Thermally induced evolution of phase transformations in gas hydrate sediment

Thermally induced evolution of phase transformations is a basic physical-chemical process in the dissociation of gas hydrate in sediment (GHS). Heat transfer leads to the weakening of the bed soil and the simultaneous establishment of a time varying stress field accompanied by seepage of fluids and deformation of the soil. As a consequence, ground failure could occur causing engineering damage or/and environmental disaster. This paper presents a simplified analysis of the thermal process by assuming that thermal conduction can be decoupled from the flow and deformation process. It is further assumed that phase transformations take place instantaneously. Analytical and numerical results are given for several examples of simplified geometry. Experiments using Tetra-hydro-furan hydrate sediments were carried out in our laboratory to check the theory. By comparison, the theoretical, numerical and experimental results on the evolution of dissociation fronts and temperature in the sediment are found to be in good agreement.

我国成功进行重离子束治癌临床试验

<正>中国科学院近代物理研究所与兰州军区兰州总医院、甘肃省肿瘤医院等医疗单位密切合作,成功进行了重离子束浅层治癌临床试验,使我国成为世界上第四个完成重离子束治癌临床试验的国家.

Combined study of gamma p ->eta p and pi(-)p ->eta n in a chiral constituent quark approach

Within a chiral constituent quark model approach, η-meson production on the proton via electromagnetic and hadron probes is studied. With few parameters, the differential cross section and polarized beam asymmetry for γp → ηp and differential cross section for π − p → ηn processes are calculated and successfully compared with the data in the center-of-mass energy range from threshold up to 2 GeV. The five known resonances S11(1535), S11(1650), P13(1720),D13(1520), and F15(1680) are found to be dominant in the reaction mechanisms in both channels. Possible roles played by new resonances are also investigated; and in the photoproduction channel, significant contribution from S11 and D15 resonances, with masses around 1715 and 2090 MeV, respectively, are deduced. For the so-called missing resonances, no evidence is found within the investigated reactions. The helicity amplitudes and decay widths of N ∗ → πN, ηN are also presented and found to be consistent with the Particle Data Group values.

eta-production on the proton via electromagnetic and hadronic probes

The reactions pi(-)p -> eta n and gamma p -> eta p are investigated within a dynamical coupled-channels model of meson production reactions in the nucleon resonance region The meson-baryon channels included are pi N, pi Delta, sigma N, and rho N The direct eta-photoproduction process is studied within a formalism based on a chiral constituent quark model approach, complemented with a one-gluon-exchange mechanism, to take into account the breakdown of the SU(6)circle times O(3) symmetry In the models search, the following known nucleon resonances are embodied S-11(1535), S-11(1650), P-11(1440), P-11(1710), P-13(1720), D-13(1520), D-13(1700), D-15(1675), and F-15(1680). Data for the pi(-)p -> eta n reaction from threshold up to a total center-of-mass energy of W approximate to 2 GeV are satisfactorily reproduced For the photoproduction channel: two additional higher mass known resonances, P-13(1900) and F-15(2000), are also considered However, reproducing the data for gamma p -> eta p requires, within our approach, two new nucleon resonances, for which we extract, mass and width

Study of nucleon resonances in a chiral quark model via eta productions

In this report we investigate eta-meson productions oil the proton via electromagnetic and hadron probes in a chiral quark model approach. The observables, such as, differential cross section and beam asymmetry for the two productions are calculated and compared with the experiment. The five known resonances S-11(1535) S-11(1650); P-13(1720) D-13(1520), and F-15(1680) are found to be dominant in the reaction mech-anisms in both channels. Significant, contribution from a new S-11 resonances are deduced. For the so-called "missing resonances", no evidence is found within the investigated reactions. The partial wave amplitudes for pi(-)p -> eta n are also presented.

eta photoproduction on the proton in a chiral constituent quark approach via a one-gluon-exchange model

A formalism based on a chiral quark model (chi QM) approach complemented with a one-gluon-exchange model, to take into account the breakdown of the SU(6)circle times O(3) symmetry, is presented. The configuration mixing of wave functions for nucleon and resonances are derived. With few adjustable parameters, differential cross-section and polarized-beam asymmetry for the gamma p -> eta p process are calculated and successfully compared with the data in the center-of-mass energy range from threshold to 2 GeV. The known resonances S-11(1535), S-11(1650), P-13(1720), D-13(1520), and F-15(1680), as well as two new S-11 and D-15 resonances, are found to be dominant in the reaction mechanism. Moreover, connections among the scattering amplitudes of the chi QM approach and the helicity amplitudes, as well as decay widths of resonances, are established. Possible contributions from the so-called missing resonances are investigated and found to be negligible.

X-ray spectra induced by slow highly charged Arq+ ions in collision with Nb surface

The X-ray spectra of Nb surface induced by Arq+ (q = 16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar16+ ion was neutralized below the metal surface. The K shell electron of Ar16+ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar17+ is three magnitude orders larger than that of Ar16+.

垂直流人工湿地处理稠油废水的实验研究

采用垂直流人工湿地模拟装置对新疆油田外排含盐稠油废水进行了处理。实验表明:对于进水CODCr为402～406mg/L,盐度5701～5712mg/L,石油类40.62mg/L的含盐稠油废水,该系统的出水指标为CODCr35～38mg/L,盐度1535～1542mg/L,湿地系统对CODCr和盐分的去除率达到91%和73%;当水力停留时间为11d以上,出水石油类<5mg/L,处理后出水CODCr、石油类达到《污水综合排放标准》(GB8978-1996)的一级标准。

应用生态学的现状与展望

应用生态学是迅猛发展的现代生态学的主体 .寻求解决人口、资源、环境等问题是应用生态学发展的主要动力 .经过 4 0年的发展 ,应用生态学已发展成为一个庞大的学科门类 .应用生态学未来的发展应更多地关注受人类影响和管理的生态系统并将人视为生态系统的组成成分 .应用生态学在当前和今后应给予优先重视的研究领域 ,包括生态系统与生物圈的可持续利用、生态系统服务与生态设计、转基因生物的生态学评价、生物入侵生态学、流行病生态学、生态预报、生态过程及其调控等 .在今后若干年内 ,围绕这些领域 ,可能会出现广泛而活跃的研究热潮以及一些新的特点 .

Electrochemical properties of amorphous and icosahedral quasicrystalline Ti45Zr35Ni17Cu3 powders

Ti45Zr35Ni17Cu3 amorphous and single icosahedral quasicrystalline powders were synthesized by mechanical alloying and subsequent annealing at 855 K. Microstructure and electrochemical properties of two alloy electrodes were characterized. When the temperature was enhanced from 303 to 343 K, the maximum discharge capacities increased from 86 to 329 mAh g(-1) and 76 to 312 mAh g(-1) for the amorphous and quasicrystalline alloy electrodes, respectively. Discharge capacities of two electrodes decrease distinctly with increasing cycle number. The I-phase is stable during charge/discharge cycles, and the main factors for its discharge capacity loss are the increase of the charge-transfer resistance and the pulverization of alloy particles. Besides the factors mentioned above, the formation of TiH2 and ZrH2 hydrides is another primary reason for the discharge capacity loss of the amorphous alloy electrode.