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Dynamic Simulations of Post-stall Performance in Multistage Axial Compressors

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Journal of Thermal Science 2012年第4期21卷 311-321页

作者： DU Wenhai ZHU JunQiang Olivier Leonard University of Liege Turbomachinery Group B-4000 Liege Belgium Institute of Engineering Thermophysics ChineseAcademy of Sciences China Chinese Academy of Sciences China University of Liege Turbomachinery Group chemin des chevreuils 1 B-4000 Liege Belgium

In this contribution a quasi-one-dimensional tool for stationary and transient simulations of post-stall flows in multistage axial compressors is presented. An adapted version of the 1D Euler equations with additional source terms is discretized with a finite volume method and solved in time by a fourth-order Runge-Kutta scheme. The equations are discretized at midspan both inside the blade rows and the non-bladed regions. The source terms express the blade-flow interactions and are estimated by calculating the velocity triangles for each blade row. Loss and deviation correlations are implemented and compared to experimental data in normal flow, stalled flow and reversed flow regions. Transient simulations are carried out and a parameter study is presented to analyze the shape of the surge cycles and the frequency of the surge oscillations. At last, a bleeding control strategy is implemented to study the recoverability of the instabilities in a compression system.

关键词： surge axial compressor dynamic simulation quasi-one-dimensional model bleeding control

Experimental investigation of flow pattern and sediment deposition in rectangular shallow reservoirs

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International Journal of Sediment Research 2010年第3期25卷 258-270页

作者： Matthieu DUFRESNE Benjamin J. DEWALS Sébastien ERPICUM Pierre ARCHAMBEAU Michel PIROTTON University of Liège (ULg) ArGEnCO department MS2F sector Hydrology applied hydrodynamics and hydraulic constructions (HACH) Chemin des chevreuils 1 bat B52/3 étage +1 4000 Liège Belgium University of Liège (ULg) ArGEnCO department MS2F sector Hydrology applied hydrodynamics and hydraulic constructions (HACH) Chemin des chevreuils 1 bat B52/3 étage +1 4000 Liège Belgium.

This paper reports the experimental investigation of flow pattern, preferential regions of deposition and trap efficiency as a function of the length of rectangular shallow reservoirs. Four flow patterns were identified (from longer to shorter reservoirs): an asymmetric flow with two reattachment points, an asymmetric flow with one reattachment point, an unstable flow, and a symmetric flow without any reattachment point. Using dye visualizations, the median value and the temporal variability of the reattachment lengths were precisely measured for the asymmetric flows. For each stable flow, sediment tests with plastic particles were carried out. The regions of deposition on the bed of the reservoir were clearly a function of the flow pattern. The transition from an asymmetric flow pattern to a symmetric flow pattern was responsible for an abrupt decrease of the trap efficiency; a number of regression laws were discussed to take it into account.

关键词： Deposition Flow patterns Reservoirs Sediment Shallow water

Large endoscopic mucosal resection for colorectal tumors exceeding 4 cm

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World Journal of Gastroenterology 2010年第5期16卷 588-595页

作者： Philippe Ah Soune Charles Ménard Ezzedine Salah Ariadne desjeux Jean-Charles Grimaud Marc Barthet Department of Gastroenterology Hpital NordChemin des Bourrely13915 Marseille cedex 20France

AIM:To evaluate the feasibility and the outcome of endoscopic mucosal resection(EMR)for large colorectal tumors exceeding 4 cm(LCRT)undergoing piecemeal resection. METHODS:From January 2005 to April 2008,146 digestive tumors larger than 2 cm were removed with the EMR technique in our *** these,34 tumors were larger than 4 cm and piecemeal resection was carried out on 26 colorectal *** mean age of the patients was 71 *** mean follow-up duration was 12 mo. RESULTS:LCRTs were located in the rectum,left colon,transverse colon and right colon in 58%,15%, 4%and 23%of cases,*** were sessile tumors larger than 4 cm with a mean size of 4.9 cm (4-10 cm).According to the Paris classification,34%of the tumors were typeⅠs,58%typeⅡa,4%typeⅡb and 4%typeⅡ*** examination showed tubulous adenoma in 31%,tubulo-villous adenoma in 27%,villous adenoma in 42%,high-grade dysplasia in38%,in situ carcinoma in 19%of the cases and mucosal carcinoma(m2)in 8%of the *** two cases(7.7%)of procedural bleeding that occurred were managed endoscopically and one small perforation was treated with *** follow-up,recurrence of the tumor occurred in three patients(12%),three of whom received endoscopic treatment. CONCLUSION:EMR for tumors larger than 4 cm is a safe and effective procedure that could compete with endoscopic submucosal dissection,despite providing incomplete histological assessment.

关键词： Endoscopic mucosal resection Perforation Colorectal carcinoma Large polyps

Medical treatment for sphincter of oddi dysfunction:Can it replace endoscopic sphincterotomy?

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World Journal of Gastroenterology 2012年第14期18卷 1610-1615页

作者： Véronique Vitton Salah Ezzedine Jean-Michel Gonzalez Mohamed Gasmi Jean-Charles Grimaud Marc Barthet Department of Gastroenterology Hôpital NordChemin des Bourrely13915 Marseille cedex 20France

AIM:To report the results of a medical management of sphincter of oddi dysfunction(SOD) after an intermediate follow-up ***:A total of 59 patients with SOD(2 men and 57 women,mean age 51 years old) were included in this prospective *** medical treatment for one year,the patients were clinically re-evaluated after an average period of 30 ***:The distribution of the patients according to the Milwaukee's classification was the following:11 patients were type 1,34 were type 2 and 14 were type *** patients underwent an endoscopic sphincterotomy(ES) after one year of medical *** median intermediate follow-up period was 29.8 ± 3 mo(3-72 mo).The initial effectiveness of the medical treatment was complete,partial and poor among 50.8%,13.5% and 35%,respectively,of the *** the end of the follow-up period,37 patients(62.7%) showed more than 50% *** rate of improvement in patients who required ES was not significantly different compared with the patients treated conservatively(64.2% vs 62.2%,respectively).CONCLUSION:Our study confirms that conservative medical treatment could be an alternative to endoscopic sphincterotomy because,after an intermediate follow-up period,the two treatments show the same success rates.

关键词： Sphincter of oddi dysfunction Cholecystectomy Endoscopic sphincterotomy Biliary scintigraphy

Rescuing the intracluster medium of NGC 5813

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Research in Astronomy and Astrophysics 2016年第6期16卷 139-144页

作者： Noam Soker Shlomi Hillel Assaf Sternberg Department of Physics Technion–Israel Institute of Technology Geneva Observatory University of GenevaChemin des Maillettes 51

We use recent X-ray observations of the intracluster medium （ICM） of the galaxy group NGC 5813 to confront theoretical studies of ICM thermal evolution with the newly derived ICM prop- erties. We argue that the ICM of the cooling flow in the galaxy group NGC 5813 is more likely to be heated by mixing of post-shock gas from jets residing in hot bubbles with the ICM, than by shocks or turbulent- heating. Shocks thermalize only a small fraction of their energy in the inner regions of the cooling flow; in order to adequately heat the inner part of the ICM, they would overheat the outer regions by a large factor, leading to its ejection from the group. Heating by mixing, which was found to be much more efficient than turbulent-heating and shocks-heating, hence, rescues the outer ICM of NGC 5813 from its predestined fate according to cooling flow feedback scenarios that are based on heating by shocks.

关键词： galaxies: active -- galaxies: clusters: general -- galaxies: groups: individual (NGC 5813) --galaxies: jets

Transparent conducting materials discovery using high-throughput computing

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npj Computational Materials 2019年第1期5卷 606-618页

作者： Guillaume Brunin Francesco Ricci Viet-Anh Ha Gian-Marco Rignanese Geoffroy Hautier UCLouvain Institut de la Matière Condensée et des Nanosciences(IMCN)Chemin desÉtoiles 8Louvain-la-Neuve 1348Belgium

Transparent conducting materials(TCMs)are required in many applications from solar cells to transparent *** high performance materials combining the antagonistic properties of transparency and conductivity has been challenging especially for p-type ***,high-throughput ab initio computational screening has emerged as a formidable tool for accelerating materials *** this review,we discuss how this approach has been applied for identifying *** provide a brief overview of the different materials properties of importance for TCMs(e.g.,dopability,effective mass,and transparency)and present the ab initio techniques available to assess *** focus on the accuracy of the methodologies as well as their suitability for high-throughput ***,we review the different high-throughput computational studies searching for new TCMs and discuss their differences in terms of methodologies and main findings.

关键词： transparency conducting suitability

Updated EAS and SRI Finite Element Formalism for Thermomechanical Modeling at Finite Strains

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Updated EAS and SRI Finite Element Formalism for Thermomecha...

Mechanical Buckling Analysis of Composite Panels with/without Cutouts

The Sixth World Congress on Computational Mechanics in Conjunction with the Second Asian-Pacific Congress on Computational MechanicsⅠ

作者： Laurent Adam Jean-Philippe Ponthot Department of Aeronautics University of Liege B52/3 chemin des chevreuils 1 B4000 Liege Belgium Department of Aeronautics University of Liege B52/3 chemin des chevreuils 1 B4000 Liege Belgium

Classical first order finite elements are well known to exhibit locking(both in shear and over the volumetric deformation) when integrated exactly. One of the most used finite element techniques to removed locking is the SRI(Selective Reduced Integration). However this technique is usually applied to remove the volumetric locking only. Reduced Integration(RI) technique used to remove all types of locking has the drawback of developing hourglassing mesh instabilities. EAS(Enhanced Assumed Strains) formalism enables us to have a locking-free response with weaker mesh instabilities. In this updated enhanced Lagrangian framework, hourglassing hardly appears. Thus there is no major need to use higher order spatial integration rules or stabilization techniques. The aim of this paper is to describe an updated EAS finite element formalism used to model the thermomechanical behavior of metal during processes such as sheet forming or impact. The features of this formalism used jointly with and updated Lagrangian approach and a hyperelastic anisothermal constitutive formulation will be described.

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International Journal of Plant Engineering and Management 2012年第2期17卷 65-76页

作者： Oana Zenaida PASCAN ZHANG Wei-hong Jean Philippe PONTHOT Department of Aerospace and Mechanical Engineering University of Liege Chemin des Chevreuils 1 B-4000 LIEGE 1 BELGIUM Engmeenng Simulation and Aerospace Computing Northwestern Polytechnical University Xi'an 710072

A simplified analytical solution suitable for simple stacking sequences was developed using the Euler buck- ling theory, the structure＇s equations of equilibrium and laminate panel mathematical formulation. Comparing these results with numerical results reveals the accuracy of the method and even more, allows us to validate the nu- merical analysis. Therefore, two important results are obtained： a simplified analytical solution for the buckling problem and validation of the numerical results. Another important and novel finding is related to the influence of the angle ply orientation and of the cutouts, on the buckling load. Under symmetrical boundary conditions and loading case, rectangular panels with elliptical cutouts, give better results for 90~ oriented plies than for 0 oriented ones. With a compression load applied in the X direction, and with material properties 10 times better in X direction than in Y direction, the best results are obtained when the load is aligned with the Y direction associated to the ma- terial reference frame. Moreover, panels with cutouts seem to behave better than panels without cutouts under cer- tainply orientation angles.

关键词： linear buckling analytical solution mechanical loading angle ply orientation cutouts

Numerical Investigation of Flutter Stability in Subsonic Space Turbine Blisk with Emphasis on Cut-on/Cut-off Modes and Interblade Phase Angles

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Journal of Thermal Science 2012年第6期21卷 492-499页

作者： Hakim Ferria Pascal Ferrand Franois Pacull Stéphane Aubert Laboratoire de Mécanique des Fluides et d'Acoustique CNRS UMR 5509 Université de LyonUniversité Claude Bernard Lyon 1INSA Lyon 36avenue Guy de Collongue69134 EcullyFrance Fluorem 64 chemin des Mouilles69134 EcullyFrance

The so-called blisks,*** bladed disks,are characterized by very low viscous material damping and make the flutter prediction much more *** that framework,a two-dimensional numerical study of a space turbine blisk featuring complex deformation of blades and high eigenfrequency(>40kHz)is *** simulations are based on unsteady Reynolds Averaged Navier Stokes computations linearized in the frequency domain and consist in the superposition of an unsteady linear(in time)pressure field,generated by a harmonic perturbation,upon a steady nonlinear(in space)*** aerodynamic damping coefficient is calculated over a range of nodal diameters,and the blades are predicted aeroelastically ***,violent changes occur and are rather critical since sudden and large deviations in stability *** that context,the nature of the waves propagating from the cascade are *** an approach provides fundamental knowledge about the perturbations which can either propagate to the far-field(cut-on mode)or decay(cut-off mode).It is expected that the ability of the flow to damp or to amplify the blade motion is strongly affected by the way unsteady perturbations are transferred from the cascade to the *** nature of the waves are first assessed from the aforementioned linearized results,then they are evaluated analytically and finally compared.A good agreement is found despite the strong assumptions of the analytical *** results show a clear correlation between the cut-on/cut-off conditions and *** least stable configuration corresponds to cut-off mode at the inlet and no wave at the *** outgoing waves from the cascade,the blade is prone to be less stable:the energy from the blades vibration is necessarily dissipated or sent out by the cascade.

关键词： subsonic flutter LRANS blisk cut-on/cut-off mode interblade phase angle nodal diameter.