In this study, we first observed second-order primary rogue waves in solids by experiments using a modal based on waves. We found that the propagation of can be described nonlinear Schrödinger equation. To enhance our understanding, employed variational mode decomposition and identified inherent frequency as main factor. Therefore, conducted spectral analysis to determine discussed results. The theoretical experimental results are agreement, findings applied non destructive testing large...

Abstract Clinical studies report significant increases in acrolein (an α,β-unsaturated aldehyde) the substantia nigra (SN) of patients with Parkinson’s disease (PD). In present study, acrolein-induced neurotoxicity nigrostriatal dopaminergic system was investigated by local infusion (15, 50, 150 nmoles/0.5 μl) SN Sprague-Dawley rats. Acrolein-induced neurodegeneration delineated reductions tyrosine hydroxylase (TH) levels, dopamine transporter levels and TH-positive neurons infused as well...

Abstract The shaft mechanical face seal in a high-speed turbopump of liquid rocket engine often operates under extremely harsh conditions. For example, low-temperature and low-viscosity fluid (such as oxygen or hydrogen) is used lubricant. performance the rings, especially friction wear behavior, directly determines whether functions normal. In this study, behavior several ring materials are tested using pin-on-disk tribo-tester, morphology investigated. coefficients (COFs) mass-wear rates...

As the main disease of railway tunnels, void affects safe operation railways. The traditional detection technology recognition relies on intuitive characteristics signal, there are still problems such as poor edge capability and low intelligence level. To solve this problem, study used Comsol software to establish a sound-solid coupling finite element model tunnel, extracted acoustic signals voids under various conditions, analysed signal different conditions proposed sensitive frequency...

The spiral-grooved seal is a prime candidate for application to liquid oxygen (LOX) turbopumps. A theoretical model of double spiral–grooved seals dealing with the viscosity–temperature relation presented. effect operating parameters (rotational speed, supply pressure) and configurative (depth spiral groove) on basic static characteristics (opening force, leakage, friction torque, face temperature, power loss) are examined. Comparisons presented between measurements predications narrow an...

Abstract The friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester, the GCr15–graphite seal pairs low-temperature time-dependent pretreatment was discussed comparing morphology. results show that can affect hardness interlayer spacing graphite. range coefficients changes from 0.17 to 0.22. With increase time, mechanism would change dominated three-body adhesion wear. experimental mechanical stator is less than 0.00165 mm 3...

An experimental test system for cryogenic high-speed hydrodynamic non-contact mechanical seals is developed. Based on this system, the performances of under different working conditions are studied in detail paper. With results, main (such as inlet and outlet temperatures, separated speed, face temperature, friction force, coefficient, leakage rate) obtained, relationships with fluid pressure, closing force rotational speed discussed. The results show that difference between temperatures...

Purpose – A new type of hydrostatic and hydrodynamic non-contacting face seals has been designed to meet the requirements lower leakage, longer life more repeatedly start stop on shaft raised by liquid rocket engine turbopumps. And an experimental study performance seal in actual oxygen turbopump was completed where low-viscosity water selected as fluid for sake safety. The paper aims discuss these issues. Design/methodology/approach Different performances under preset conditions were...

Since the disadvantages of a lot calculation for traditional SVPWM algorithm in three-level neutral-point -clamped (NPC) inverter, which is not easy to real-time control,a space vector PWM (SVPWM) based on 60° coordinate system proposed. The coordinates are integeres by simple transformation, and basic vectors achieved reference upward rounded down respectively, whose effective time calculated principle Volt-seconds balance. switching state equation introduced control voltage balance...

Purpose The serious friction and wear problem occurs on the mechanical seal’s faces during start-up stage of high-speed turbopump for a liquid rocket engine. This paper aims to propose kind thick metal alloy coatings surface rotor so as reduce wear. Design/methodology/approach With pin-disk (the graphite pin disk with coating) tribology-tester, tribological behaviors four are investigated. special coefficients under dry friction, boundary different temperatures water-lubricated conditions...

Feature extraction is the key for detecting and identifying subgrade shallow targets of railways through ground-penetrating radar (GPR). Obtaining appropriate feature to recognize subsurface difficult due complication structures diversity target echoes. To identify those effectively efficiently, this study proposes an energy statistical method based on directional a echo. Directional models typical echo were initially built. The different echoes was discussed. direction hyperbolic asymptote...

摘要: 液体火箭发动机高速涡轮泵的起动是在高压、低温等极端工况下的典型瞬态起动,极易导致其支承轴承的失效。本文构建了低温滚动轴承全液膜润滑和起动摩擦力矩的求解模型,获得了在特定工况下不同滚动体位置的液膜压力分布和最小液膜厚度等;计算得到了起动过程不同载荷和转速下特定低温轴承的起动摩擦力矩,并以此提出了确保轴承瞬态安全起动的最小径向预载方法。开展了液氮工况下的两组快速起动低温滚动轴承的试验测试,获得了高速起动下轴承的动态响应特征,其结果定性地验证了最小径向预载定义方法的合理性;动态响应的快速特征提取也表明了轴承在起动阶段的失效可能为局部碰磨,甚至存在不同轴承组件间严重的金属摩擦或者刮擦。研究结果对于提高低温液体火箭发动机高速涡轮泵的安全服役性能具有重要的理论和试验价值。

The inseparability criterion provides a straightforward and efficient method for identifying quantifying two-mode Gaussian quantum entanglement, making it crucial tool in optics experiments. However, is to recognize that the serves only as sufficient condition entanglement assessment, thereby posing risk of missed detection during evaluation. This paper investigates use assessing squeezed states, with particular focus on examining due asymmetry. results show when decoherence symmetrically...

Motor parameter identification is problem must be faced by high performance variable frequency speed adjustment system include Vector Control. Explore new effective method possess vast theoretical and practical meanings. Motor's mathematical model has the character of order, nonlinear complicate coupling, change with work state difficult to describe a definite function. Rotor resistance identified Elman neural network which ability function approximation unique feedback. The simulation...