Remaining Useful Life Prediction for Aero-Engines Combining Sate Space Model and KF Algorithm

The key to failure prevention for aero-engine lies in performance prediction and the exhaust gas temperature margin(EGTM)is used as the most important degradation parameter to obtain the operating performance of the aero-engine.Because of the complex environment interference,EGTM always has strong randomness,and the state space based degradation model can identify the noisy observation from the true degradation state,which is more close to the actual situations.Therefore,a state space model based on EGTM is established to describe the degradation path and predict the remaining useful life(RUL).As one of the most effective methods for both linear state estimation and parameter estimation,Kalman filter(KF)is applied.Firstly,with EGTM degradation data,state space model approach is used to set up a state space model for aero-engine.Secondly,RUL of aero-engine is analyzed,and expected RUL and distribution of RUL are determined.Finally,the sate space model and KF algorithm are applied to an example of CFM-56aero-engine.The expected RUL is predicted,and corresponding probability density distribution(PDF)and cumulative distribution function(CDF)are given.The result indicates that the accuracy of RUL prediction reaches 7.76%ahead 580 flight cycles(FC),which is more accurate than linear regression,and therefore shows the validity and rationality of the proposed method.

PRINCIPLES OF EFFECTIVE SELECTION AND THEIR APPLICATION WANG Bo

Successful selection principles and their application in China are discussed. In addition, the selection process of two Chinese Joint Ventures is reviewed. The paper emphasizes the importance of conducting structured job relevant, behaviour or situation based interviews, with pre determined guideline answers and examples provided. The research showing the increased predictive validity of using this type of interview format is presented. The types of outcomes sought by Canadian employers and the attributes employees or agents should possess are provided. It is argued that these should serve as the basis for creating the interview format. The use of testing and reference checks is also discussed.

Models for depression in drug screening and preclinical studies:Future directions

The basic consideration in the feld of antidepressants is that tests to model depression do not exist, as de-pression etiopathology is unknown. So far, any kind of proposed model for depression needs to satisfy construct, face and predictive validities. In the present editorial, this idea is challenged, based on the fact that “old” methods can only reveal therapeutical “me-too” drugs and that there is no longer a need of therapeu-tical “me-too” drugs in the field of antidepressants. Since reduction in the number of antidepressant non-responders is a real medical need, the predictive valid-ity of animal models will be challenged in the future, as the new methods should be based on antidepressant-insensitive animals. Moreover, antidepressants exert similar effects in depressed and non-depressed sub-jects, but mood normalization is only induced in de-pressed patients. This implies that the use of normal cells and animals only involves pharmacological rather than therapeutical actions of drugs. Therefore, the use of environmental-induced changes, in the hope that these can evidence antidepressant-insensitive animals, will predominantly be used in the future. In the choice of experimental settings, other factors need to be taken into consideration： （1） gender of animals, as de-pression affects females more than males, （2） natural rhythmicity in drug effects; （3） pharmacokinetics; and （4） possible biomarker（s） to be measured. There are no golden recipes to discover new antidepressants but the experimental long-term strategy should very clearly be declared before starting the experiments.

A Critical Review on IELTS Writing Test of Academic Module

The International English Language Testing System(IELTS) is one of the most widely used language proficiency test inthe world. In the IELTS academic module, the writing test is a significant part to assess examinees' writing ability on the ground ofthe university academic level. Since the IELTS academic writing test measures test-takers' academic writing competency and pre-pares them for the university study, it is necessary to figure out the extent this test could be beneficial to test-takers for future uni-versity learning. This paper aims to provide a critical review of the IELTS writing test, dawning on"principles of test assessment"introduced by Brown and Abeywickrama(2010), and focusing particularly on the predictive validity, authenticity, and washback.

Development and validation of a radiomics nomogram for preoperative prediction of lymph node metastasis in colorectal cancer

With the support by the National Natural Science Foundation of China,the research team jointly led by Porf.Liu Zaiyi(刘再毅)at Guangdong General Hospital and Prof.Tian Jie(田捷)at the Key Laboratory of Molecular Imaging,Chinese Academy of Sciences,developed a CT-based radiomics prediction model to preoperatively predict the lymph node metastasis in colorectal cancer(CRC),which was published

Prediction of oil-water flow patterns, radial distribution of volume fraction, pressure and velocity during separated flows in horizontal pipe

Flow of two immiscible fluids gives rise to variety of flow patterns,which influence transportation process.In this work,we present detailed analysis on the prediction of flow pattern maps and radial distribution of volume fraction,pressure and velocity of a pair of immiscible liquids through a horizontal pipeline by computational fluid dynamics（CFD） simulation using ANSYS FLUENT 6.3.Moderately viscous oil and water have been taken as the fluid pair for study.Volume of fluid（VOF） method has been employed to predict various flow patterns by assuming unsteady flow,immiscible liquid pair,constant liquid properties,and co-axial flow.From the grid independent study,we have selected 47 037 number of quadrilateral mesh elements for the entire geometry.Simulation successfully predicts almost all the flow patterns（viz.,plug,slug,stratified wavy,stratified mixed and annular）,except dispersion of oil in water and dispersion of water in oil.The simulated results are validated with experimental results of oil volume fraction and flow pattern map.Radial distribution of volume fraction,pressure and velocity profiles describe the nature of the stratified wavy,stratified mixed and annular flow pattern.These profiles help to developing the phenomenological correlations of interfacial characteristics in two-phase flow.

Prediction and validation of tonal noise from underwater propellers

Prediction and validation of low-frequency line spectrum noise from ship propeller under non-cavitating condition is presented.The flow field is analyzed with potential-based panel method,which requires the hydrodynamic forces to be integrated over the actual blade surface,rather than over the mean-chord surface.Then the pressure data is used as the input for Ffowcs Williams-Hawkings formulation to predict the far field acoustics.At the same time,propeller unsteady force is measured in hull-behind condition in China Large Cavitation Channel（CLCC）.Line spectrum noise of the 1st blade passage frequency（BPF） of a five-bladed propeller operating in a non-uniform flow field is got according to the calculated and measured unsteady forces,in which good agreement is obtained,and the 1st BPF noise difference is within 3.0 dB.The investigation reveals that prediction precision of the propeller＇s 1st BPF unsteady force with panel method have reached engineering practical degree,providing significant parameters for prediction of propeller line spectrum noise.