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Acoustic instabilities in solid rocket motors (SRMs) can lead to severe performance deterioration and structural damage. Nozzle damping accounts for the main acoustic dissipation source, and it is highly dependent on geometric parameters and operating conditions. This study experimentally investigated the acoustic damping characteristics of submerged nozzles in SRMs, focusing on the effects of submerged cavity dimensions, nozzle convergent angle, throat-to-port area ratio, and mean pressure variations on the longitudinal instability. The steady-state wave decay method was used to quantify the acoustic damping, and a designed rotary valve system was employed to introduce periodic pressure oscillations in the high-pressure combustion chamber. The results revealed that a larger submerged cavity would reduce the nozzle damping efficiency, with the elimination of the submerged cavity enhancing the nozzle decay coefficient magnitude by 41.9%. Furthermore, increasing the nozzle convergent angle was found to amplify acoustic wave reflection, thereby diminishing damping performance. A linear inverse relationship was observed between the throat-to-port area ratio and the decay coefficient, with a 125% increase in the ratio resulting in a 24.3% reduction in the decay coefficient. Interestingly, despite the formation of complex vortices in the submerged cavity, the mean pressure variation presented negligible effects on acoustic damping characteristics, and its damping performance is similar to a simple nozzle without a cavity. These findings provide valuable experimental data for predicting the stability of a solid rocket motor with a submerged nozzle and offer insights into the optimization of submerged nozzle designs for higher acoustic damping in SRMs. [ABSTRACT FROM AUTHOR]

The rectangular pipe jacking method is an efficient, green, trenchless technology for constructing urban underground space. However, some problems, including the high jacking resistance, the instability of the tunneling face, and excessive ground settlement during the large-section rectangular pipe jacking for the underpass of national highways, seriously affect construction safety and traffic. Based on the engineering background of the large-section rectangular pipe jacking in constructing the subway entrance tunnel of Guangzhou Metro Line 7, this work adopts the methods of theoretical calculation, numerical simulation, and engineering application. Five kinds of mechanical models for pipe soil slurry interactions in rectangular pipe jacking are analyzed. An evaluation of the applicability of the jacking force prediction of the different models is conducted. Moreover, the ground settlement law for the large-section rectangular pipe jacking for the underpass of national highways under different influencing factors, including slurry sleeve thickness, grouting pressure, and earth chamber pressure, is revealed. The control countermeasures of the ground settlements, such as installing a waterproof rubber curtain for the tunnel portal, pipe jacking machine receiving techniques, thixotropic slurry for reducing friction resistance, and soil stability at the tunneling face, are carried out. The results show that there is no need to install an intermediate jacking station in the large-section rectangular pipe jacking project with a jacking distance of 63 m. The most reasonable thickness of the thixotropic slurry sleeve is about 150 mm. The most reasonable grouting pressure range is 600–700 kPa. An earth chamber pressure of about 153 kPa is more reasonable to control the soil stability of the tunneling face. The engineering practice shows that the maximum ground settlement of the national highway during jacking is 10 mm. The maintenance effect is excellent, and the traffic operates normally. [ABSTRACT FROM AUTHOR]

Background: Many observational epidemiology studies discovered that kidney cancer and impaired kidney function have a bidirectional relationship. However, it remains unclear whether these two kinds of traits are causally linked. In this study, we aimed to investigate the bidirectional causal relation between kidney cancer and kidney function biomarkers (creatinine‐based estimated glomerular filtration rate (eGFRcrea), cystatin C‐based estimated glomerular filtration rate (eGFRcys), blood urea nitrogen (BUN), serum urate, and urinary albumin‐to‐creatinine ratio (UACR)). Methods: For both directions, single‐nucleotide polymorphisms (SNPs), as genetic instruments, for the five kidney function traits were selected from up to 1,004,040 individuals, and SNPs for kidney cancer were from 408,786 participants(1338 cases). In the main analysis, we applied two state‐of‐the‐art MR methods, namely, contamination mixture and Robust Adjusted Profile Score to downweight the effect of weak instrument bias, pleiotropy, and extreme outliers. We additionally conducted traditional MR analyses as sensitivity analyses. Summary‐level data of European ancestry were extracted from UK Biobank, Chronic Kidney Disease Genetics Consortium, and Kaiser Permanente. Results: Based on 99 SNPs, we found that the eGFRcrea had a significant negative causal effect on the risk of kidney cancer (OR = 0.007, 95% CI:2.6 × 10−4–0.569, p = 0.041). After adjusting for body composition or diabetes, urate had a significant negative causal effect on kidney cancer (OR <1, p < 0.05). For UACR, it showed a strong causal effect on kidney cancer, after adjusting for body composition (OR = 14.503, 95% CI: 2.546–96.001, p = 0.032). Due to lacking significant signals and effect power for the reverse MR, further investigations are warranted. Conclusions: Our study suggested a potential causal effect of damaged kidney function on kidney cancer. EGFRcrea and UACR might be causally associated with kidney cancer, especially when patients were comorbid with obesity or diabetes. We called for larger sample‐size studies to further unravel the underlying causal relationship and the exact mechanism. [ABSTRACT FROM AUTHOR]

An experimental model for heart-mural coronary artery-myocardial bridge was established based on the theory of haemodynamics. The application of the model demonstrated that it can repeat to great extent the phenomenon of the myocardial bridge compressing the mural coronary artery, which results in abnormal haemodynamic characteristics. The results of simulation experiments are mostly consistent with clinical research. [ABSTRACT FROM AUTHOR]

Abstract: In order to create a hemodynamic environment that can simulate the physiological condition of arteries, an in vitro experiment apparatus was designed whose key modules were compliance chamber and after-load. These two modules were developed based on the theories of hemodynamics. Both the normal and shear stress to which endothelial cells are exposed can be controlled with these modules, thus facilitating the research of endothelial cells subjected to stresses. [Copyright &y& Elsevier]

A protective device was designed that can be worn on the elderly, which consists of protective airbag, control box and protective mechanism. The combined acceleration, combined angular velocity and human posture angle are selected as the parameters to determine the fall, and the threshold algorithm and SVM algorithm are used to detect the fall. The protective mechanism is an inflatable device based on CO 2 compressed air cylinder, and the equal-width cam structure is applied to its transmission part to improve the puncture efficiency of the compressed gas cylinder. A fall experiment was designed to obtain the combined acceleration and angular velocity eigenvalues of fall actions (forward fall, backward fall and lateral fall) and daily activities (sitting-standing, walking, jogging and walking up and down stairs), showing that the specificity and sensitivity of the protection module reached 92.1% and 84.4% respectively, which verified the feasibility of the fall protection device.

Medical nitric oxide(NO)flow control system plays an important role in lowering pulmonary hypertension.The design requirements,overall scheme,delivery system and hardware circuits of a medical NO flow control system were introduced in this paper.Particularly,we proposed the design of NO delivery system and hardware circuits in detail.To deliver nitric oxide of a variable concentration,the designed system needs to work with a ventilator.The system can adjust and monitor the inhaled nitric oxide concentrations and send out sound and light alarms when the inhaled nitric oxide concentrations are out of the set range.To validate reliability and efficacy,we measured specifications such as linearity,stability and response time of the proposed NO flow control system by continuously administering nitric oxide into inspiratory circuit to deliver nitric oxide of variable concentrations to a test lung.The experiments showed that these specifications can meet the desired requirements.

According to the clinical requirements of cardiopulmonary bypass surgery, this paper established a simulation system for cardiac surgery which consists of venous reservoir, variable balance chamber, blood suction bag, ventricle suction bag, resistance valves, pressure gauges and tubings. Using the proposed system, perfusionists can mimic the implementation of pre-established surgery strategy, predict various abnormal conditions in the operation, and accordingly take the urgent actions so as to improve the success rate of surgery and to ensure the safety of patients.

This paper mainly studies the driving system of centrifugal blood pump for extracorporeal circulation, with the core being disc magnetic coupling. Structure parameters of disc magnetic coupling are related to the ability of transferring magnetic torque. Therefore, it is necessary to carry out disc magnetic coupling permanent magnet pole number (n), air gap length (L(g)), permanent magnet thickness (L(m)), permanent magnet body inside diameter (R(i)) and outside diameter (R(o)), etc. thoroughly. This paper adopts the three-dimensional static magnetic field edge element method of Ansys for numerical calculation, and analyses the relations of magnetic coupling each parameter to transmission magnetic torque. It provides a good theory basis and calculation method for further optimization of the disc magnetic coupling.

Using extracorporeal circulation for cardiopulmonary bypass is the first step for the successful cardiac surgery, and the blood pump is the key component in extracorporeal circulation devices, the control and measurement of mechanical-fluid parameters such as flow rate and pressure are very important to guarantee the successful cardiac surgery. This paper reviews several control methods of the blood pump based on the flow rate/pressure, heart rate, ventricular work and blood assist index, and also discusses the direct and indirect measurements of the flow rate and pressure. This review concludes with the main possible trends for the further development of the blood pump control and testing methods.

This paper is aimed to study the optimal selection of structure of vaneless centrifugal blood pump. The optimal objective is determined according to requirements of clinical use. Possible schemes are generally worked out based on structural feature of vaneless centrifugal blood pump. The optimal structure is selected from possible schemes with constraints on blood perfusion and blood damage indexes. Using an optimal selection method one can find the optimum structure scheme from possible schemes effectively. The results of numerical simulation of optimal blood pump showed that the method of constraints of blood perfusion and blood damage is competent for the requirements of selection of the optimal blood pumps.

A problem of temperature distortion of medical thermography of the limb ending which results from different infrared radiant intensity of points detected by infrared detector was discussed. Further the difference of the radiant intensity is caused by that of projecting angles of points. Subsequently through related theory and experiments this paper found that the temperature shown by thermography bears a Gauss attenuation relation to actual surface temperature of an object. A Gaussian Matching Arithmetic was put forward to correct this kind of temperature distion. Finally, by using this Arithmetic a temperature distortion of thermography of a finger was corrected and the results were exciting.