共查询到20条相似文献,搜索用时 218 毫秒
1.
A system employing the radio frequency holographic method for the measurement of the reverberation time of an acoustic chamber is proposed. This system has the advantage of supplying visible information on the diminishing intensity of the acoustic wave. A simple mathematical model has been taken to discuss the basic principles involved in the system. A possible experimental set-up for the measurement of the reverberation time is described in detail. 相似文献
2.
纳米TiO_2-活性炭的制备及光催化脱汞初探 总被引:4,自引:0,他引:4
采用溶胶凝胶法以活性炭(AC)为载体,制备纳米TiO_(2-)活性炭复合物(TiO_(2-)AC).采用X射线衍射仪(XRD),场发射扫描电镜结合X射线能谱分析仪(FSEM-EDX)对TiO_(2-)AC复合物进行表征。在波长为253.7 nm的紫外光照射下进行TiO_(2-)AC光催化氧化脱除单质汞试验。结果表明,复合物表面TiO_2纳米粒子尺寸可控制在30 nm左右;热处理温度的升高促进TiO_2晶粒的生长及相变,复合物中TiO_2锐钛矿相向金红石相转变的温度在500~700℃之间;负载锐钛矿型TiO_2的复合物较金红石型复合物显示出更强的光催化脱汞效果。TiO_(2-)AC能够达到预期的结合TiO_2光催化氧化性能与活性炭强吸附能力的效果,脱汞性能显著,具有广阔的应用前景。 相似文献
3.
Lheureux D Decremps F Fischer M Polian A Itie JP Syfosse G Zarembowitch A 《Ultrasonics》2000,38(1-8):247-251
Our objective consists in validating a new set-up which will permit us to carry out simultaneously ultrasonic and X-ray diffraction measurements under pressure. To validate the results obtained by this new set-up, the elastic properties of a single crystal of germanium were studied. Our results are in good agreement with those of Goncharova et al. and McSkimin and Andreatch. The results of the present study are compared with those of Menoni et al. and obtained by X-ray diffraction in a diamond anvil cell. 相似文献
4.
In recent years there has been a growing interest in the application of X-ray scattering techniques to biomolecules in solution. At NSLS, a new undulator-based beamline, X9, has been constructed to address the oversubscribed user demand for X-ray scattering. Beamline X9 has the capability to perform small/wide-angle X-ray scattering (SAXS/WAXS) all in one single instrument. This is accomplished by utilizing a vacuum sample/detector chamber that is an integral part of the SAXS scattering flight path. This vacuum chamber allows a WAXS detector to be positioned at a close distance from the sample, while not interfering with scattered X-rays at small angles from reaching the SAXS detector. A regular training program, the X9 workbench, has also been established to allow users to become familiar with beamline X9 for solution X-ray scattering. 相似文献
5.
Optical and surface spectroscopies as well as nanoindentation techniques have been used to study ZrN coatings on 316L stainless steel obtained by DC-reactive magnetron sputtering. The deposit process was carried out using initial and working pressures of 10−6 Torr and 10−3 Torr, respectively. The experimental set-up for optical spectra acquisition was designed for the study in situ of the plasma in the deposition chamber. Auger spectroscopy, SEM and X-ray diffraction were used to characterize the coatings. Nanoindentation tests were carried out to measure the mechanical properties of the coating. Plasma characterization revealed the presence of CN molecules and Cr ions in the plasma. Surface spectroscopy results showed that ZrN, Zr3N4 and ZrC coexist in the coating. These results allowed the understanding of the mechanical behavior of the coatings, demonstrating the importance of the plasma characterization as a tool for tailoring the properties of hard coatings. 相似文献
6.
P. Schmalbrock H. W. Becker L. Buchmann J. Görres C. Rolfs H. P. Trautvetter W. S. Rodney 《Zeitschrift für Physik A Hadrons and Nuclei》1983,310(3):243-245
A search forγ-ray transitions within the broad groundstate of5Li has been carried out via the4He(p, γp *)4He reaction atE p (lab)=1.5?7.0 MeV. Differentially pumped gas targets of the extended and quasi-point types have been used. The results show that the set-up and detection techniques utilized are not sensitive enough to observe such intrastate transitions. 相似文献
7.
8.
A. A. Kornilova V. I. Vysotskii N. N. Sysoev A. V. Desyatov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2009,3(2):275-283
The paper presents the results of studying the combined shock-wave radiation-emission processes associated with cavitation phenomena that occur at fast directional motion of a liquid jet into a closed working chamber through narrow dielectric channels. These processes induce high-power tunable X-ray radiation outside the chamber. At a relatively small liquid pressure, cavitation has been shown to generate shock waves in the chamber walls, which excites surface atoms and leads to the emission of X-rays from the outer surface of the chamber. At a high liquid pressure, the liquid jet does not touch the chamber walls and the cavitational shock waves lead to the excitation of the surface atoms of the jet itself accompanied by the generation of optical and X-ray radiation in the jet, which has been also observed in experiments. 相似文献
9.
Abstract A method for plate-impact dynamic compaction of copper powder has been developped. The optimization of the experimental set-up (impedance adjustments, tensile wave traps, relative thickness of impactor and target,…) is presented. 2D axisymetrical numerical simulations have been performed with a Lagrangian finite element code. Geometrical characteristics of the experimental set-up as well as the dynamic response of the powder (Reaugh equation of state) and of the material of the set-up have been taken into account. These simulations show that, due to the difference in shock velocities in the container and in the powder, the powder is submitted to 2D loading waves. As a matter of fact the powder may be loaded by a non-planar shock wave propagating in the as-expected direction, as well as by a sweeping wave initiated at the bottom of the powder container, and propagating obliquely from the bottom-up. This second wave loads the bottom of the powder first. The influence of the impactor thickness as well as its material on the shock front shape and on the shock density-pressure history of the material has been studied. 1D simulations are shown not to evaluate properly the stress history and the energy deposition in the powder sample. Metallographic observations as well as X-ray tomography experiments have been performed on consolidated samples. A very good agreement has been found between results of 2D numerical simulations and the observed final shape and density maps of the samples. The shape of deformed powder particles are also in agreement with the expected shock history. 相似文献
10.
At the Prague Asterix Laser System Center (PALS) the Asterix iodine laser delivering up to 700 J/0.5 ns is used as a pump
source for X-ray laser experiments and applications. The prepulse technique was applied which is known to improve the neon-like
X-ray laser output at the J = 0-1 transition dramatically. Since Zn slab targets were used the operating wavelength was 21.2 nm. A prepulse having up
to 20 J precedes the main pulse by 10 ns. The main beam and the prepulse beam are focussed by two different optical systems
separately and their foci are superimposed at the target surface. By implementing a half-cavity set-up for double-pass amplification
using a Mo/Si multilayer mirror - which can be used for more than 100 shots - the X-ray laser output was more than 10 times
stronger than at the single pass in a 30 mm long plasma. Double-pass amplification was observed to be most efficient when
the pump pulse duration was at least 150 ps longer than the round trip time ( ≈ 260 ps) in the half-cavity. Under this fundamental
condition the X-ray laser reached saturation in the double-pass regime containing approx. 4 mJ energy which has been proved
to be enough for future applications. In this contribution, the X-ray laser features like divergence in two dimensions, the
beam quality (symmetry), the pointing angle and the integrated intensity giving an estimation of the output energy are investigated
over 110 shots. To characterize the stability of the X-ray laser the shot distribution, the mean value and the standard deviation
for these parameters are evaluated. For 18 shots in a series - what was achievable during one day - the corresponding values
are given, and a statistical analysis carrying out a chi-squared test characterize the Zn X-ray laser as a robust tool suitable
for applications. In the future it is planned to allocate X-ray laser beam time to external research groups.
Received 17 May 2002 / Received in final form 10 September 2002 Published online 6 November 2002
RID="a"
ID="a"e-mail: praeg@fzu.cz 相似文献
11.
A free-air ionization chamber in low-energy X-ray has been designed and manufactured at theNational Institute of Metrology (NIM, China) according to the defination of alr-kerma. The results of a preliminary test show that the leakage current of ionization chamber is around 2×10<'-15>A, and the correction factor of ion recombination for the ionization chamber is also obtained. The free-air ionization chamber is suitable for the primary standard in low-energy X-rays. 相似文献
12.
利用强流电子束技术产生通量密度为1018—1019X-ray photon/sr·s的脉冲CuKX射线源,标定PIN型硅二极管半导体探测器对X光子的脉冲灵敏度。用绝对X射线监测器——P10气体脉冲电离室作为脉冲X射线通量密度的标准。脉冲电荷自动测量仪由微处理机进行程序控制,并予以实时校准。该电离室测量通量密度的精度为±5%,适用的能通量率范围可达4×10-9—2×102W/cm2,适用的光子能量范围为1.5—10keV,标定探测器的精度为±7.0%,并发现PIN型硅二极管的脉冲灵敏度比稳态X射线束标定的灵敏度高30%左右。
关键词: 相似文献
13.
Elastic properties of single crystalline germanium have been determined up to 6 GPa. All three elastic constants and their pressure derivative have been obtained by transit time measurements in a large volume cell. Comparison with previously published data fully validate the proposed set-up. The design of this set-up allows simultaneous in situ ultrasonic and X-ray diffraction measurements. 相似文献
14.
Cu(2)O nanopowders have been prepared by ultrasound-assisted electrochemistry with a potentiostatic set-up. Their composition has been determined by X-ray diffraction and energy dispersive X-ray spectroscopy. Transmission electron microscopy and centrifugation analyses indicate that the nanopowders consist of agglomerates of variable nanometric diameter grain. Most of particles have a diameter of 8 nm whatever the electrodeposition potential. The influence of the parameters of electrochemical and ultrasonic pulses on the particle diameter was also studied. The specific surface areas determined by Brunauer-Emmet-Teller (BET) model are very high with a value close to 2000 m(2)g(-1). 相似文献
15.
ZHU YONG-SHENG ZHANG RUN-HUA ZHAO PING-DE XU ZHI-QING LI XIAO-GUANG ZHANG ZHI-JIE XU ZI-ZONG 《中国物理C(英文版)》1981,5(5):558-568
We have designed and operated a test module of multistep avalanche chamber with effective detection area of 9 by 9 cm2. Argon-acetone mixture gas is provided by a simple gas mixing system, and mixture ratio can be modulated by gas flow. The performance of the chamber has been investigated by use of 55Fe 5.9 keV X-ray source at acetone concentration in argon of 2.7%, and the effect of acetone concentration to the chamber has been measured. 相似文献
16.
S. Hazra 《Applied Surface Science》2006,253(4):2154-2157
Laboratory source X-ray scattering set-up has been used to determine the complete morphology and structure of an optically important composite thin film. Analysis of grazing incidence small angle X-ray scattering, X-ray reflectivity and powder diffraction data of Au/LiNbO3 thin film prepared by sequential deposition of gold and lithium niobate on float glass substrate suggest that the Au-nanocrystallites are dispersed in amorphous medium, which although have average separation but do not have any long range periodicity other than growth or z-direction. The morphology of the nanocomposite thin film determined through X-ray scattering measurements agrees well with the measured optical absorption. 相似文献
17.
18.
H.Koivisto P.Frondelius T.Koponen P.Lappalainen T.Ropponen M.Savonen P.Suominen O.Tarvainen K.Tinschert G.Ciavola 《中国物理 C》2007,31(Z1):41-45
Extensive plasma potential measurements have been carried out using a device developed at JYFL. In this article the main results of the measurements will be summarized.A new simulation code to study the electron heating is being developed.One objective of the code is to determine the change of the electron loss cone when the magnetic field component of the electromagnetic wave is taken into account along with the permittivity of the plasma.As a part of the work,accurate X-ray measurements have been initiated. A new plasma chamber based on the MMPS-concept(Modified MultiPole Structure)has successfully been constructed and tested with the JYFL 6.4GHz ECRIS.The results and conclusions will be presented elsewhere in these proceedings.In the same article,a new concept of ECRIS and first results will be presented.The active development work of evaporation ovens has been carried out in a joint European collaboration(ISIBHI). The objective of the task is to make the operation of the oven reliable at 2000℃for several days.Both resistively and inductively heated ovens have been studied and further developed.The status of this work will be presented. 相似文献
19.
This paper presents the performance of the human crystalline lens having gradient index (GRIN) structure in the presence of a moderate power laser pulse. Nonlinear dynamical equations have been set-up governing the laser pulse propagation in the lens by taking into account the nonlinearity introduced by the laser pulse. Semi-analytical results have been obtained by using the paraxial ray approximation when GRIN and nonlinearity effects are simultaneously present. Performance of the lens has been analyzed in two explicit cases. In the first case, only the GRIN structure is considered while in the second case the nonlinearity and the GRIN both are considered. A moderate power laser pulse can be used for self-focusing in the crystalline lens when GRIN effects alone are not sufficient to focus the laser pulse in the crystalline lens. 相似文献
20.