The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged ...The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term to account for the effects of vegetation.The three cases considered for open channels were two-stage rectangular channel with emerged vegetated floodplain,rectangular channel with submerged vegetated corner,and two-stage rectangular channel with submerged vegetated floodplain,respectively.To predict the depth-averaged velocity with submerged vegetated floodplains,we proposed a new method based on a two-layer approach where flow above and through the vegetation layer was described separately.Moreover,further experiments in the two-stage rectangular channel with submerged vegetated floodplain were carried out to verify the results.The analytical solutions of the cases indicated that the corresponding analytical depth-averaged velocity distributions agree well with the simulated and experimental prediction.The analytical solutions of the cases with theoretical foundation and without programming calculation were reasonable and applicable,which were more convenient than numerical simulations.The analytical solutions provided a way for future researches to solve the problems of submerged vegetation and discontinuous phenomenon of depth-averaged velocity at the stage point for compound channels.Understanding the hydraulics of flow in compound channels with vegetated floodplains is very important for supporting the management of fluvial processes.展开更多
This paper discusses the most recent case of the lost-wax process,namely,a bronze appendage with hollow snake patterns excavated in 2002 at the tomb of Duke Ning of Xu(許公寧)(a state in the Spring and Autumn period)i...This paper discusses the most recent case of the lost-wax process,namely,a bronze appendage with hollow snake patterns excavated in 2002 at the tomb of Duke Ning of Xu(許公寧)(a state in the Spring and Autumn period)in Ye County,Henan Province.Various physical and chemical analyses indicate that this artifact was cast as a whole in 547 BCE or slightly later in a high tin bronze alloy using the lost-wax process.No traces of cast joints or soldering were found.This research provides further proof that the lost-wax process was a significant technical development achieved by casters in the Pre-Qin period.展开更多
The absolute current distribution is usually the most desirable parameter in experiments involving a charged particle beam. The Faraday cup array technique, a direct measurement of the absolute current distribution, h...The absolute current distribution is usually the most desirable parameter in experiments involving a charged particle beam. The Faraday cup array technique, a direct measurement of the absolute current distribution, has been developed both in one dimension[1] and two dimensions[2], providing a great advantage in terms of convenience. In this technique, a many-channel picoammeter (up to 128 channels) is necessary.展开更多
The experiments with an internal target at a storage ring have many advantages. However, it is difficult to determine the absolute cross section of a reaction where luminosity cannot be simply established through macr...The experiments with an internal target at a storage ring have many advantages. However, it is difficult to determine the absolute cross section of a reaction where luminosity cannot be simply established through macroscopic measurements. Here we present an experimental determination of the effective target thickness from the beam energy losses at the internal target in HIRFL-CSRe. The measurements here are expected to provide the accurate target thickness and luminosity for the absolute cross-section study on future internal target experiments, and also provide some reference values for the study of beam loss mechanism of the heavy ion at HIRFL-CSRe.展开更多
Since the unexpected guiding effect of low energy ions by PET nanocapillaries was reported in the last decade[1], the self-organized charge-up on insulating surface is employed to realize a self-adaptive manipulation ...Since the unexpected guiding effect of low energy ions by PET nanocapillaries was reported in the last decade[1], the self-organized charge-up on insulating surface is employed to realize a self-adaptive manipulation of charged particle beams[2–4]. Considerable work (see Ref. [5] and references therein) has been done to investigate slow highly charged ions (SHCIs) interacting with inner surface of various insulating capillaries[5].展开更多
Double K-shell ionization of atoms by collisions with charged ions is one of typical two-electron processes andattracts considerable attention both in term of basic theory and experiment. Radiative de-excitation of th...Double K-shell ionization of atoms by collisions with charged ions is one of typical two-electron processes andattracts considerable attention both in term of basic theory and experiment. Radiative de-excitation of the doubleK-shell vacancy states of atoms leads to the emission of so called K X-ray hyper-satellites (Kh,Kh . . . )[1], whichgives us the insight into the decay modes of multiply ionized ions as well as the ionization processes during ion-atomcollisions. Contrary to the long-winded and difficult experiments with heavy target due to the low detection efficiencyof K X-ray hyper-satellites with crystal spectrometers[2??4], the bulk of knowledge concerning double K-shellionization in ion-atom collisions has been obtained for light target.展开更多
The guiding effect of 3 keV Ne7+ ions passing through an insulating PET nanocapillaries was found in 2002by N. Stolterfoht et al[1]. Since then considerable work[2] has been done to investigate slow highly charged ion...The guiding effect of 3 keV Ne7+ ions passing through an insulating PET nanocapillaries was found in 2002by N. Stolterfoht et al[1]. Since then considerable work[2] has been done to investigate slow highly charged ions(HCIs) interacting with inner surfaces of various insulating capillaries. It has been shown that the guiding effect isprevalent in the transmission of slow HCIs.Similar guiding phenomena were also observed for electrons transmitted through capillaries (see, e.g., Ref. [3-5]).However, the experiments showed that transmission efficiency of electrons was significantly lower than that of HCIs.Moreover, it revealed that portion of the transmitted electrons suffered significant energy-loss.展开更多
When an energetic highly charged ion (HCI) collides with an atom, the target electrons may be captured by theprojectile ion, either radiatively or non-radiatively. During a radiative electron capture (REC), a target e...When an energetic highly charged ion (HCI) collides with an atom, the target electrons may be captured by theprojectile ion, either radiatively or non-radiatively. During a radiative electron capture (REC), a target electronis transferred to the projectile accompanying with a photon emission, which carries away the excess energy andmomentum. During a non-radiative electron capture (NRC), the energy and momentum conservations are ensuredby the target nucleus[1]. If the captured electrons are populated in excited states, photons maybe emitted duringthe following stabilization processes, and therefore the X-ray spectrum can provide information about the initialpopulation. However, if a solid target is employed, the single-collision condition cannot be ensured when consideringthe capture processes, as well as strong background will be produced[2]. With the development of heavy ioncooling storage rings, the experimental luminance is enhanced by the strong ion beams when a gaseous target isprerequisite[3].展开更多
基金Under the auspices of National Basic Research Program of China(No.2011CB403303)National Key Research and Development Program of China(No.2016YFC0402408-5)National Natural Science Foundation of China(No.51179181,40788001)
文摘The lateral distributions of depth-averaged velocity in open compound channels with emerged and submerged vegetated floodplains were analyzed based on the analytical solution of the depth-integrated Reynolds-Averaged Navier-Stokes equation with a term to account for the effects of vegetation.The three cases considered for open channels were two-stage rectangular channel with emerged vegetated floodplain,rectangular channel with submerged vegetated corner,and two-stage rectangular channel with submerged vegetated floodplain,respectively.To predict the depth-averaged velocity with submerged vegetated floodplains,we proposed a new method based on a two-layer approach where flow above and through the vegetation layer was described separately.Moreover,further experiments in the two-stage rectangular channel with submerged vegetated floodplain were carried out to verify the results.The analytical solutions of the cases indicated that the corresponding analytical depth-averaged velocity distributions agree well with the simulated and experimental prediction.The analytical solutions of the cases with theoretical foundation and without programming calculation were reasonable and applicable,which were more convenient than numerical simulations.The analytical solutions provided a way for future researches to solve the problems of submerged vegetation and discontinuous phenomenon of depth-averaged velocity at the stage point for compound channels.Understanding the hydraulics of flow in compound channels with vegetated floodplains is very important for supporting the management of fluvial processes.
文摘This paper discusses the most recent case of the lost-wax process,namely,a bronze appendage with hollow snake patterns excavated in 2002 at the tomb of Duke Ning of Xu(許公寧)(a state in the Spring and Autumn period)in Ye County,Henan Province.Various physical and chemical analyses indicate that this artifact was cast as a whole in 547 BCE or slightly later in a high tin bronze alloy using the lost-wax process.No traces of cast joints or soldering were found.This research provides further proof that the lost-wax process was a significant technical development achieved by casters in the Pre-Qin period.
文摘The absolute current distribution is usually the most desirable parameter in experiments involving a charged particle beam. The Faraday cup array technique, a direct measurement of the absolute current distribution, has been developed both in one dimension[1] and two dimensions[2], providing a great advantage in terms of convenience. In this technique, a many-channel picoammeter (up to 128 channels) is necessary.
基金National Natural Science Foundation of China (11105201, U1532130, U1332206)
文摘The experiments with an internal target at a storage ring have many advantages. However, it is difficult to determine the absolute cross section of a reaction where luminosity cannot be simply established through macroscopic measurements. Here we present an experimental determination of the effective target thickness from the beam energy losses at the internal target in HIRFL-CSRe. The measurements here are expected to provide the accurate target thickness and luminosity for the absolute cross-section study on future internal target experiments, and also provide some reference values for the study of beam loss mechanism of the heavy ion at HIRFL-CSRe.
文摘Since the unexpected guiding effect of low energy ions by PET nanocapillaries was reported in the last decade[1], the self-organized charge-up on insulating surface is employed to realize a self-adaptive manipulation of charged particle beams[2–4]. Considerable work (see Ref. [5] and references therein) has been done to investigate slow highly charged ions (SHCIs) interacting with inner surface of various insulating capillaries[5].
文摘Double K-shell ionization of atoms by collisions with charged ions is one of typical two-electron processes andattracts considerable attention both in term of basic theory and experiment. Radiative de-excitation of the doubleK-shell vacancy states of atoms leads to the emission of so called K X-ray hyper-satellites (Kh,Kh . . . )[1], whichgives us the insight into the decay modes of multiply ionized ions as well as the ionization processes during ion-atomcollisions. Contrary to the long-winded and difficult experiments with heavy target due to the low detection efficiencyof K X-ray hyper-satellites with crystal spectrometers[2??4], the bulk of knowledge concerning double K-shellionization in ion-atom collisions has been obtained for light target.
文摘The guiding effect of 3 keV Ne7+ ions passing through an insulating PET nanocapillaries was found in 2002by N. Stolterfoht et al[1]. Since then considerable work[2] has been done to investigate slow highly charged ions(HCIs) interacting with inner surfaces of various insulating capillaries. It has been shown that the guiding effect isprevalent in the transmission of slow HCIs.Similar guiding phenomena were also observed for electrons transmitted through capillaries (see, e.g., Ref. [3-5]).However, the experiments showed that transmission efficiency of electrons was significantly lower than that of HCIs.Moreover, it revealed that portion of the transmitted electrons suffered significant energy-loss.
文摘When an energetic highly charged ion (HCI) collides with an atom, the target electrons may be captured by theprojectile ion, either radiatively or non-radiatively. During a radiative electron capture (REC), a target electronis transferred to the projectile accompanying with a photon emission, which carries away the excess energy andmomentum. During a non-radiative electron capture (NRC), the energy and momentum conservations are ensuredby the target nucleus[1]. If the captured electrons are populated in excited states, photons maybe emitted duringthe following stabilization processes, and therefore the X-ray spectrum can provide information about the initialpopulation. However, if a solid target is employed, the single-collision condition cannot be ensured when consideringthe capture processes, as well as strong background will be produced[2]. With the development of heavy ioncooling storage rings, the experimental luminance is enhanced by the strong ion beams when a gaseous target isprerequisite[3].
