Optimal Clearance Research Articles

Research and Application of Euler Cutting Path Based Optimisation Algorithm with Greedy-RRT Algorithm

With the development of social economy, mould processing enterprises have an increasingly strong demand for reducing costs and improving economic efficiency. The optimisation of steel plate cutting path is one of the key links to improve production efficiency. In this paper, the optimal cutting path problem of steel plate under different cutting tasks is investigated, and the optimal cutting path under complex geometries is found through various optimisation algorithms. For cutting task N3, the cutting path is divided into outer contour cutting, inner hole cutting and inner hole part cutting. According to the problem, all rectangular parts inside the ellipse need to be cut before the ellipse. Through the Eulerian cutting path optimisation algorithm, we solve the air-travel problem between the inner holes and the outer contour as well as the air-travel problem between the inner holes of the ellipse and the parts inside the ellipse. The total length of the finally determined optimal air-travel path is 97 units. By combining the greedy algorithm and the RRT algorithm, we determine the number and location of the bridges and design the optimal cutting path starting from the lower right corner of the steel plate. The final clearance of the bridges is 4 units, the total length of the combined optimal path clearance is 35.56 units, and the number of bridges is 8, which are located between adjacent rectangles.

Study on vibration mechanism and dynamic characteristics for TBM main bearing defects

As the key component of TBM main driving system, the main bearing plays an indispensable role both in its service life and the normal operation of the TBM. While prior investigations predominantly focused on static analyses of the main bearing, only a scant few delved into its dynamic characteristics and the vibration mechanism. In order to explore the dynamic characteristics of TBM main bearing, a comprehensive dynamics model of the TBM main bearing considering local defects is established, the vibration mechanism of the main bearing with local defects is revealed, and the influence of uneven load is investigated. Furthermore, the effects of roller wear and bearing clearance on the vibration response of the main bearing are analyzed, which systematically describes the real motion of the main bearing. Finally, a main bearing scaling test rig is constructed, and the proposed model is validated through experiments and simulations, demonstrating its good accuracy. In addition, the results show that the incremental imposition of uneven load correlated with a rising trend in the root mean square (RMS) value of vibration response. Moreover, maintaining an optimal axial clearance is pivotal in ensuring the reliable operation of the main bearing. The research work in this paper provides theoretical scaffolding for the defect diagnosis of TBM main bearing, whilst also serves as an analytical cornerstone for future explorations into the dynamics of various types of thrust bearings.

Activating FcγRs on monocytes are necessary for optimal Mayaro virus clearance.

Mayaro virus (MAYV) is an emerging arbovirus. Previous studies have shown antibody Fc effector functions are critical for optimal monoclonal antibody-mediated protection against alphaviruses; however, the requirement of Fc gamma receptors (FcγRs) for protection during natural infection has not been evaluated. Here, we showed mice lacking activating FcγRs (FcRγ-/-) developed prolonged clinical disease with more virus in joint-associated tissues. Viral clearance was associated with anti-MAYV cell surface binding rather than neutralizing antibodies. Lack of Fc-FcγR engagement increased the number of monocytes through chronic timepoints. Single cell RNA sequencing showed elevated levels of pro-inflammatory monocytes in joint-associated tissue with increased MAYV RNA present in FcRγ-/- monocytes and macrophages. Transfer of FcRγ-/- monocytes into wild type animals was sufficient to increase virus in joint-associated tissue. Overall, this study suggests that engagement of antibody Fc with activating FcγRs promotes protective responses during MAYV infection and prevents monocytes from being potential targets of infection.

Experimental study on the influence of radial internal clearances of the rolling bearings on dynamics of a flexible rotor system

To investigate the impact of radial internal clearance of rolling bearings on the dynamic response of a flexible rotor system in a turbo-shaft engine, a dynamic similarity model of the power turbine rotor was established. Experimental research was then conducted. Four rolling bearings supporting the rotor were examined, with dynamic response tests carried out under varying radial internal clearances. The influence of the radial internal clearance on the dynamic characteristics of the rotor system was studied using the controlled variable method. The amplitude, orbit, and asynchronous vibration were analyzed through time-domain signal comparison, waterfall diagrams, and spectral analysis. The experimental results demonstrate that: (1) Adjusting the radial internal clearance of the bearings can significantly reduce the dynamic response of the flexible rotor system, with a maximum observed displacement response reduction of 88%. (2) The efficiency of vibration reduction is closely related to the axial location of the bearing. (3) Optimal radial internal clearance is not necessarily achieved at the maximum or minimum values. (4) The "locked-up" frequency phenomenon, which increases the resonance opportunities of the rotor system, can be mitigated by adjusting the radial internal clearance of different bearings. This research is of great significance and engineering value for understanding, diagnosing, and preventing excessive vibration in flexible rotor systems.

A contemporary step-by-step guide to performing flexible ureterorenoscopy for renal calculi

Abstract With advancements in laser technology and urological techniques, flexible ureterorenoscopy has emerged as a vital surgical approach for managing stone disease. Various techniques can be employed to customize endourological stone treatments. Despite the continuous evolution of equipment, it remains crucial to comprehend the fundamental steps of the procedure. This paper offers a comprehensive step-by-step guide that integrates the latest advancements in both scopes and lasers. Additionally, it outlines potential pitfalls and strategies to circumvent them, aiming to achieve optimal stone clearance and deliver individualized patient care safely and efficiently.

Surface ligand-regulated renal clearance of MRI/SPECT dual-modality nanoprobes for tumor imaging

BackgroundThe general sluggish clearance kinetics of functional inorganic nanoparticles tend to raise potential biosafety concerns for in vivo applications. Renal clearance is a possible elimination pathway for functional inorganic nanoparticles delivered through intravenous injection, but largely depending on the surface physical chemical properties of a given particle apart from its size and shape.ResultsIn this study, three small-molecule ligands that bear a diphosphonate (DP) group, but different terminal groups on the other side, i.e., anionic, cationic, and zwitterionic groups, were synthesized and used to modify ultrasmall Fe3O4 nanoparticles for evaluating the surface structure-dependent renal clearance behaviors. Systematic studies suggested that the variation of the surface ligands did not significantly increase the hydrodynamic diameter of ultrasmall Fe3O4 nanoparticles, nor influence their magnetic resonance imaging (MRI) contrast enhancement effects. Among the three particle samples, Fe3O4 nanoparticle coated with zwitterionic ligands, i.e., Fe3O4@DMSA, exhibited optimal renal clearance efficiency and reduced reticuloendothelial uptake. Therefore, this sample was further labeled with 99mTc through the DP moieties to achieve a renal-clearable MRI/single-photon emission computed tomography (SPECT) dual-modality imaging nanoprobe. The resulting nanoprobe showed satisfactory imaging capacities in a 4T1 xenograft tumor mouse model. Furthermore, the biocompatibility of Fe3O4@DMSA was evaluated both in vitro and in vivo through safety assessment experiments.ConclusionsWe believe that the current investigations offer a simple and effective strategy for constructing renal-clearable nanoparticles for precise disease diagnosis.Graphical

Investigation of the effects of radial clearance on the screw conveyor performances for different inclinations

Screw conveyors are widely used for bulk material transportation. This study investigates the critical role of radial clearance, the gap between the screw and the conveyor body, on performance across various inclination angles. The Discrete Element Method (DEM) is employed to analyze the effects of different radial clearances on conveyor performance for concrete aggregate and sand as bulk materials. Volumetric efficiencies and capacity losses serve as key performance indicators, quantitatively assessed for each radial clearance and inclination combination. Experimental validation is conducted to corroborate the findings. In the study, the optimal radial clearance was identified as 1.5 to 3 times of the particle size. This optimal clearance minimizes the material jamming and increases the performance for screw conveyors with different inclinations and bulk material types as a result.

An imbalance multi-faults data transfer learning diagnosis method based on finite element simulation optimization model of rolling bearing

In practical engineering applications, rotating machinery is often in a healthy state, with more healthy samples and fewer multi-faults samples, which leads to be misdiagnosed. A finite element simulation model (FEM) is proposed to expand imbalanced multi-faults sample data. However, there is a significant difference in vibration response between the FEM simulation data and the measured data collected on the rotating machinery. Therefore, a method based on vibration response eigenvalue model correction has been adopted, aiming to narrow the gap between the simulation data and the measured data. In order to solve the problem of low accuracy of sample imbalance fault diagnosis under different working conditions, a transfer learning (TL) fault diagnosis method based on finite element simulation optimization model of rolling bearings to supplement imbalanced multi-fault data is proposed. Firstly, the FEM of healthy bearings is established, and the optimal radial clearance of bearings is obtained by modifying the vibration response eigenvalue model. Then, corresponding simulated fault vibration responses were obtained by setting composite faults on the optimal model. Finally, supplementing the unbalanced fault data with simulation data to create a mixed balanced dataset as samples, the TL model is trained to accomplish intelligent fault diagnosis for multi-faults. The experimental results show that using mixed data as training samples to train neural network models can improve the accuracy of transfer learning fault diagnosis by over 10%. Expanding fault samples by modifying the bearing clearance of the FEM is an effective method to address sample imbalance.

Managing Replenishment and Clearance of Perishables: Last-In, First-Out (LIFO) Issuing Policy and Age-Sensitive Demand

In supermarkets, customers choose the unit(s) they purchase, which leads to inventory being sold in a last-in, first-out (LIFO) order for perishable products. Furthermore, for such products, the demand for inventory may depend on its age since customers may choose to walk away if the freshest available inventory is too old for them. Despite the widespread occurrence of LIFO-based inventory systems, few studies have analyzed them. In this study, we contribute by developing insights on joint replenishment and clearance policy for a perishable product with a general, finite lifetime using a periodic review model such that the inventory is sold in a LIFO order and demand is age-dependent. The model seeks to optimize two decisions every period: how much of fresh inventory to order and how much of existing inventory to clear. A key objective of the model is to understand the effect of age-dependence of demand on the optimal replenishment and clearance policy. We find that the optimal clearance policy for all but the oldest inventory is a multiindex policy such that between any pair of adjacent indexes, either no inventory is cleared or all the inventory is cleared till the lower index. For the oldest inventory, we show that the optimal policy may have multiple forms depending on how sensitive demand is to inventory’s age. This is a notable result in inventory theory since parameters usually affect only the policy value(s) and not the policy structure. Since the optimal policy has a complex structure in general, which makes it difficult to compute, we develop an efficient heuristic to compute the replenishment and clearance quantities. The heuristic underperforms the optimal policy by [Formula: see text]0.92% on average.

INOS is necessary for GBP-mediated T. gondii clearance in murine macrophages via vacuole nitration and intravacuolar network collapse

Toxoplasma gondii is an obligate intracellular parasite of rodents and humans. Interferon-inducible guanylate binding proteins (GBPs) are mediators of T. gondii clearance, however, this mechanism is incomplete. Here, using automated spatially targeted optical micro proteomics we demonstrate that inducible nitric oxide synthetase (iNOS) is highly enriched at GBP2+ parasitophorous vacuoles (PV) in murine macrophages. iNOS expression in macrophages is necessary to limit T. gondii load in vivo and in vitro. Although iNOS activity is dispensable for GBP2 recruitment and PV membrane ruffling; parasites can replicate, egress and shed GBP2 when iNOS is inhibited. T. gondii clearance by iNOS requires nitric oxide, leading to nitration of the PV and collapse of the intravacuolar network of membranes in a chromosome 3 GBP-dependent manner. We conclude that reactive nitrogen species generated by iNOS cooperate with GBPs to target distinct structures in the PV that are necessary for optimal parasite clearance in macrophages.

Multimodality Imaging to Direct Management of Primary and Recurrent Rectal Adenocarcinoma Beyond the Total Mesorectal Excision Plane.

Rectal tumors extending beyond the total mesorectal excision (TME) plane (beyond-TME) require particular multidisciplinary expertise and oncologic considerations when planning treatment. Imaging is used at all stages of the pathway, such as local tumor staging/restaging, creating an imaging-based "roadmap" to plan surgery for optimal tumor clearance, identifying treatment-related complications, which may be suitable for radiology-guided intervention, and to detect recurrent or metastatic disease, which may be suitable for radiology-guided ablative therapies. Beyond-TME and exenterative surgery have gained acceptance as potentially curative procedures for advanced tumors. Understanding the role, techniques, and pitfalls of current imaging techniques is important for both radiologists involved in the treatment of these patients and general radiologists who may encounter patients undergoing surveillance or patients presenting with surgical complications or intercurrent abdominal pathology. This review aims to outline the current and emerging roles of imaging in patients with beyond-TME and recurrent rectal malignancy, focusing on practical tips for image interpretation and surgical planning in the beyond-TME setting. Keywords: Abdomen/GI, Rectum, Oncology © RSNA, 2024.

Structural Optimization of the Main Bearing in a Tunnel Boring Machine Considering Clearance

Abstract An optimal design method for the main bearing of a tunnel boring machine is proposed. In this method, the fatigue life is used as the objective function. Structural parameters, including clearance, are considered as design variables. First, a quasi-static model of the main bearing and a calculation model of the fatigue life are established. The correctness of the theoretical method is verified by comparing it with the calculation results of the finite element method. Next, the influence of clearance on the load-carrying performance under external loads is analyzed. There is an optimal negative clearance for the axial loaded and radial rows. With the increase in the external loads, the optimal negative clearance gradually decreases. The variation laws of the load-carrying performance for the axial loaded and supporting rows affected by axial clearance mainly depend on the bias load degree of the main bearing. Finally, based on the optimal design model of the main bearing, the optimal internal structure is obtained using the genetic algorithm. The optimized fatigue life is improved by 92.2%. The load-carrying performance of the optimal main bearing has also been significantly enhanced compared to the initial design. Therefore, the proposed optimization method provides a practical approach to the main bearing design.

Functional, Oncological, and Radiological Outcomes Following Safe Surgical Dislocation for the Treatment of Locally Aggressive Proximal Femoral Lesions

Abstract Study Type: Retrospective cohort study. Background and Purpose: Locally aggressive lesions of the proximal femur represent a spectrum of pathologies in the younger age group, which result in large defects. Safe surgical dislocation (SSD) is one of the viable surgical approaches to achieve optimal visualization and clearance of tumor. This study looks at the functional, oncological, and radiological outcomes following SSD for the treatment of locally aggressive proximal femoral lesions. Materials and Methods: A retrospective study was done in Orthopedics Unit 3 at our tertiary care center between 2015 and 2021 on patients who underwent SSD for the treatment of biopsy confirmed locally aggressive proximal femur lesions. The inclusion criteria were age more than 15 years, with biopsy confirmed symptomatic locally aggressive lesions of the proximal femoral region with a minimum 1 year follow-up. The clinical parameters were reduction in pain, restoration of hip movements, abductor strength, and ability to weight bear and resumption of activities of daily living. Graft consolidation, status of implant, local recurrence, trochanteric nonunion, and appearance of avascular necrosis included as radiological parameters. The functional parameters were assessed through the modified Musculoskeletal Tumor Society Score and the nonarthritic Young Hip Score. Results: Ten cases of biopsy-proven proximal femoral lesions (out of 15 such cases) fulfilling the inclusion criteria were enrolled. All ten underwent intralesional excision/extended curettage of lesion, followed by auto/allograft reinforcement to fill the defect and internal fixation using SSD as surgical approach. The choice of graft and fixation method was based on surgeon’s preference. Functional and radiographic assessment was done on follow-up, with an average follow-up of 13 months (range 12–14 months). The mean nonarthritic Young Hip Score improved from 49 (±8.96) preoperatively to 85.4 (±11.95) at the time of review, and the modified Musculoskeletal Tumor Society Score improved from a mean of 23.3 (±0.83) preoperatively to 28.4 (±1.07) at the time of review. There was no tumor recurrence and avscular necrosis at the time of follow-up. Allograft consolidation was seen in 8 out of 10 cases at the time of review. Conclusion: SSD is an excellent approach to achieve optimal tumor clearance. Good functional and radiological outcomes are seen if adequate tumor clearance is obtained and reconstruction with stable internal fixation is achieved. Tumor recurrence and avascular necrosis were not noted in any of the cases at 1-year (intermedial) follow-up.

Survival Dynamics in Advanced Ovarian Cancer: R2 Resection Versus No-Surgery Paths Explored.

Cytoreductive surgery is critical for optimal tumor clearance in advanced epithelial ovarian cancer (EOC). Despite best efforts, some patients may experience R2 (>1cm) resection, while others may not undergo surgery at all. We aimed to compare outcomes between advanced EOC patients undergoing R2 resection and those who had no surgery. Retrospective data from 51 patients with R2 resection were compared to 122 patients with no surgery between January 2015 and December 2019 at a UK tertiary referral centre. Progression-free survival (PFS) and overall survival (OS) were the study endpoints. Principal Component Analysis and Term Frequency - Inverse Document Frequency scores were utilized for data discrimination and prediction of R>2cm from computed tomography pre-operative reports, respectively. No statistical significance was observed, except for age (73 vs 67years in the no- surgery vs R2 group, P: .001). Principal Components explained 34% of data variances. Reasons for no surgery included age, co-morbidities, patient preference, refractory disease, patient deterioration or disease progression, and absence of measurable intra- abdominal disease). The median PFS and OS were 12 and 14months for no-surgery, vs 14 and 26months for R2 (P: .138 and P: .001, respectively). Serous histology and performance status independently predicted PFS in both no-surgery and R2 cohorts. In the no-surgery cohort, serous histology independently predicted OS, while in the R2 cohorts, both serous histology and adjuvant chemotherapy were independent prognostic features for OS. The bi-grams "abdominopelvic ascites" and "solid omental" were amongst those best discriminating between R>2cm and R1-2cm. R2 resection and no-surgery cohorts displayed unfavourable prognosis with a notable degree of uniformity. When cytoreduction results in suboptimal results, the survival benefit may still be higher compared to those who underwent no surgery.

Understanding ureteroscopy complications according to modified Clavien classification system.

To determine the complications of ureteric stone treatment with semi-rigid uretero-renoscopy in accordance with the modified Clavien classification system. The descriptive, prospective study was conducted at the Department of Urology, Sindh Institute of Urology and Transplantation, Karachi, from June 30, 2020, to December 29, 2021, and comprised patients of either gender aged 18-70 years having ureteric stones. All patients were subjected to ureterorenoscopy using a semi-rigid ureteroscope under general anaesthesia. The patients were followed up for 2 months. All complications were noted and graded in line with the Modified Clavien Complication System. Ultrasound and X-ray were used to determine the stone-free rate. Data was analysed using SPSS 23. Of the 414 patients, 304(73.4%) were males and 110(26.5%) were females. The overall mean age was 40.22±13.10 years. There were 106(25.6%) proximal, 134(32.3%) middle, and 174(42%) distal ureteric stones. Stent placement was done in 56(13.5%) cases. There were 260(62.8%) patients with no complication, 90(21.7%) with grade I complications, 34(8.2%) with grade II complications, 10(2.4%) with grade IIIa, 8(1.9%) with grade IIIb, and 12 (2.9%) with grade IVa complications. Uretero-renoscopy was found to be a safe procedure, as it had minimal associated complications with optimal stone clearance and great dexterity. The Modified Clavien classification system was found to be an easy way to classify surgical complications of uretero-renoscopy.

The Influence of Blade Tip Clearance on the Flow Field Characteristics of the Gas–Liquid Multiphase Pump

Gas–liquid multiphase pumps are critical transportation devices in the petroleum and chemical engineering industries, and improving their conveyance efficiency is crucial. This study investigates the influence of blade tip clearance variations on the flow characteristics within a multiphase pump. Numerical simulations were conducted using Eulerian two-phase and SST k-ω turbulence models with four distinct tip clearance sizes (0 mm, 0.3 mm, 0.6 mm, and 0.9 mm). The performance curve, tip leakage flow (TLF), and internal gas distribution were subjected to analysis. The results indicate that the TLF is linearly related to the clearance size and traverses multiple flow passages, resulting in energy losses and a reduced pump head coefficient. Larger tip clearances (0.6 mm and 0.9 mm) exhibited a more uniform flow pattern, contrasting the irregularities seen with a 0.3 mm clearance. Compared to no tip clearance (0 mm), gas holdup within the impeller passages decreased by 18.39%, 39.62%, and 58.53% for clearances of 0.3 mm, 0.6 mm, and 0.9 mm, respectively, leading to decreased overall system efficiency. This study highlights the connection between tip clearance size and flow dynamics in multiphase pumps, offering insights for optimal tip clearance selection during multiphase pump design.

Role of tip leakage flow in an ultra-highly loaded transonic rotor aerodynamics

Tip clearance size is a very critical design parameter for the modern transonic rotor. This investigation attempts to reveal the role of tip leakage flow in an ultra-highly loaded low reaction transonic rotor (loading coefficient equals to 0.782) aerodynamics. Flow fields in the rotor with varied tip clearance sizes, ranging from 0 to 3 times of the datum case, are discussed at length. Both performance variation and stall mechanisms involved are elaborated. As a result, the rotor performance presents a continuous decline with the increased tip clearance size as a result of the additional secondary flow loss induced by the tip leakage flow. While for stall margin, an optimal tip clearance size exists, and it happens to be the datum case. The tip leakage flow is found to have the ability to blow away the low-energy flow accumulated in the rotor tip suction side. Specially, the forward portion of tip leakage flow plays the dominate role in extending the rotor stall margin. However, as the tip clearance size exceeds the datum case, the shock-tip leakage vortex interaction causes the tip leakage vortex breakdown and the stall margin is hence narrowed.

Optimal shape design of spherical squeeze film bearings using genetic algorithms

The optimal shape design of hydrodynamic axisymmetric spherical bearings under conditions of transient axisymmetric pure squeeze is investigated using genetic algorithms (GA). The optimization problem is to determine the radial clearance shape which maximizes the load impulse resulting from transient ball motion to a target minimum film thickness specification. For fully-hemispherical cups, non-dimensional analysis shows that GA-based optimal designs yield significantly larger non-dimensional impulse values when compared with those obtained either randomly or from optimal ellipsoidal geometry. A sample design application with specified load history shows that an optimal GA-inspired composite clearance specification amenable to fabrication can be constructed from preferred features obtained from the GA-based optimal shapes. The optimal composite shape design is shown to provide significantly better bearing performance, as measured by minimum film thickness, after a specified time interval than an optimal ellipsoidal design. The optimal composite shape design is also found to be less sensitive to realistic deviations in clearance shape, load impulse, and viscosity variation when compared with similar variations to an optimal ellipsoidal cup design.

Low-energy defibrillation using a base-apex epicardial electrode.

Current implantable cardioverter defibrillators (ICDs) require electric conduction with high voltage and high energy, which can impair cardiac function and induce another malignant arrhythmia. As a result, there has been a demand for an ICD that can effectively operate with lower energy to mitigate the risks of a strong electric shock. A pair of sheet-shaped electrodes covering the heart were analyzed in three configurations (top-bottom, left-right, and front-back) using a heart simulator. We also varied the distance between the two electrodes (clearance) to identify the electrode shape with the lowest defibrillation threshold (DFT). We also investigated the ICD shock waveform, shock direction, and the effect of the backside insulator of the electrode. The DFT was high when the clearance was too small and the DFT was high even when the clearance was too large, suggesting that an optimal value clearance. The top-bottom electrodes with optimal clearance showed the lowest DFT when the biphasic shocks set the top electrode to a high potential first and then the bottom electrode was set to a high potential. An interval between a first shock waveform and a second shock waveform should be provided for low-energy defibrillation. Because the insulator prevents unnecessary current flow to the backside, the DFT of the electrodes with insulators is less than those without insulators. Painless defibrillation using sheet-shaped electrodes on the epicardium is predicated on the basis of results using a heart simulator.

Performance enhancement of a Wells turbine using CFD-optimization algorithms coupling

Wells turbine is a popular device for converting wave energy. The current work aims to maximize the power a Wells turbine generates using a response surface optimization method based on computational fluid dynamics (CFD). The ANSYS software's response surface optimization toolbox was employed in this investigation. The Wells turbine received a performance boost using the variable tip clearance design. Input parameters for the optimization technique included two variable tip clearance design parameters. The major objective of the optimization process was to maximize the torque coefficient (CT) of the Wells turbine. The results showed that the optimal design boosted the average and maximum torque coefficients of the modified Wells turbine by 37.31% and 76.16%, respectively.Furthermore, the improved turbine has a 33.33% wider operating range (OR) than the baseline. At φ equals 0.225, 0.250, and 0.275, the improved Wells turbine's efficiency rose by 19.53%, 71.67%, and 80.38%, respectively. Using the optimal design, 92.2% more power was generated from the modified Wells turbine. Based on a detailed flow analysis, the flow separation zone around the blade tip was reduced, and the optimal variable tip clearance design postponed the stall onset point.