Low Inflation Pressure Research Articles

Corrugated V-fold soft actuator with large deformation and high force density

Soft pneumatic actuators with a corrugated structure have the advantage of low inflation pressure and a large actuation range and have great potential for use in grippers. However, they are generally difficult to have both large deformation and high force density performance. Inspired by the hydraulic joints of spider legs, this paper designs a multi-cavity soft-pneumatic actuator with a corrugated V-fold structure, which realizes bending through the deformation of the air cavity structure instead of the traditional way of squeezing the air cavities against each other, and has significantly large curvature high force density compared with actuators such as PneuNets. At an inflation pressure of 40 kPa, the proposed soft actuator achieves a bending angle of 306° with a curvature of 0.114 rad mm−1, while at an inflation pressure of 45 kPa, the actuator achieves an actuation force of 5.15 N with a force density of 0.0101 mN (mm3.kPa)−1. The modeling approach based on continuum mechanics modeling of soft materials combined with finite element analysis (FEA) (or experiment) is proposed to achieve accurate modeling of the bending angle and actuation force of actuators with complex corrugated structures. In addition, the proposed actuator has made initial explorations into the application of soft grippers and has achieved fairly good gripping results compared to other types of grippers.

An economic appraisal of the effect of tire inflation pressure for alternative tillage systems on a silty clay loam soil

AbstractCompacting soil has an adverse effect on soil properties, decreases crop productivity, and subsequently reduces farm income. Low tire inflation pressure (LTP) help in managing soil compaction and protecting the soil environment; however, there is scant economic data available on LTP in US Midwest farming systems. Hence, a 3‐year study investigated the effects of LTP, compared to tires inflated to the standard tire inflation pressure systems, on crop yield and farm economy for a typical maize/soybean rotation. The effect of the two tire inflation pressure systems was factorialized with three tillage systems: deep tillage (DT, 450 mm), shallow tillage (ST, 100 mm), and no‐till systems. The results showed that LTP systems increased maize (Zea mays) yield by 4.51% (2017) and 2.70% (2018) and soybean (Glycine max) by 3.70% in 2018. Annual earnings for both 200‐ and 800‐ha farms increased for all tillage systems with LTP tires based on a partial budget analysis. The payback periods for LTP tires were very short, ranging from 0.32 years for DT on an 800‐ha farm to 1.18 years for ST on a 200‐ha farm. The net present value of the higher returns with LTP tires was substantial, especially for the DT system. This study shows a strong economic benefit from investments in LTP tires on silty clay loam soils in the US Midwest.

Measurement and Analysis of the Influence Factors of Tractor Tire Contact Area Based on a Multiple Linear Regression Equation

Tractor tire three-dimensional (3D) contact area is one of the significant concerns of the soil-tire coupling mechanism, and it influence soil compaction and the sustainable development of agriculture. In this study, we developed a method to measure the 3D contact area of a pneumatic tire using a laser profiler on a signal tire soil-bin testing facility. A 6.00-14 bias-ply tire with high lugs was driven on sandy loam soil in a soil-bin testing facility under different vertical loads, driving speeds, and inflation pressures. Then, we developed a multiple linear regression equation between the influence factors and tractor tire contact area. The results indicated that the contact area was impacted by the three factors involved in this study, and the inflation pressure significantly influenced results, and the combination of high speed (3 m/s), low inflation pressure (69 kPa), and high tire load (2.5 kN) led to a relatively high contact area on the soil-tire contact interface and possible severe soil compaction. Also, we found that the contact area varied in a quadratic manner with speed at a given inflation pressure and tire load and varied in a quadratic manner with inflation pressure at a given speed and tire load and varied linearly with the tire load for a given speed and inflation pressure.

Ischemic post-conditioning in acute ischemic stroke thrombectomy: A phase-I duration escalation study.

Previous experimental studies have found that ischemic post-conditioning exhibits neuroprotective effects by alleviating ischemia-reperfusion injury in an acute ischemic stroke model, and its efficacy is thought to be related to the duration of ischemic post-conditioning. However, ischemic post-conditioning has not been used in patients with acute ischemic stroke. This study aims to determine the safety, tolerability, and maximum tolerable duration of ischemic post-conditioning in patients with acute ischemic stroke receiving mechanical thrombectomy. Patients with acute ischemic stroke with unilateral middle cerebral artery M1 segment occlusion eligible for mechanical thrombectomy will be enrolled. We adopt a 3 + 3 dose-escalation design with a duration escalation schedule of 0, 1, 2, 3, 4, and 5 min × 4 cycles for the ischemic post-conditioning study. After successful reperfusion following mechanical thrombectomy, the balloon for ischemic post-conditioning will be inflated at the site proximal to the culprit lesion four times for 0-5 min with low-pressure (3-4 atmospheres) inflations, each separated by 0-5 min of reflow. We pre-defined the major responses (vessel perforation or rupture, reocclusion of the culprit vessel after ischemic post-conditioning, vessel dissection, severe vasospasm, ischemic post-conditioning related thrombotic events, and rupture of the balloon used for ischemic post-conditioning) as the stopping rules. Each patient will undergo a rigorous evaluation to determine the safety, tolerability, and maximum tolerable duration of ischemic post-conditioning. This will be the first clinical study to ascertain the safety and tolerability of ischemic post-conditioning in patients with acute ischemic stroke receiving mechanical thrombectomy. The maximum tolerable duration obtained in this study will also serve as a starting point for future studies on the efficacy of ischemic post-conditioning. [https://clinicaltrials.gov], identifier [NCT05153655].

The effects of traffic management systems on the yield and economics of crops grown in deep, shallow and zero tilled sandy loam soil over eight years.

This paper reports on a 3 × 3 factorial study to consider the effects of controlled traffic (CTF), low tyre inflation pressure (high flexion) tyres (LTP) and standard tyre inflation pressure (STP) farming systems for deep, shallow and zero tillage practices on the yield of wheat, barley, oats and field beans grown in a sandy loam soil in the UK. The main effect of tillage showed that the zero tillage option significantly (***P < 0.001) reduced crop yields in four out of the five of the first crop years, with no significant effect in years two, six and eight and exceeded the yield of the other tillage treatments in year seven. The specific costs of the alternative tillage systems were estimated, from which the cost saving for zero tillage compared to deep tillage was c. £ 60 ha−1 (US$ 80 ha−1), which compensated for the overall loss in yield. There were no significant differences between the crop yields from the deep and shallow tillage treatments, with shallow tillage offering savings in operational costs of c. £ 30 ha−1 (US$ 40 ha−1). Overall, the controlled traffic farming system, where 30% of the field was trafficked, produced 4% greater crop yields (*P < 0.05), worth £ 39 ha−1 (US$ 53 ha−1) than standard tyre inflation pressures (STP). The estimated effect of reducing the trafficked area to 15% resulted in a further 3% increase in mean yield with a corresponding total increase in crop value of 7% worth £ 74 ha−1 (US$ 100 ha−1) compared to the STP system. The beneficial effect of low inflation pressure tyres (70 kPa and 80 kPa) on crop yields, for the deep tillage treatment, was significantly greater (*P < 0.05) than those of the standard tyre pressure system (100 kPa to 150 kPa) returning an average 3.9% additional crop yield over the period of the experiment worth £ 39 ha−1 (US$ 53 ha−1).

Slurry Spreading on a Silt Loam Soil: Influence of Tyre Inflation Pressure, Number of Passages, Machinery Choice and Tillage Method on Physical Soil Quality and Sugar Beet Growth

Soil compaction forms a major threat to the well-functioning of agricultural soils. This threat is primarily driven by the increasing wheel loads of modern farming machinery and the increased frequency of field operations in periods when the soil is moist to wet and thus more prone to compaction. The application of slurry in early spring can have a highly detrimental impact, certainly for a crop like sugar beet, which is sensitive to soil compaction. A one-year experiment was set up on silt loam soil in the Belgian loess belt to assess the short-term impact of this field operation on soil under conventional ploughing and under non-inversion tillage. Two types of farming machinery were compared: a widely used tractor-trailer combination and a less common self-propelled slurry spreader, with the latter having higher wheel loads. Both machines were operated according to common or standard practice and a practice that aims at preventing soil compaction. For the tractor-trailer, this was with tyre inflation pressure recommended for road traffic and field traffic, respectively, corresponding with high and low tyre inflation pressure. The self-propelled slurry spreader was operated under standard and crab steering, respectively. Lowering the tyre inflation pressure to the recommended level for field traffic limited soil compaction and sugar beet yield loss. Although the effects of crab steering were less pronounced, it lowered the impact on the soil by limiting the number of passages. The overall machinery effect remained limited. The heavier self-propelled slurry spreader did not significantly increase the level of soil compactness and reduce sugar beet yield compared to the more common tractor-trailer combination. Soil under conventional ploughing showed more soil compaction, while the effectiveness of reducing tyre inflation pressure as a prevention strategy was lower compared to non-inversion tillage. The tillage practice, however, did not have any overall influence on sugar beet yield.

Extending the tire dynamic model range of operating conditions based on finite element method

Tire dynamics model is the basis of vehicle dynamic performance research, however, due to the limitation of safety and environmental conditions, the six-component physical test can not fully characterize the dynamic mechanical response characteristics of tire under special conditions such as low service inflation pressure, high load, and large range of operation temperature. To accurately describe the dynamic response of the tire under special operating conditions with the magic formula (MF) tire model, this paper combines the nonlinear finite element analysis and the experimental test. The finite element model of the tire is verified by the dynamic characteristic experiments, and the tire dynamics simulation under special operating conditions are also conducted based on the verification results. The MF tire model is modified and the parameter identification is performed for the prediction results to extend the operating conditions of the tire dynamic model. The results of the comparison show that the method proposed in this paper can realize the condition expansion of MF tire model under special conditions.

Clariant begins construction of flame retardants production facility in China

The goal of debulking strategies in endovascular interventions for peripheral arterial disease is to achieve a more uniform angioplasty result through plaque removal or plaque modification. This minimizes vessel wall barotrauma and maximizes acute luminal gain at lower inflation pressures. Improvement in drug delivery and reduced risk of restenosis with the use of a debulking strategy prior to the drug coated balloon (DCB) is hypothesized as an added benefit. However, the long-term benefits of atherectomy remain unclear with some studies suggesting worse outcomes with atherectomy. There are a plethora of debulking devices available to treat calcified peripheral arterial disease which will be reviewed in this book chapter.

Remote Ischaemic Conditioning in STEMI Patients in Sub-Saharan AFRICA: Rationale and Study Design for the RIC-AFRICA Trial

PurposeDespite evidence of myocardial infarct size reduction in animal studies, remote ischaemic conditioning (RIC) failed to improve clinical outcomes in the large CONDI-2/ERIC-PPCI trial. Potential reasons include that the predominantly low-risk study participants all received timely optimal reperfusion therapy by primary percutaneous coronary intervention (PPCI). Whether RIC can improve clinical outcomes in higher-risk STEMI patients in environments with poor access to early reperfusion or PPCI will be investigated in the RIC-AFRICA trial.MethodsThe RIC-AFRICA study is a sub-Saharan African multi-centre, randomized, double-blind, sham-controlled clinical trial designed to test the impact of RIC on the composite endpoint of 30-day mortality and heart failure in 1200 adult STEMI patients without access to PPCI. Randomized participants will be stratified by whether or not they receive thrombolytic therapy within 12 h or arrive outside the thrombolytic window (12–24 h). Participants will receive either RIC (four 5-min cycles of inflation [20 mmHg above systolic blood pressure] and deflation of an automated blood pressure cuff placed on the upper arm) or sham control (similar protocol but with low-pressure inflation of 20 mmHg and deflation) within 1 h of thrombolysis and applied daily for the next 2 days. STEMI patients arriving greater than 24 h after chest pain but within 72 h will be recruited to participate in a concurrently running independent observational arm.ConclusionThe RIC-AFRICA trial will determine whether RIC can reduce rates of death and heart failure in higher-risk sub-optimally reperfused STEMI patients, thereby providing a low-cost, non-invasive therapy for improving health outcomes.

Effect of Cover Crop, Slurry Application with Different Loads and Tire Inflation Pressures on Tire Track Depth, Soil Penetration Resistance and Maize Yield

Agricultural soils can be affected in their ecological functions by in-field traffic of agricultural machinery. A three-factorial research design was carried out in a field experiment to test the effect of slurry tanker filling level (filled, half-filled, empty), tire inflation pressure of the slurry tanker (high: 300 kPa, low: 100 kPa), and ground covering (+cover crop, −cover crop) on tire track and soil penetration resistance (averaged, 0–20 cm, 21–40 cm) after application on the fields in spring. Additionally, the effect on grain yield of the subsequent culture was considered. The total weight of the tractor slurry tanker combination was 16,470 kg (empty), 25,940 kg (half-filled), and 34,620 kg (filled). The low tire inflation pressure of the slurry tanker increased the mean tire–soil contact area by 75% (filled), 38% (half-filled), and 16% (empty tanker). The results obtained show a significant effect of tire inflation pressure and ground covering on the measured parameters. The tire inflation pressure reduction effect on track depth was highest in the filled slurry tanker (−17.8%). With increasing wheel load, the effect of reduced tire inflation pressure on soil penetration resistance (0–20 cm) increased. In the subsoil (21–40 cm), the effect of tire inflation pressure was much lower, indicating that a reduction of tire inflation pressure preserves the upper layers rather than the lower ones. Furthermore, cover crops are linked to a higher degree of soil deformation after traffic with the tractor–slurry combination due to their loosening effect on the topsoil. Tire tracks were 15.0% deeper in the cover crop field than in the field without a cover crop. It is assumed that cover crop mixtures with different types of root mass can influence the mitigation of soil compaction in an ameliorative way.

BROMINATED ISOBUTYLENE-CO-PARAMETHYLSTYRENE WITH SUPERIOR IMPERMEABILITY FOR TIRE INNERLINER APPLICATIONS

ABSTRACT Isobutylene elastomers are of great commercial importance in tire applications because of their notable low gas permeability properties, owing to their efficient molecular packing. Brominated isobutylene-co-para-methylstyrene (BIMSM) elastomers are a special class of isobutylene elastomers synthesized by random cationic polymerization of isobutylene and para-methylstyrene (pMS), followed by a selective bromination of the methyl group of the pMS units. BIMSM elastomer, commercially known as Exxpro™ specialty elastomer, exhibits superior heat resistance and aging properties and is much more resistant to chemicals and ozone than butyl- or halobutyl polymers because of its fully saturated backbone structure. The permeability properties of BIMSM elastomers can be tuned by the level of pMS comonomer present in the polymer chain. The pMS comonomer increases the glass transition temperature of the copolymer, and polymers with very low gas permeability needed for demanding tire air retention applications can be produced by suitably selecting the pMS content. A single type of benzylic bromide, but with a versatile functional group, allows for precise control of vulcanization chemistry, potential for other chemical transformations to achieve other reactive groups, and grafting reactions. We present the new material developments to meet the growing market demands and requirements for low maintenance, low inflation pressure loss rate tires and tires for connected autonomous shared electric vehicles.

A retrospective cohort study comparing high and low balloon inflation pressure on technical success and patency for treating central venous lesions in patients on chronic hemodialysis

Background We aimed to analyze the success rates and the access patency rates at 12 months between patients on chronic hemodialysis with symptomatic central venous stenosis (CVS) or occlusion (CVO), receiving high or low balloon inflation pressure for treatment. Methods We performed a retrospective study in which angioplasty balloons were inflated using a low-pressure or a high-pressure for the management of hemodialysis patients with CVS/CVO. The outcomes of this study were the success rate and the access patency rates at 12 months after balloon angioplasty, and the differences between groups were compared. Results We included a total of 74 patients on hemodialysis and assigned them to the low-pressure or the high-pressure groups. Success rates in patients of the high-pressure group (94.12%) were higher than those in patients of the low-pressure group (67.50%) (p = 0.005). With a total of 59 patients with technical success, at 6 and 12 months after angioplasty, the rates of access patency in the low-pressure group were 68 and 48%, respectively; on the other hand, the primary patency rates in the high-pressure group were 86.67% (6-months) and 76.67% (12-months). The 6 and 12 months post-interventional patency rates were higher in patients of the high-pressure group than those in patients of the low-pressure group (p = 0.10 at 6 months and p = 0.03 at 12 months). Conclusions Compared to balloon angioplasty using a low inflation pressure, hemodialysis patients with CVS/CVO receiving angioplasty using a high inflation pressure have significantly higher technical success and 12-month patency rates.

Efficacy of Low-Pressure Inflation of Oversized Drug-Coated Balloon for Coronary Artery Disease.

Objectives This study sought to assess the efficacy of oversized drug-coated balloon (DCB) inflation at low pressure for the prevention of acute dissections and late restenosis. Background The major limitation of DCB coronary angioplasty is the occurrence of severe dissection after inflation of DCB. Methods Between 2014 and 2018, 273 consecutive patients were retrospectively studied. 191 lesions (154 patients) treated by oversized DCB inflation at low pressure (<4 atm, 2.4 ± 1.2 atm, DCB/artery ratio 1.14 ± 0.22; LP group) were compared with 135 lesions (119 patients) treated by the standard DCB technique (7.1 ± 2.2 atm, DCB/artery ratio 1.03 ± 0.16; SP group). Results Although the lesions in the LP group were more complex than those in the SP group (smaller reference diameter (2.38 mm vs. 2.57 mm, P=0.011), longer lesions (11.7 mm vs. 10.5 mm, P=0.10), and more frequent use of rotational atherectomy (45.0% vs. 28.1%, P=0.003), there was no significant difference in the NHLBI type of dissections between the two groups (11.5%, 12.0%, 5.2% vs. 12.6%, 12.6%, 2.2% in type A, B, and C, P=0.61), and no bailout stenting was required. In 125 well-matched lesion pairs after propensity score analysis, the cumulative incidence of target lesion revascularization at 3 years was 4.5% vs. 7.0%, respectively (P=0.60). Late lumen loss (−0.00 mm vs. −0.01 mm, P=0.94) and restenosis rates (7.4% vs. 7.1%, P=1.0) were similar in both of the groups. Conclusion The application of oversized DCB at low pressure is effective and feasible for preventing late restenosis comparative to the standard technique of DCB.

A Safe and Simple Method for Ambulatory Iabp Placement Using Left Axillary-radial Technique

In patients with severe heart failure, a percutaneous axillary intra-aortic balloon pump (axIABP) may permit ambulation while awaiting destination therapy. Traditionally, an “axillary-femoral” approach has been used with femoral access for axillary angiography during insertion. Here we describe an “axillary-radial” technique for axIABP insertion and removal using left radial artery for second access. Insertion: Draping is performed to allow access to left axillary and radial arteries. A 5 Fr sheath is placed in the radial artery. Heparin is withheld until axillary access is obtained. Left distal subclavian angiography is performed via 4 French Pigtail to identify optimal IABP sheath insertion site avoiding major branches (Fig 1). A 0.018” wire via the radial sheath aids target artery identification with US (Fig 2A and B). A 5 Fr sheath is inserted into the axillary artery and the J-tipped 0.032” IABP guidewire is then advanced into the descending aorta using a JR4 diagnostic catheter to navigate the aortic arch. Sequential dilations allow easy insertion of the 8 Fr sheath. The proximal tip of the axIABP is placed near the level of the carina (Fig 4); a lower position may be considered if significant subclavian tortuosity is present. The external device is stabilized to the forearm with mild slack allowed to limit displacement during restricted arm movement. Anticoagulation is started after radial hemostasis is achieved. Removal: The axIABP is manually removed through the sheath, which remains in place, to simplify site sterilization. A 6 Fr sheath is placed in the left radial artery and an uninflated 7 mm x 40 mm balloon is positioned proximal to axillary sheath. If required, the balloon is repositioned over the arteriotomy and low-pressure inflation performed, assisting hemostasis should standard techniques fail. A Perclose device is deployed, and if successful, no balloon inflation is required. Final angiography through the balloon wire lumen is needed to confirm hemostasis without vascular complication. Generally, A 50cc Maquet Sensation Plus IABP is removable through the 8 Fr sheath. However, the 40cc IABP requires insertion of an 0.018” guidewire to maintain arterial access because the IABP cannot be easily removed through the 7.5 Fr sheath and they are often removed as a unit. Prior wire placement allows insertion of an 8 Fr sheath prior to suture closure. Periprocedural antibiotics are recommended in this instance. Conclusion: The left “axillary-radial” technique described here simplifies axIABP placement, post procedure hemostasis, overall procedural ergonomics and facilitates immediate ambulation.

Construction of modern wide, low-inflation pressure tyres per se does not affect soil stress

The interaction between rolling gear and soil is complex, but most important for the stress distribution in the soil profile. We explored the effect of three types of wide, low-inflation pressure tyres with similar dimensions on mean normal stress throughout the soil profile. We first tested the hypothesis that the stress is not affected by specific tyre-construction. Second, we tested the benefit of lowering the tyre inflation pressure to a minimum for the tyre with the lowest recommended inflation pressure. Finally, we tested the effect of tyres with similar tractive potential at different wheel loads, i.e. with a different weight-pull ratio. Stress measurements were made with Bolling probes at six positions simultaneously: both beneath the centreline (centre) and at 0.3 m lateral distance (+0.3 m) of the centreline of the wheel track, at 0.2, 0.4, and 0.6 m depth. The results revealed a very limited effect of tyre construction on mean normal stress. No differences were measured beneath the centre, and the differences at +0.3 m were found only at 0.2 m depth for the tyres at the rear axle. The effect of minimising tyre inflation pressure was limited to the upper parts of the soil profile for the measurements beneath the centre of the tyre (significant at 0.2 m depth and a trend at 0.4 m depth). Finally, our study did not reveal significant benefit of tyres with a lower wheel load while potentially having similar tractive performance, although the reduction of wheel load and associated lower inflation pressure potentially reduce stress in both top- and subsoil. The results emphasize that in order to reduce soil stress, tyre design and use should allow for a large contact area and low inflation pressure.

Reducing Tyre Hysteresis Losses using CuO Nanoparticles

Tyre is the contact part between the vehicle and road which provides various requirements of performance. Tyres are designed to absorb road irregularities, support vehicle load and provide braking/steering characteristics. An experimental test rig for single tyre test has been designed and constructed to evaluate the tyre performance characteristics under different operating conditions. The tyre load deflection characteristic has been examined by loading and unloading the tested tyre while resting on a hard surface at three inflation pressures. The results showed that the higher hysteresis losses were at tyre inflation pressure 20 psi. Three different percentages of CuO nanoparticles have been used to evaluate their effect on the tyre hysteresis losses. Transmission electron microscopy (TEM) has been performed for the analysis of nanoparticles size. Adding CuO nanoparticle in very small amounts with the enclosed air of the tested tyre can be useful for improving its performance significantly and decreasing the hysteresis losses. This has the potential for making use of the benefits of lower inflation pressure.

Controlled traffic farming delivers better crop yield of winter bean as a result of improved root development

This paper reports on the continuation of a long–term experiment on the effects of alternative field traffic systems (STP–random traffic with standard tyre inflation pressure, LTP–random traffic with low tyre inflation pressure and CTF–controlled traffic farming) on soil conditions and crop development as influenced by different tillage depths (DEEP–250 mm, SHALLOW–100 mm and ZERO–tillage), in a randomised 3 x 3 factorial design in 4 replicates launched by Harper Adams University in Edgmond, UK, in 2011. The results from season 2017–2018 revealed that CTF delivered 8% higher crop yield of winter field bean (Vicia faba) cv. Tundracomparing to STP (p = 0.005), i.e. 4.13 vs 3.82 tonnes ha-1respectively (at 14% moisture content). The ZERO–tillage plots featured significantly lower plant establishment percentage comparing to shallow and deep tillage: 79% vs 83% and 83% respectively (p = 0.012). The research showed that roots traits differed significantly between contrasting traffic at depths greater than 50mm with p < 0.05of: tap root biomass, number of lateral roots, biomass of lateral roots as well as total root biomass (tap+lateral roots),delivering significantly greater values of those before mentioned parameters on CTF comparing to STP. Tap root length significantly differed between traffic systems (p < 0.001)giving significantly greater results on CTF comparing to LTP and STP (17.7, 13.4 and 12.6 mm respectively). Significant differences in tap root diameter were found only at the depth of 100 mm (p < 0.001) where again CTF delivered significantly higher root diameter than the remaining 2 traffic systems.In the shallow layer of soil (0–50 mm) a significant difference was found only for tap root biomass, for interactions, where STP ZERO gave significantly higher results than STP SHALLOW and CTF SHALLOW (1.430, 0.733 and 0.716 g respectively).

Recent advances in understanding and managing postoperative respiratory problems.

Postoperative respiratory complications increase healthcare utilization (e.g. hospital length of stay, unplanned admission to intensive care or high-dependency units, and hospital readmission), mortality, and adverse discharge to a nursing home. Furthermore, they are associated with significant costs. Center-specific treatment guidelines may reduce risks and can be guided by a local champion with multidisciplinary involvement. Patients should be risk-stratified before surgery and offered anesthetic choices (such as regional anesthesia). It is established that laparoscopic surgery improves respiratory outcomes over open surgery but requires tailored anesthesia/ventilation strategies (positive end-expiratory pressure utilization and low inflation pressure). Interventions to optimize treatment include judicious use of intensive care, moderately restrictive fluid therapy, and appropriate neuromuscular blockade with adequate reversal. Patients’ ventilatory drive should be kept within a normal range wherever possible. High-dose opioids should be avoided, while volatile anesthetics appear to be lung protective. Tracheal extubation should occur in the reverse Trendelenburg position, and postoperative continuous positive airway pressure helps prevent airway collapse. In combination, all of these interventions facilitate early mobilization.

Measurement and Analysis of the Vertical Stress Distribution within a Cultivated Soil Volume under Static Conditions

Abstract. One of the important considerations of soil-tire interaction research is the stress distribution in the topsoil and within the cultivated soil volume due to tires. This stress distribution influences trafficability, ride performance, and tractive performance. In this study, a two-wheel-drive tractor and a group of piezoelectric pressure sensors were used at different tire loads and inflation pressures to (1) measure the vertical stress under three tire loads with three inflation pressures and determine the influence of these two parameters on the vertical stress in the topsoil, as measured by sensors with their upper surfaces at an initial depth of 50 mm within the soil volume; (2) develop an empirical relationship between the vertical stress and the depth beneath the soil surface, the tire load, the inflation pressure, and the lateral sensor distance from the tire centerline using multiple linear regression; and (3) analyze the effects of tire load and inflation pressure on vertical stress to contribute to the understanding of soil compaction processes based on the equation we developed. All vertical stress measurements were conducted when traffic was applied to the soil by the left front tire of the tractor, with forward motion of the tractor stopped before the left rear tire reached the sensors. The results indicated that (1) when the inflation pressure decreased, the soil-tire interface stress curve became smooth and the peak value of stress gradually moved to a point near the edge of the tire, whereas when the inflation pressure was higher, the peak stress value occurred in the center of the tire; (2) low inflation pressure significantly reduced the maximum vertical stress; (3) the vertical stress was influenced by all four factors investigated in this study; and (4) the stress within the soil volume varied as a quadratic function of the inflation pressure at a given tire load, and it varied as a linear function of tire load at a given inflation pressure. Keywords: Stress distribution, Tire load, Tire inflation pressure.

Rolling radii and moment arm of the wheel load for pneumatic tyres

Tractors and self-propelled harvesters are equipped with high volume pneumatic tyres with a low tyre inflation pressure. The contact patch can shift forwards or backwards in reference to the wheel centre as reaction on traction or brake forces because of the elastic tyre wall. Theoretical investigations – as necessary for modelling and simulation of dynamic vehicle behaviour – are complicated, since important tyre metrics cannot directly be measured based on the large deformations. Additionally, different definitions are often used. This is especially valid for the conversion of a drive torque into a traction force. In this context, the moment arm of the wheel load and the rolling radius of the tyre at zero slip condition are especially important. In contrast to the hitherto existing perception, the magnitude and position of the moment arm of the wheel load in reference to the wheel centre is dependent on traction and brake forces in addition to the motion resistance. The rolling radius of an elastic pneumatic tyre can be interpreted as radius of a fictitious rigid substitute wheel. This contribution emphasizes the outstanding importance of the rolling radius rdyn for all calculations on pneumatic tyres and the important roll of the variable moment arm of the wheel load for the moment compensation on the wheel.