http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Strain conservation in implantation-doped GeSi layers on Si (100)
Nicolet, M A,Im, S 대한금속재료학회(대한금속학회) 1997 METALS AND MATERIALS International Vol.3 No.2
Metastable pseudomorphic GeSi layers grown by chemical vapor deposition or by molecular beam epitaxy on Si(100) substrates were implanted at room temperature. The implantations were performed with 90 keV As ions to a dose of 1×10^(13) ㎝^(-2) for Ge_(0.08)Si_(0.92) layers and 70 keV BF₂^+ ions to a dose of 3×10^(13) ㎝^(-2) for Ge_(0.06)Si_(0.94) layers. The samples were subsequently annealed for short 10-40 s durations in a lamp furnace with a nitrogen ambient, or for a long 30 min period in a vacuum tube furnace. For Ge_(0.08)Si_(0.92) samples annealed for a 30 min-long duration at 700℃, the dopant activation can only reach 50% without introducing significant strain relaxation, whereas samples annealed for short 40 s periods (at 850℃) can achieve more than 90% activation without a loss of strain. For Ge_(0.06)Si_(0.94) samples annealed for either 40 s or 30 min at 800℃, full electrical activation of the boron is exhibited in the GeSi epilayer without losing their strain. However, when annealed at 900℃, the strain in both implanted and unimplanted layers is partly relaxed after 30 min, whereas it is not visibly relaxed after 40 s.
Nicolet, Christophe,Alligne, Sebastien,Kawkabani, Basile,Simond, Jean-Jacques,Avellan, Francois Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.4
This paper presents a numerical simulation study of the transient behavior of a $2{\times}340MW$ pump-turbine power plant, where the results show an unstable behavior at runaway. First, the modeling of hydraulic components based on equivalent schemes is presented. Then, the 2 pump-turbine test case is presented. The transient behavior of the power plant is simulated for a case of emergency shutdown with servomotor failure on Unit 1. Unstable operation at runaway with a period of 15 seconds is properly simulated using a 1-dimensional approach. The simulation results points out a switch after 200 seconds of the unstable behavior between a period of oscillations initially of 15 seconds to a period of oscillation of 2.16 seconds corresponding to the hydraulic circuit first natural period. The pressure fluctuations related to both the rigid and elastic water column mode are presented for oscillation mode characterization. This phenomenon is described as a switch between a rigid and an elastic water column oscillation mode. The influence of the rotating inertia on the switch phenomenon is investigated through a parametric study.
Nicolet, Christophe,Zobeiri, Amirreza,Maruzewski, Pierre,Avellan, Francois Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.1
The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.
Chen, Changkun,Nicolet, Christophe,Yonezawa, Koichi,Farhat, Mohamed,Avellan, Francois,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.3
The effects of acoustic modes in the penstock on the self-excited oscillation in hydraulic power system were studied by assuming a finite sound velocity in the penstock. The flow in the draft tube is considered to be incompressible assuming that the length of the draft tube is smaller than the wavelength of the oscillation. It was found that various acoustic modes in the penstock can become unstable (amplified) by the diffuser effect of the draft tube or the effect of swirl flow from the runner. Their effects on each mode are discussed.
Alligne, S.,Nicolet, C.,Allenbach, P.,Kawkabani, B.,Simond, J.J.,Avellan, F. Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.4
Hydroelectric power plants are known for their ability to cover variations of the consumption in electrical power networks. In order to follow this changing demand, hydraulic machines are subject to off-design operation. In that case, the swirling flow leaving the runner of a Francis turbine may act under given conditions as an excitation source for the whole hydraulic system. In high load operating conditions, vortex rope behaves as an internal energy source which leads to the self excitation of the system. The aim of this paper is to identify the influence of the full load excitation source location with respect to the eigenmodes shapes on the system stability. For this, a new eigenanalysis tool, based on eigenvalues and eigenvectors computation of the nonlinear set of differential equations in SIMSEN, has been developed. First the modal analysis method and linearization of the set of the nonlinear differential equations are fully described. Then, nonlinear hydro-acoustic models of hydraulic components based on electrical equivalent schemes are presented and linearized. Finally, a hydro-acoustic SIMSEN model of a simple hydraulic power plant, is used to apply the modal analysis and to show the influence of the turbine location on system stability. Through this case study, it brings out that modeling of the pipe viscoelastic damping is decisive to find out stability limits and unstable eigenfrequencies.
Strain conservation in implantation -doped GeSi layers on Si(100)
Im, S.,Nicolet, M.A. The Korean Vacuum Society 1997 Applied Science and Convergence Technology Vol.6 No.1
Metastable pseudomorphic GeSi layers grown by vapor phase epitaxy on Si(100) substrates were implanted at room temperature. The implantations were performed with 90 KeV As ions to a dose of $1\times 10^{13}\;\textrm{cm}^2$ for $Ge_{0.08}Si_{0.92}$ layers and 709 keV $BF_2^+$ ions to a dose of $3\times 10^{13}\;\textrm{cm}^2$ for $Ge_{0.06}Si_{0.94}$layers. The samples were subsequently annealed for short 10-40 s durations in a lamp furnace with a nitrogen ambient or for a long 30 min period in a vacuum tube furnace. For $Ge_{0.08}Si_{0.92}$samples annealed for a 30 min-longt duration at $700^{\circ}C$ the dopant activation can only reach 50% without introducing significant strain relaxaion whereas samples annealed for short 40s periods (at $850^{\circ}C$) can achieve more than 90% activation without a loss of strain, For $Ge_{0.06}Si_{0.94}$samples annealed for either 40s or 30min at $800^{\circ}C$ full electrical activation of the boron is exhibited in the GeSi epilayer without losing their strain. However when annealed at $900^{\circ}C$ the strain in both implanted and unimplanted layers is partly relaxed after 30min whereas it is not visibly relaxed after 40s.
Experimental Study and Numerical Simulation of Cavity Oscillation in a Diffuser with Swirling Flow
Chen, Chang-Kun,Nicolet, Christophe,Yonezawa, Koichi,Farhat, Mohamed,Avellan, Francois,Miyazawa, Kazuyoshi,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.1
The cavity oscillation with swirling flow in hydraulic power generating systems was studied by a simple experiment and numerical simulation. Several types of fluctuation were observed in the experiment, including the cavitation surge caused by the diffuser effect and the vortex precession by the swirling flow. Both cavitation surge and vortex precession were simulated by CFD. Detailed flow structure was examined through flow visualization and CFD.
Experimental Study and Numerical Simulation of Cavity Oscillation in a Conical Diffuser
Chen, Chang-Kun,Nicolet, Christophe,Yonezawa, Koichi,Farhat, Mohamed,Avellan, Francois,Miyazawa, Kazuyoshi,Tsujimoto, Yoshinobu Korean Society for Fluid machinery 2010 International journal of fluid machinery and syste Vol.3 No.1
Based on the one-dimensional stability analysis, the self-excited oscillation in hydraulic power generating systems was studied by a simple experiment and numerical simulation. It was shown that a cavity in a conical diffuser can cause surge. With the diffuser, a high amplitude and low frequency oscillation occurs at low cavitation number. This oscillation was not observed with the straight pipe. It was confirmed that the diffuser effect of the draft tube can be the cause of the full load surge in hydraulic power system. Numerical results were also analyzed to check the validity of the one-dimensional stability analysis.