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Full ceramic ball bearings are widely used in extreme and complex conditions, such as ultra-high/low temperature, ultra-high speed, corrosion and insulation, because of their material specificity. In order to reveal the friction and lubrication properties, improve the service performance life of all ceramic ball bearings, a mathematical model of the oil lubrication for full ceramic ball bearings has been established in this paper. The distribution rule of the lubricant film in the contact area under different speeds and loads were analysed. The main factors influencing the peak mutation of the lubricant film pressure are clearly defined. The results are compared and analysed by using a ball-disc rolling lubricant film test machine. The study found that the thickness of the lubricant film of a full ceramic ball bearing is positively correlated with the bearing speed and negatively correlated with the bearing loads. The bearing speed has a relatively large effect on the change in the lubricant film thickness. The pressure of the lubricant film in the contact area is positively correlated with the bearing speed, but it is not affected by the bearing load. Unlike metal ball bearings, the thickness and pressure of the lubricant film have a greater relative rate of change in different positions in the contact area of full ceramic ball bearings. With an increase in the bearing speed, the necking-down effect has a greater influence on the peak mutation of the oil pressure. Only one pressure peak occurs in the oil film in the contact area. The results of this paper play an important role in revealing the friction and lubrication properties of full ceramic ball bearings and improving their service performance and life under oil lubrication conditions.

Improving compactness is essential for high-power microwave (HPM) sources. In this paper, a novel reflective modulation cavity is proposed and investigated in a V-band relativistic coaxial transit-time oscillator (RCTTO). The cold cavity analyses and particle-in-cell simulations show that the reflective modulation cavity has larger reflection coefficients of TEM mode and stronger electron beam modulation capability when compared with a uniform modulation cavity. When the input diode voltage is 391 kV, the beam current is 4.91 kA, and when the guiding magnetic field is 0.6 T, the compact V-band RCTTO produces an output microwave power of 518 MW (conversion efficiency of 27.0%). Compared with the original RCTTO, the compact V-band RCTTO featuring a reflective modulation cavity exhibits a 24.8% increase in output power and a 5.4% improvement in efficiency, and the axial length of the magnetic field uniform region is reduced by 24.2%. The compact V-band RCTTO also demonstrates a broad operation voltage range, indicating potential for stable operation with voltage fluctuations in experiments. Furthermore, the reflective modulation cavity can be integrated into other high-frequency O-type HPM devices to enhance compactness, thereby diminishing the demands on the magnetic field region, which is advantageous for the future permanent packaging of HPM sources. [ABSTRACT FROM AUTHOR]

This paper aims to obtain the best shape accuracy evaluation algorithm for silicon nitride ceramic balls after lapping, and to extract the initial signal of the ball surface to improve the accuracy and reliability of the algorithm. The research methods of this paper are as follows: Firstly, an analysis of the uniform envelope of the lapping trajectory of ceramic balls is carried out to verify whether the lapping trajectory after processing can achieve a consistent envelope on the balls' surface. On this basis, it is found through experiments that the standard deviation SD between the roundness deviations of different contour sections is small. The value is maintained at approximately 0.03 μm, and the roundness deviation can approximately replace the spherical deviation. Then the different contour sections of the sphere are sampled by the Taylor roundness instrument. Considering the uncertainty, the sampling points of different contour sections are averaged and used as the original signal of the sphere surface. Then the EMD method is used to process the signal to be detected on the sphere surface. The initial signal of the sphere surface is extracted by judging whether the number of ripples Kc obtained by decomposition is greater than the critical value. Then the initial signal is used as the input value of the approximation algorithm. Through the roundness deviation approximation algorithm based on the least square method, the given minimum approximation domain range is finely processed. The divided fine points are used as the center of the circle to intersect with the initial signal. The maximum, minimum, and range of each circle are calculated to obtain the roundness error based on the minimum circumscribed circle, the maximum inscribed circle, and the minimum region method. Finally, the calculated values are compared with those obtained by the traditional algorithm. The experimental results of this paper show that the algorithm is consistent with the roundness error measured by the instrument, compared with the mainstream evaluation criteria. In summary, the conclusions can be drawn as follows: Through a large number of experimental cases and comparative experiments, the algorithm has high accuracy and reliability. The research results of this paper have essential reference significance for accurately evaluating the shape accuracy of ceramic balls in actual production. [ABSTRACT FROM AUTHOR]

Background: This study aims to investigate the effectiveness of application of single-port thoracoscopy using the subxiphoid approach in anterior mediastinal tumor surgery., Methods: Between June 2014 and June 2016, a total of 108 patients (59 males, 49 females; mean age: 64.9±7.5 years; range, 45 to 79 years) with anterior mediastinal tumors were randomized into subxiphoid (experimental) or right chest (control) groups. Single-port thoracoscopy using the subxiphoid approach was performed in the subxiphoid group, while thoracoscopy using the right thoracic approach was performed in the control group. Preand postoperative pain stress indicators, Visual Analog Scale scores, quality of life scores, postoperative tumor recurrence, and five-year survival rates were compared between the groups., Results: There were no mortality or serious complications in either group. The mean Visual Analog Scale pain scores on postoperative Days 1 and 7 were 6.5±0.8 and 2.9±0.8 in the subxiphoid group, respectively, compared to 7.2±0.8 and 3.4±0.8 in the control group (p<0.05 for all), respectively. The mean quality of life scores on postoperative Days 1 and 7 were 81.5±5.0 and 79.3±7.7, respectively, in the subxiphoid group compared to 72.4±4.3 and 71.3±4.8 in the control group, respectively (p<0.05 for all). Postoperative pain and pain mediator indexes were lower in the subxiphoid group (p<0.05 for all). The postoperative tumor recurrence rates were 3.70% and 20.37% in the subxiphoid and control groups, respectively (p=0.008). The five-year survival rates were 85.2% and 63.0% in the subxiphoid and control groups, respectively (p=0.008)., Conclusion: Single-port thoracoscopy using the subxiphoid approach is technically feasible, safe, and effective in performing surgery for anterior mediastinal tumors with an intact capsule and a tumor diameter of ≤5 cm., Competing Interests: Conflict of Interest: The authors declared no conflicts of interest with respect to the authorship and/or publication of this article., (Copyright © 2023, Turkish Society of Cardiovascular Surgery.)

A supercontinuum (SC) source spanning from 2 to 4 μm is demonstrated in As 2 S 3 -chalcogenide fibers pumped by a nanosecond supercontinuum pump source in the normal dispersion region. In this experiment, two pieces of 3-m-long step-index As 2 S 3 fiber with different core diameters of 7 μm and 9 μm are pumped by a 1.9-2.5 μm nanosecond supercontinuum source. The zero dispersion wavelengths are both beyond 6.6 μm, thus cascaded stimulated Raman scattering is believed to be the dominant mechanism responsible for spectral broadening. With a low peak pump power of ~2.9 kW, both of the output spectra have extended to 4 μm with enhanced power distribution in the MIR region. The maximum output power of the mid-infrared supercontinua is ~140 mW. To the best of our knowledge, it is the first supercontinuum extenting to 4 μm in an As 2 S 3 fiber pumped by shortwave-infrared SC pluses in the normal dispersion region.

By pumping a 1.7-m-long As 2 S 3 fiber at 2050 nm directly, a fiber-based mid-infrared supercontinuum (SC) source with an output power of 366 mW is demonstrated. This is the first experimental demonstration to obtain such a mid-infrared SC in a piece of chalcogenide fiber pumped at 2 μm directly. The cut-off wavelength of the As 2 S 3 fiber is 3.5 μm, indicating that it could support several modes at around 2 μm. It is found that nonlinear spectral broadening mechanisms in the few-mode chalcogenide fiber could be affected through adjusting the butt-coupling position. That is because different positions will excite different modes that correspondingly possess different nonlinearity and dispersion characteristics. When stimulated Raman scattering (SRS) corresponding to the excitation of the fundamental mode becomes dominant in this few-mode fiber, an efficient cascaded SRS-based SC is obtained with five Stokes peaks ranging from 2 μm to 3.4 μm. Results from numerical simulation are in accord with the experimental results, showing that it is feasible to obtain an SRS based mid-infrared SC in a step-index As 2 S 3 fiber by using a 2 μm high peak power picosecond laser to pump directly.

Objective: We investigated whether red cell distribution width (RDW) was associated with mortality in patients with acute pancreatitis (AP)., Design: A cross-sectional study., Setting: Patients with AP were recruited in the emergency department and healthy individuals were recruited in healthcare centre in the First Affiliated Hospital of Zhejiang University., Participants: A total of 106 patients with AP and 204 healthy individuals were enrolled., Primary and Secondary Outcome Measures: Haematology and biochemistry results of the first test after admission were collected. The significance of the differences in RDW values among healthy individuals, non-survivors of patients with AP, and survivors of patients with AP was determined using one-way analysis of variance. Patients with AP were divided into three groups according to RDW tertiles. All patients with AP were followed up for at least 3 months. Receiver-operating characteristic (ROC) curve analysis and Kaplan-Meier analysis were used to evaluate RDW values to predict mortality of patients with AP., Results: The RDW values were non-survivors of patients with AP>healthy individuals>survivors of patients with AP. Patients with AP with the highest RDW tertiles had the lowest levels of Ca, total protein, albumin, haemoglobin, white and red blood cell count, but the highest mortality. The area under the ROC curve of RDW was 0.846 (95% CI 0.727 to 0.964, p<0.001). With a cut-off value of 14.2 for RDW, sensitivity and specificity of RDW to predict mortality were 75.0% and 89.8%, and Kaplan-Meier analysis showed an increase in probability of death with high RDW values., Conclusions: There is significant association between RDW and mortality of patients with AP., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.)