Torque ripple attenuation for an axial piston swash plate type hydrostatic pump: noise considerations

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (February 28, 2007).Vita.Thesis (Ph.D.) University of Missouri-Columbia 2006.The main goal of this work is to reduce the disturbing noise generated by axial piston swash plate type hydrostatic pumps by attenuating the shaft torque variation. The analysis begins by deriving the equation of the shaft torque as a function of the average torque and the total number of pistons that are used within the rotating group. A swash plate control law is derived according to which if the swash plate is adjusted continuously, would give a constant shaft torque. In a second method, it is shown that with the use of an optimized index angle, the torque ripple amplitude for a tandem pump could be reduced by as much as 75%. The results from a Simulink[copyright] model of a nine piston pump with leakage and fluid compressibility effects support the analytical conclusions. It is also shown that there is a link between the torque ripple and flow ripple; hence the torque ripple attenuation results in the flow ripple attenuation too.Includes bibliographical reference

IMECE2005-79627 Torque Ripple Attenuation of an Axial Piston Pump by Continuous Swash Plate Adjustment

Abstract One of the major drawbacks of a hydraulic system is the disturbing noise generated by the hydraulic pump. Based on the accepted theory about noise generation in an axial piston pump, various studies suggesting modification of the port-plate relief groove geometry and addition of hydraulic attenuators have shown a limited success in reducing the noise. The noise level is still high and may not be acceptable for future applications. A recent industrial study shows that the noise apparently has relation with the torque acting on the input shaft of the axial piston pump. The primary objective of this paper is to describe a new method to reduce the noise level by varying the swash plate of the pump continuously to eliminate the torque ripple. The paper begins by deriving the equation of torque acting on the input shaft as a function of the average torque and the total number of pistons that are used within the rotating group. A control law is derived according to which if the swash plate is dithered, should give a constant shaft torque. By attenuating the torque ripple characteristics of the pump, other vibrational aspects of the pump are also expected to be reduced. The secondary objective of this paper is to present a Simulink® model of a nine piston pump to describe a functional pump. The swash plate control law earlier derived will be applied to this model to see the behavior of the output parameters like the shaft torque, output flow and pressure. The results will be investigated to see if any relationship exist between the pump torque ripple and pressure ripple, and the theory of pump noise attenuation by reduction in torque ripple will be corroborated

Intra- and Interobserver Reliability of Bone Volume Estimation Using OsiriX Software in Patients with Cleft Lip and Palate Using Cone Beam Computed Tomography

The objective of the current study was to evaluate intra- and interobserver bone volume measurements and effect of orientation on the reliability of bone volume evaluation in as-acquired vis-à-vis oriented cone beam computed tomography scans using Osirix software and possible correlation between gender, age, and bone volume required. For this, 31 cone beam computed tomography (CBCT) scans of 14 girls and 17 boys (aged 9–13) with unilateral cleft lip and/or palate who met the inclusion criteria were analyzed. Efficacy and reliability of third party software Osirix for bone volume calculation was assessed using as acquired and oriented volumes by three specialists (a radiologist, an orthodontist, and an oral maxillofacial surgeon). The dataset and readings were anonymized to prevent any bias. Two-way mixed model analysis on as-acquired and oriented observations exhibited intra-class coefficient (ICC) values ≥ 0.90. Wilcoxon signed rank test (p = 0.10) and Kruskal–Wallis ANOVA (p = 0.46) indicated that although a clinical difference in volume assessment was seen between as-acquired and oriented observations (inter-observer and intra-observer), it was statistically insignificant. Spearman’s bi-variate correlation analysis revealed a significant relation between the type (side) of cleft and bone volume required to fill the defect (p < 0.05). Although there was clinical difference in bone volume measurement by the three observers, it was insignificant statistically. Clefts on the left side in the patients had significantly more bone required than the right side, whereas age and gender had no relation with bone needed to fill the defect. OsiriX software provided good reliability in measurements of bone volume

Midterm postoperative outcomes of different types of surgical reconstruction of sinus venosus atrial septal defects with anomalous pulmonary venous connection: The Results of Prospective Cohort Study

Abstract Background and Aims Sinus venosus atrial septal defects (SVASDs) constitute a substantial part of atrial septal defects and are usually characterized by anomalous pulmonary venous connection (APVC), causing complications like sinus node dysfunction and arrhythmias. Several surgical approaches are used for treating SVASDs in pediatric patients, including single‐ and two‐patch techniques. The study aimed to prospectively evaluate and compare the safety and efficacy of these two methods with different follow‐up periods. Methods Ten patients aged 1–8 years with SVASDs and partial APVC were enrolled in the study at Bhanubhai and Madhuben Patel Cardiac Centre, Karamsad, India, between December 2018 and October 2021. The single‐patch (sandwich‐patch) technique was used in two patients, whereas the two‐patch (dual‐patch) technique with autologous pericardium was used in seven. Safety was assessed as the absence of complications in the follow‐up periods of 6 months, 1, and 2 years, whereas efficacy was estimated by the preserved sinus rhythm and the development of arrhythmias. Electrocardiographic and echocardiographic methods were used to evaluate both parameters. Results No deaths, reoperations, pulmonary vein, and superior vena cava (SVC) stenosis or phrenic nerve palsy were observed among the 10 patients in the three follow‐up periods. Sinus rhythm was arrested in two of the seven patients who underwent two‐patch repair, whereas no rhythm disturbances occurred in those who underwent single‐patch repair. Conclusion Both techniques used in SVASD repair with autologous pericardium proved to cause the smaller rate of complications in midterm postsurgical phase. However, there is a potentially great risk of the development of sinus node malfunction after the application of the two‐patch technique. Therefore, methods avoiding sinus node interference are preferred in patients with partial APVC involving SVC