Forced response characteristics of random mistuned blade disk based on weibull distribution and monte carlo simulation

This paper presents a method of mistuning identification of a random mistuned bladed parameter, to predict the forced vibration characteristics of random mistuned blade disk of aeroengine compressor, based on the prestress mode synthesis method, substructure finite element reduction model was adopted, the identification method combines Weibull distribution with Monte Carlo simulation to identify the random mistuned blade parameters. The vibration characteristics of mistuned bladed disks under different engine orders of excitation were calculated, and the vibration characteristics of mistuned bladed disk systems under different mistuning standard deviations were discussed. Vibration localization characteristics of mistuned bladed disk system were analysed by using localization factor. The correctness of the identification method was verified by calculating the vibration amplitude of mistuned bladed disk system under different mistuning standard deviations

catena-Poly[[tri-n-butyl­tin(IV)]-μ-2-thio­phene­acetato]

The title compound, [Sn(C4H9)3(C6H5O2S)]n, possesses an infinite chain structure. The SnO2C3 centre has a distorted trigonal-bipyramidal geometry (τ = 0.145) with the O atoms in the axial positions. Atoms of the thio­phene group S1 and C4 are disordered over two sites The S atom and one C atom, with attached H atom, of the thiophene ring are disordered over two positions; the site occupancy factors are ca 0.7 and 0.3

2-(Ethoxy­carbon­yl)quinolinium butyl­trichlorido(quinoline-2-carboxyl­ato-κ2 N,O)stannate(IV)

In the title compound, (C12H12NO2)[Sn(C4H9)(C10H6NO2)Cl3], the Sn atom is coordinated by one O and one N atom of a quinolinium-2-carboxyl­ate anion, three Cl atoms and one butyl ligand within a distorted octa­hedron. Three C atoms of the butyl ligand are disordered and were refined using a split model; the site occupancies are 0.57 and 0.43. The NH group of the cation is involved in inter­molecular N—H⋯O hydrogen bonding

Saturation Flow Rate and Start-up Lost Time of Dual-left Lanes at Signalized Intersection in Rainy Weather Condition

AbstractThis study aims at finding out the difference of saturation flow rate and start-up lost time at dual left lanes between normal and rainy weather. It is based on the investigation of a signalized intersection in Shanghai. The result shows that compared to clear weather, saturation flow in rainy weather decreases by 3-7 percent and each lane's start-up lost time rises by 21-31 percent. However, comparing light-medium rainy weather to clear weather, the statistical difference of each of these two parameters is not significant

Soft Roof Failure Mechanism and Supporting Method for Gob-Side Entry Retaining

To study the soft roof failure mechanism and the supporting method for a gateway in a gently inclined coal seam with a dip angle of 16° kept for gob-side entry retaining, and through the methodology of field investigation and numerical and analytical modeling, this paper analyzed the stress evolution law of roof strata at the working face end and determined that the sharp horizontal stress unloading phenomenon along the coal wall side did not appear after the working face advanced. Conversely, the horizontal stress along the gob side instantly decreased and the tensile stress produced, and the vertical stress in the central part of the roof had a higher reduction magnitude as well. An in-depth study indicates that the soft roof of the working face end subsided and seriously separated due to the effect of the front abutment pressure and the roof hanging length above the gob line, as well as certain other factors, including the rapid unloading of the lateral stress, tension and shear on the lower roof rock layer and dynamic disturbance. Those influencing factors also led to rapid crack propagation on a large scale and serious fracturing in the soft roof of the working face end. However, in the gob stress stabilized zone, the soft roof in the gob-side entry retaining has a shearing failure along the filling wall inside affected by the overburden pressure, rock bulking pressure, and roof gravity. To maintain the roof integrity, decrease the roof deformation, and enable the control of the working face end soft roof and the stabilization of the gob-side entry retaining roof, this study suggests that the preferred bolt installation angle for the soft roof situation is 70° based on the rock bolt extrusion strengthening theory

Safety Situation and Policy on Mountain Highway of China

Abstract: The mountainous area approximately composes 2/3 of Chinese nation. The mountain road safety situation is important to the whole country. The paper starts from the characteristic of mountain road accidents. Through the studies the mountain road accidents shows different. There is higher death rate and more traffic accidents. In the major accidents, more accidents are fall to the roadside and the vehicles type is complex. By the actual survey in Sichuan Chongqing Yunnan and Guizhou four province, the mountain road safety facilities are checked. The characteristics and problems are found. Through the road traffic accidents analysis and the existing status of mountain safety facilities, the mountain road safety technology policies are given, which will provide a reference for managers

Vibration reduction optimization for mistuned bladed disk based on reduced order modeling technique

The arrangement optimization algorithm of blades can reduce the vibration localization of mistuned bladed disk in a compressor of aero-engine, however, it will destroy the dynamic balance of bladed disk. A new arrangement optimization method of isolation zone on bladed disk system considering unbalance moment is proposed, on the basis the reduced order modeling technology. This method is based on the finite element model and can be implemented as fast and accurate vibration reduction optimization without destroying the mass balance of the bladed disk system, the method considers both mass and stiffness mistuning. Firstly, the discrete particle swarm optimization algorithm is used to sort the mass-mistuned blades according to unbalanced moment, then, the arranged bladed disk is divided into 6 isolation zones, then, in each isolation zone, the stiffness mistuned bladed disk is arranged optimally by the stiffness mistuning optimization algorithm. Under the premise of satisfying the dynamic balance of bladed disk, this algorithm optimizes the arrangement of blades with mass mistuning and stiffness mistuning, and achieves the purpose of vibration reduction optimization of mistuned bladed disk. The results show that, the maximum amplitude of the bladed disk system is reduced by 23.9 %. The vibration localization degree of the optimized blade are reduced by 46.3 %

Biophysics at the coffee shop: lessons learned working with George Oster

Over the past 50 years, the use of mathematical models, derived from physical reasoning, to describe molecular and cellular systems has evolved from an art of the few to a cornerstone of biological inquiry. George Oster stood out as a pioneer of this paradigm shift from descriptive to quantitative biology not only through his numerous research accomplishments, but also through the many students and postdocs he mentored over his long career. Those of us fortunate enough to have worked with George agree that his sharp intellect, physical intuition and passion for scientific inquiry not only inspired us as scientists but also greatly influenced the way we conduct research. We would like to share a few important lessons we learned from George in honor of his memory and with the hope that they may inspire future generations of scientists.Comment: 22 pages, 3 figures, accepted in Molecular Biology of the Cel