice, the straw discharged from the harvester should not cover the rice stubble, that is, the ideal state is to scatter all the smashed straw to the rolling area. As shown in Fig. ζDC is the angle between the straw deflector and the vertical direction. The larger ζDC was, the farther the straw will be scattered. When ζDC ≥ 90°, the straw deflector loses its function of deflecting. Besides, the larger ζDC is, the larger the length of cover deflector SDC will be. When ζ = 0°, the smashed straw will collide with the vertical baffle and fall directly, so it could not be scattered backward and will easily get blocked in the chamber. In the Actual scattering process, due to the influence of air, the farther the scattering distance is, the farther the lateral movement of smashed straw will be, that is, the amount of smashed straw scattered outside the rolling area will increase. In order to explore the influence of ζDC on the qualified rate of the scattering, the ζDC test factors are set as 30°, 45° and 60° considering the length of the straw cover deflector SDC and the actual blockage.After installing the straw deflector, the scatter distance of smashed straw can be limited. As shown in Fig. hDC is the height difference between the tail of the straw deflector and the outlet. The smaller hDC is, the fewer smashed straw will collide with the straw deflector after flat, up, or down scattering. In order to explore the impact of hDC on the qualified rate of scattering, the factor levels were set as 0 mm, 100 mm, and 200 mm on the premise of not interfering with other mechanisms fully considering the structural relations between straw deflector and frame, grain bin, and chassis track.In Fig. Q’ S3, QS1 and QS3, and the stubble height is hLC. It can be seen the maximum height of the boundary between QS1 and QS3 should be avoided for the straw discharged from M and N zones to falling into the rolling area QS2. Therefore, it can be inferred according to the geometric relationship that the following conditions must be met for the inner and outer deflector to scatter the smashed straw into the rolling area rather than on the rice stubble:βz = inclination angle of inner deflector (°), βy = inclination angle of outer deflector (°).As shown in Fig. βz ∈ , βy ∈ . Therefore, the level of inclination factor of the inner deflector was set as − 10°, 0° and 10°, and the level of inclination factor of the outer deflector was set as 25°, 35° and 45°.It can be obtained from the whole machine and the structural parameters of the smashing chamber that 24. The simulated gravity acceleration was 9.81 m/s2, and the material of the smashing and scattering device was selected as Q235. The front of the smashing chamber may give the straw a wrong way out, so it was closed in the 3D model during simulation.Pro/E software was used to carry out three-dimensional modeling of the smashing and scattering device and imported it into the geometry module in EDEM softwareQS1, QS2, and QS3 in Fig. 25.As shown in Fig. 2 of straw falling into the area in continuous 3 s when the straw was scattered through the device. Then, square mass sensor I and square mass sensor III were set respectively, and the mass of straw scattered on the rice stubble in the two areas of the harvest area was marked as m1 and m3.A square mass sensor II with a width of 400 mm was set on the rolling area, which was used to calculate the accumulative mass mThe feeding amount of the double-channel feed ratoon rice harvester is 4.0 kg/s, 2.0 kg/s for a single channel. The straw fed into the smashing device was set to be 1 kg/s according to the ratio of grain and straw which is 1:1. During each simulation, the knife roller was set to rotate continuously with the speed of 2800 r/min, the total mass was set to be 3 kg, and 1 kg was generated per second. The total simulation time was set to 5 s to reduce the straw residue in the chamber. The particle generating plane was arranged above the arc straw catching plate, and the length and width of the rectangular plane were 496 mm and 150 mm respectively. According to the linear velocity of threshing cylinder, the particles were set to be − 21 m/s along Z axis.27.The straw material was approximately formed into a cylinder with a diameter of 4 mm and a length of about 80 mm to build the straw discrete element model of ratoon rice, as shown in Fig. 11, m2 and m3, the proportion of the straw falling into the smashing area ηFZ was calculated as:ηFZ = Qualified rate of scattered smashed straw in the simulation (%), m1 = Total mass of smashed straw in square sensor I (simulated stubble area QS1) (g), m2 = Total mass of smashed straw in square sensor II (simulated stubble area QS2) (g), m3 = Total mass of smashed straw in square sensor III (simulated stubble area QS3) (g).Since there will be straw residue in the smashing chamber during simulation, and a small amount of straw will fall outside the statistical area, the sum of the mass statistics in the three square sensors is taken as the total amount of straw. By counting the mass of the straw falling into the three square sensors mηFZ is used as a parameter to evaluate the performance of straw smashing and scattering device. The higher the value of ηFZ is, the better the performance is. Therefore, it is defined as the qualified rate of straw scattering. The scattering effect of straw under different structural parameters of straw deflector can be analyzed by ηFZ.In this simulation test, the angle between the cover deflector and the vertical direction A, the height difference between the tail of the cover deflector and the outlet B, the inclination angle of the inner deflector C and the inclination angle of the outer deflector D were selected as the test factors. According to the design and analysis of the parameters of the tail of the cover deflector, three levels of the four factors were selected for orthogonal test respectively, as shown in Table Interaction is an influencing factor to be considered in the process of orthogonal test design. The interactive discrimination tests between factors A and B, A and C, A and D, B and C, B and D, C and D were carried out respectively. Taking the discriminant method of interaction between factors A and B as an example, there were 9 combinations between factor A and B, keeping C and D unchanged. Taking the qualified rate of straw scattering as the index, each combination was tested once, and the same went for the other 5 groups.29. Finally, the interaction column was set up in the orthogonal table based on the interaction discriminant results and the header of the orthogonal test was designed.According to the generated interaction curve, if the three curves in each combination test have similar trends, it suggested there was no interaction between the two factors, or the interaction could be ignoredThe structure model of the straw deflector was constructed by the combination of the optimal structural parameters in the simulation test. The straw deflector was installed on the smashing and scattering device and fit with the double-channel feeding ratoon rice harvester.Fengliangyouxiang No. 1. The stubble height above 350 mm was manually harvested and transported to the test base. Then it was threshed for the test.The test material was first season ratoon rice at maturity, and the variety was S2; Stubble area QS3 was between the right boundary of header and the outside of right track; The stubble area QS1 is simulated between the inside of the left track and the inside of the right track, and the stubble height is 350 mm. The material was only fed from the header feeding inlet at the corresponding side of the test side of the straw smashing and scattering device. The reel was removed and the header was lifted to a height of 350 mm above the ground. To ensure safety, during the test, only the working clutch on the test side of the harvester was in the “on” state, the working parts on the other side were not started, and the working clutch was in the “off” state. Thus, only the two-way screw auger of the header rotated, and the cutter was stationary. The test site is shown in Fig. In order to make the test conditions close to the simulation test, the right side (rear view) straw scattering device of the double-channel feeding ratoon rice harvester was selected to install the straw deflector with the optimal parameters obtained from the simulation test. A 400 mm wide and 5000 mm long space is isolated behind the harvester track with color strip cloth to simulate the track rolling area QQS1, MQS2 and MQS3. The qualified rate ηQS of the straw was calculated. Repeat the test for 5 times to obtain the average value, then the solution formula of ηQS was:ηQS = Qualified rate of smashed straw scattering in the bench test (%), MQS1 = The total mass of smashed straw in simulated stubble area QS1 in the bench test (g), MQS2 = The total mass of smashed straw in simulated stubble area QS2 in the bench test (g), MQS3 = The total mass of smashed straw in simulated stubble area QS3 in the bench test (g).During the test, 1 kg material was fed from the feeding inlet of the header every second for 3 consecutive times, and the harvester was stopped when the smashing and scattering device stopped scattering the smashed straw at the test side. The straw in three areas behind the tracks was collected. Remove the impurities and weigh the rest MFengliangyouxiang 1, and the field test site is shown in Fig. To further verify the rationality of simulation test and bench test, the smashing and scattering field performance test of the straw smashing and scattering device, which was installed on the double-channel feeding harvester for ratoon rice, was carried out in the rice demonstration base of Si Wu Men Village, Wulin Town, Honghu City, Hubei Province on August 10th, 2020. The ratoon rice variety is Conservation tillage equipment-Smashed straw machine (GB/T 24675.6-2009)30 and the qualified rate of scattering was taken as the test index.Field test was carried out on the scattering performance of the smashing and scattering device based on MSP1; Collect all the straw in the un-rolling stubble area, including all the straw fragments covering the stubble and falling to the ground between the stubble, remove the impurity, weigh, and record as MSP2. The qualified rate ηPS of field integrated scattering can be calculated as:The double-channel feeding ratoon rice harvester operated at a speed of 0.8 m/s testing two strokes. Select 3 points at equal intervals in the two strokes for measurement, and a total of 6 points were tested. Each point was an area with a length of 6 m  and a width of 1 m in two adjacent operation strokes. Collect all the straw in the 4 rolling rows in the area, remove the impurity, weight, and record as ηPS = Qualified rate of integrated scattering in the field (%), MSP1 = The mass of the straw in the rolling area (g), MSP2 = The mass of the straw in the stubble area (g).Where Human ethics was not required for this study since human were only the operators of the machines rather than the subjects of the test. The collected plant materials and research activities were in accordance with the laws and regulations of Hubei Province, China. The collection of ratoon rice straw materials had been approved by the paddy field owner of Chunlu Specialized Cooperative in Honghu, Hubei, China. All participants gave informed consent prior to participation.Figure 27 (313) orthogonal table is selected for this test for 8 factors with 3 levels.There is interaction between factors A and D, C and D in the structural parameters of straw deflector, so the interaction column is set in the orthogonal table. The interaction between any 2 factors with 3 levels occupies two columns, so L27 (313) header, and the simulation test results were obtained for 27 times, as shown in Table ηFZ is, the better the scattering effect was. Therefore, the order of primary and secondary factors affecting the scattering performance is B, D, C, A × D, C × D, A.Orthogonal test was carried out with L27 13 headerMSA < MSe, factor A belongs to the error term, and the corrected difference source e was obtained. The results of variance analysis of orthogonal test are shown in Table In order to explore the importance of the influence of the four structural parameters of the straw deflector on scattering performance, combined with the interaction between the factors, the variance analysis was carried out on the simulation test results. In variance analysis, since 2B3C2D2, that is, the included angle between the cover straw deflector and the vertical direction was 45°, the height difference between the tail of the cover straw deflector and the outlet was 200 mm, the inclination angle of the inner deflector was 0°, and the inclination angle of the outer deflector was 35°.B and D have remarkable significant influence on the test results; Factors C and A × D have significant influence on the test results, but interaction A × D has less influence on the test results than B, D and C. Factors A and C × D had no significant effect on the test results. Therefore, the interaction can be ignored when determining the optimal level of the four factors. The optimal scheme was A2B3C2D2 was analyzed. Figure S1 and QS3, and the straw falling into these two areas were very close to the simulation baffle II and baffle III, indicating that the displacement (Y direction) of the straw under the guidance of the inner and outer deflector was small, and the scattering range was concentrated. It can be seen from Y direction and Z direction view that a small amount of straw fell near the outlet due to the small initial velocity or falling during the rotation of the knife roller. However, the triangular blank area formed by the outer deflector and the X axis direction was not covered by the bottom plate, so the amount of straw in the QS3 area was greater than that in the QS1 area. In the Y direction view, the scattering distance (displacement in the X direction) of the smashed straw was short. After the smashed straw being discharged from the outlet, they were blocked by the cover deflector and changed the velocity direction. Then, the smashed straw fell to the ground within the angle between the cover straw deflector and the vertical direction. Figure S1, QS2 and QS3 was 314.427 g, 1890.04 g and 412.605 g, respectively, and the proportion of straw falling into QS2 was 72.2%. The total amount of straw in the three areas was 2617.072 g, and the total amount of straw generated by the simulation was 3000 g. This was because there were still straw residues in the straw scattering room after the simulation, which was consistent with the actual working condition of the smashing and scattering device.The straw scattering process under scheme AS3, and there was no straw in the left stubble area QS1. Most of the straw was scattered to the rolling area QS2. The straw in each area was collected and weighed to obtain the test data as shown in Table Figure In the simulation test, the material properties of the established straw particles were fixed, the discrete degree of straw particles was not normal distribution in a complete sense, and there were differences in the material properties among individual straw of ratoon rice in the field harvest progress.In the simulation, only the straw model was established. However, the smashing and scattering device dealt not only the straw, but also with leaves, ear heads and branches, etc. during field harvest. Although these parts did not account for a large amount, they would indeed affect the collision between the smashed particles, and then affect scattering performance.In fact, the straw of ratoon rice is flexible. After being broken, the flexible straw was intertwined with each other and polymerized, and there would be many clumps of smashed straw, whose properties changed greatly, and the force exerted on them was very different from that of a single one.S3 were all straw fragments that were thoroughly smashed. These fragments were not intertwined before, and were scattered into the area under the action of wind generated by the rotation of the knifer roller and the sweep gas from the harvester engine exhaust pipe. And this straw can fall from the rice stubble to the ground in the actual field harvest, which will cover the rice stubble.It was observed that the straw scattered into the right simulated stubble area QAccording to the results of the bench test, the qualified rate of the straw scattering reached 93.6%, while the optimal qualified rate of the simulation test was 72.2%, and the deviation was 21.4%. The main reasons for the deviation are as follows:Figure Based on the agrological requirement that the straw of ratoon rice should be smashed and scattered without covering the stubble in the first season harvest, a straw smashing and scattering device matching with the straw scattering requirements of the double-channel feeding ratoon rice harvester was designed in this paper, which could smash the straw from the threshing cylinder and scatter it into the required rolling area.According to the kinematic theory, the force on the straw at the moment when the straw collides with the straw deflector was analyzed. It was found that the angle and size of the straw deflector had a great impact on the straw scattering performance. According to the spatial position relationship between the straw scattering device and the crawler of the double-channel feeding ratoon rice harvester, it was determined that the included angle between the straw deflector and the vertical direction, the height difference between the rear of the straw deflector and the straw outlet, the inclination of the inner plate and the outer plate were the main factors affecting the straw scattering performance.27 (313), the optimal combination of parameters was obtained as follows: the angle between the cover deflector and the vertical direction was 45°, the height difference between the tail of the cover deflector and the outlet was 200 mm, the inclination angle of the inner deflector was 0°, and the inclination angle of the outer deflector was 35°. The qualified rate of scattering simulation was 72.2%.The situation of straw scattering under the action of straw deflector was simulated and analyzed by using EDEM software. It was found that there is a certain interaction between the angle between the straw deflector and the vertical direction and the inclination of the outer plate, the inclination of the inner plate and the inclination of the outer plate, and there was no obvious interaction between other factors. According to the orthogonal test of LAccording to the optimal combination of structural parameters obtained from the simulated orthogonal test, the qualified rate of the straw scattering reached 93.6% in the bench test, and the qualified rate of the comprehensive straw scattering reached 95.2% in the field test when it was fit with the double-channel feeding ratoon rice harvester, which could meet the harvest demand of the first season of ratoon rice. The smashed straw could basically be discharged to the two crawler rolling areas of the harvester to meet the harvest requirement of ratoon rice in the first season and facilitate the ear germination of ratoon rice in the second season.It can be seen from the results of the three groups of tests that although there was a big difference between the results of the simulation test and the bench test, the optimal parameter combination of the straw deflector selected by the simulation test did have a remarkable performance. Therefore, it is feasible to use EDEM software to simulate the process of straw scattering to study the influence of structural parameters of straw deflector on the performance of straw scattering.


Lithospheric net rotation (LNR) is the movement of the lithosphere as a solid body with respect to the mantle. Separating the signal of LNR from plate tectonic motion is therefore an important factor in producing absolute plate motion models. Net rotation is difficult to constrain because of uncertainties in geological data and outstanding questions about the stability of the mantle plumes used as a reference frame. We use mantle convection simulations to investigate the controlling factors for the magnitude of LNR and to find the statistical predictability of LNR in a fully self‐consistent convective system. We find that high lateral viscosity variations are required to produce Earth‐like values of LNR. When the temperature dependence of viscosity is lower, and therefore slabs are softer, other factors such as the presence of continents and a viscosity gradient at the transition zone are also important for determining the magnitude of net rotation. We find that, as an emergent property of the chaotic mantle convection system, the evolution of LNR is too complicated to predict in our models. However, we find that the range of LNR within the simulations follows a Gaussian distribution, with a correlation time of 5 Myr. The LNR from the models needs to be sampled for around 50 Myr to produce a fully Gaussian distribution. This implies, that within the time frames considered for absolute plate motion reconstructions, LNR can be treated as a Gaussian variable. This provides a new geodynamic constraint for absolute plate motion reconstructions. Net rotation is an emergent property of a chaotic system and is difficult to predict, but the range and distribution can be constrainedLarge lateral viscosity contrasts are required for an Earth‐like magnitude of net rotation in geodynamic modelsNet rotation follows a Gaussian distribution over timescales greater than 50 Myr with a correlation time of 5 Myr Net rotation is the movement of the entire lithosphere as a solid body with respect to the Earth's mantle. It is therefore one component of the motion recorded with respect to the Earth's magnetic dipole, preserved in the palaeomagnetism of rocks. However, three other components of motion are also preserved in the palaeomagnetism Jurdy, : movemenThe lithospheric net rotation (LNR) estimates require a stable reference point in the mantle. Mantle plumes and hotspots are generally used, as these are considered to have been roughly stable for the last few tens of millions of years  and they develop self‐organizing plate tectonics with spreading ridges and subduction zones. In agreement with previous studies, we find that changing the viscosity, especially the parameters that increase the lateral variation of viscosity, increases the magnitude of lithospheric net rotation. For models with highly temperature‐dependent viscosity and therefore stiff slabs, we achieve ranges of LNR within the published ranges for Earth. Our large viscosity contrasts mean that changing the presence and thickness of continents makes little difference to LNR, because the presence of stiff slabs in the mantle creates a much greater viscosity contrast than the continents, in contrast to previous studies.21.6×106 Lagrangian tracers. The surface and core‐mantle boundaries both have free‐slip conditions. Where present, two continents are initialized to cover 30% of the surface. They are stiffer and more buoyant than the upper mantle and lithosphere to ensure that they remain at the surface. They have lower yield stress margins, allowing them to form a single supercontinent and subsequently break up. The mantle is initialized with a layer of denser primordial material at the core‐mantle boundary. There is internal heating, but this does not decay with time. We, therefore run the models until they reach a stable whole mantle mean temperature, at which point we judge them to have entered a statistically stable convective state. Once the models have reached a statistical steady state, we run them for at least a further 600 time steps. We use this stable phase of the run for all of our subsequent analyses.Our convection models are incompressible and were run using the geodynamical code StagYY with a 2D spherical annulus geometry  of 106, where:α0 is the surface thermal expansivity, ρ0 is reference density, g gravitational acceleration, ΔT is the difference in temperature between top and bottom, D is mantle thickness, ηref is reference viscosity and κ0 is thermal diffusivity.We use a Rayleigh number (Ea) and viscosity activation volume (Va) determine the response of viscosity, η, to pressure and temperature:P is pressure, R is the gas constant and T is temperature. η0 is a scaling prefactor used to obtain a volumetrically averaged viscosity equal to ηref for an isothermal mantle of potential temperature 0.64 in dimensionless units. After running a calculation, the maximum viscosity is at the surface and the minimum in most cases in the modeled asthenosphere where the temperature is close to 0.75 in dimensionless units. In some models, we include a viscosity jump between the upper and lower mantle by a factor of 30. Viscosity is restricted to between a non‐dimensional range of 10−6–104. We use an oceanic yield stress to determine the strength of the lithosphere of between 2 ×102 and 2 ×106, although the majority of simulations have yield stress 2 ×104. The basal temperature, which models heating from the core, has a constant non‐dimensional value of 1.12. We also change the internal mantle heating rate. Equivalent dimensional values are given in Table We investigate the effects of eight parameters on lithospheric net rotation Table . Details1×108 and viscosity factor 10 at the outside, increasing to 1×1014 and viscosity factor 1,000 at the center. Some models have no continents.The initial layer of dense primordial material at the base of the mantle changes in thickness and viscosity between models, as does the thickness of the buoyant, stiff continents. The continents have a weaker rim to allow them to rift, with a yield stress of The spherical annulus geometry we use was developed by Hernlund and Tackley , which rω for each azimuthal and radial element, θ and r, in the model:Vθr, summed over θ and r and divided by total volume V, to give the total mantle net rotation. We then remove that component of the velocity field, leaving the kinematic information about net rotation.In order to solve the Navier‐Stokes equations, it is necessary to define a reference frame for velocity. There are different ways to define the reference frame. StagYY uses a no surface net rotation reference frame to calculate the velocity at each point. Technically speaking, a numerical solution is obtained in an arbitrary reference frame, and a global solid rotation is imposed to move this solution back to the no surface net rotation reference frame. We then post‐process the models to find surface velocity and rotation in a no mean mantle net rotation frame, in a similar way to Zhong . To tran33.1Ea . This result is in line with the results of previous studies , makes very little difference to LNR at any Ea. Previous studies found that both the presence and thickness of continents  and continents. The maximum LNR is 0.184°/Myr, although for most of its life the LNR does not exceed 0.05°/Myr. Figure The majority of models do not have supercontinent cycles. The continents converge during the pre‐stabilization phase before analysis starts and do not subsequently diverge. In these models, there is no clear link between geodynamic processes and LNR. We present model 12 .Each set of 1D correlation profiles are stacked according to the convection properties of the models, with increasing values of 3.3.2Ea and Va both increase the positive correlation in the mid‐mantle. These parameters enhance the viscosity contrast of slabs, highlighting that at times when there are more slabs in the mid‐mantle, net rotation is often stronger. The effects of a fast‐moving asthenosphere are not visible in the viscosity correlation. This is because the sensitivity of viscosity to temperature is somewhat lower at lower pressures. The correlation is also stronger in simulations without a viscosity jump, because these have higher upper mantle viscosity. We also consider the viscosity profile below the oceans and continents separately. Where present, the continents cover 30% of the surface. The sub‐oceanic mantle makes up the majority and it is therefore unsurprising that the sub‐oceanic correlations are more similar to the global viscosity correlations. The sub‐continental mantle shows very little correlation with NR in any simulation, although we do see a slight increase in correlation immediately below the continents (depth 0.096) in some simulations. This is again related to surface mobility ‐ stationary continents insulate the upper mantle, reducing viscosity. More mobile continents move over colder areas and so will have slightly higher subcontinental viscosity, which correlates with higher mobility and net rotation. The positive mid‐mantle correlations in high Ea and Va cases continues for sub‐oceanic profiles. Most slabs are subducted in sub‐oceanic mantle so this is to be expected. The effects of the continents can be seen with an increase in correlation strength at a depth of 0.096. Above this depth, the contribution of continents limits the correlation between viscosity and LNR.The strength of the correlation between the 1D viscosity profile and LNR is very clearly a function of the viscosity parameters chosen. Increasing Whilst there is no clear pattern linking thermal or tectonic structure to LNR, we can at least investigate over what time scales LNR is stable. Figure DKL) divergence between the chunk distribution and a Gaussian distribution. If the distribution of LNR with the chunk is Gaussian, the KL divergence will be zero. The KL divergence is calculated by:P(x) and Q(x) are the normalised probability of LNR taking value x in the chunk and a Gaussian distribution respectively. The DKL never reaches 0 because the chunks are too short, so the distribution is imperfectly sampled. However, depending on the model parameters, most models have average DKL over all chunks approaching zero by the time the chunks have length 50 Myr, and within 25 Myr in many cases.We also investigate over what timescales we need to sample net rotation in order to produce a Gaussian distribution. This is an important consideration because it determines over what timescales we can reasonably use a Gaussian distribution to model LNR. In order to do this, we separate the LNR for the whole model into chunks of set length. We repeat the exercise, with chunk lengths between 10 samples up to 1,000 samples. We then normalize the LNR in each chunk. If the distribution within the chunk is Gaussian, the normalized chunk distribution will be Gaussian. To test this, we use the Kullback‐Leibler , we may be able to use statistical methods, such as machine learning tools, to find characteristics of mantle flow that can determine the magnitude of LNR , where we get values comparable to Earth . Beyond this, the distribution of values of LNR is Gaussian, especially if time scales longer than 50 Myr are considered. This provides a new geodynamic constraint on the range of amplitudes and correlation periods expected for Earth, which can be used to constrain future absolute plate motion models.