[en] Limit pressures and corresponding maximum local membrane Stress Concentration Factors (SCF) are assessed for two orthogonally intersecting thin-walled cylindrical shells subjected to internal pressure. The limit pressures of 81 models with parameters ρ=d/D≤0.8, D/T≥10, d/t≥10, λ=d/√DT≤8 and d/D≤t/T≤2 are calculated using inelastic analyses by the 3D finite element method (3D FEM) in which the material is elastic-perfectly plastic. The plastic collapse pressures obtained by 3D FEM are in good agreement with test results presented by previous authors. The local membrane SCF at the intersections of two cylindrical shells subjected to the limit pressure load is calculated by elastic thin shell theoretical solutions presented by Xue and Hwang. The local membrane SCF decreases significantly as t/T increases, and decreases little as d/√DT decreases when D/T is fixed. The local membrane SCF increases significantly as D/T increases, and varies little as d/√DT increases when t/T is constant. The local membrane stress criterion k^m≤2.2 for reinforcement design of openings in a cylindrical pressure vessel subjected to internal pressure can be accepted generally except for a few cases of large thickness ratio t/T, and small opening ratio ρ

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No abstract available

No abstract available

[en] The blueschists from Qingshuigou in the Northern Qilian Mountains suffered multiple metamorphism with a typical clockwise P-T-t path that is interpreted to represent a subduction evolution process. The white mica 40Ar/39Ar cooling ages are 442.l-447.5 Ma and 445.7-453.9 Ma. The protolith of the blueschist first subducted to the depth and suffered initial metamorphism with close peak pressure (8-10 kbar, 326-339 ^oC), Sequentially, it underwent an isobaric heating process to reach the peak temperature (470-490 ^oC), then (445.7-453.9 Ma) the subducted ocean crust began to exhume and to cool with decreasing pressure and suffered retrograde metamorphism between 460-440 and 400-380 Ma. A detailed survey of 40Ar/39Ar mineral dating was carried out an basement rocks of the Eastern Kunlun Mountains. The samples were collected from Jinshuikou, Kuhai, Xiaomiao, Wanbaogou and Nachitai groups. The results of 40Ar/39Ar dating include four age groups that are 363-438 Ma, 205-242 Ma, 117-172 Ma and ca. 32 Ma. The age group of 363-438 Ma is interpreted to represent the cooling after the Caledonian amphibolite-grade metamorphism coupled with the closure of a small ocean basin. The age group of 205-242 Ma represents the cooling after the Indonesian metamorphism overprint, which implicates that a major ocean (between Gondwana and Eurasia) closed due to N-ward Qiangtang block accretion. The age group of 117-172 Ma should be related to ductile deformation along the Xidatan fault due to the northward directed accretion of the Lhasa block. The lower-grade overprint age of ca. 32 Ma represents a late-stage exhumation event. The Radstadt Mountains, Eastern Alps expose the tectonic boundary between the base of the Austroalpine continental plate (hangingwall) and the Penninic oceanic units (foot wall). From hanging wall to foot wall the following age sequence can be observed. The Gurpitscheck and Tweng units, part of the Austroalpine basement, were penetratively deformed due to ongoing rifting of the continental crust during the Permian (290 - 250 Ma). Austroalpine Permo-Mesozoic cover rocks were deformed during the Cretaceous (around 80 Ma) and the Paleogene (55 - 50 Ma), the latter ages found in deeper tectonic levels and represent the collision of Austroalpine and Penninic tectonic units. The Penninic nappe complex displays a rather continuous decrease of ages from c. 37 to 25 Ma from high to deep levels. A second age group of c. 22 Ma was found both in low-temperature release steps and as plateau ages in higher parts of the Penninic unit. It is attributed to a thermal overprint due to ductile extension of the over thickened orogenic wedge. These new age data show that tectonic accretion lasted over a period of more than 65 - 50 Ma. (author)

[en] In this dissertation both theoretical and experimental aspects of FIR LMR spectroscopy are discussed with particular emphasis on the radicals CF and CH₂Br. Chapter 1 reviews the development and salient features of LMR. After a discussion of the basic concepts and principles of LMR in Chapter 2, Chapter 3 gives a detailed description of the Cambridge FIR LMR spectrometer used to search for new FIR laser lines and to record the spectra of CH₂Br and CF. The last section in this chapter is devoted to the methods of generating free radicals. It describes the microwave discharge method with a modified 'Evenson cavity' and the development of a novel selective radical source, the alkali metal atom reaction source. The capability and potential of the latter method has been demonstrated by production of the well known CH radical. In Chapter 4 the operating principles of FIR lasers are discussed in detail and 32 new FIR laser lines are reported, with an actual assignment of two of the new CH₂CF₂ lines. Chapter 5 presents a comprehensive study of the FIR spectroscopy of the CF radical. It includes the detection of the LMR spectra of vibrationally excited CF in its ground electronic state, a description of the effective Hamiltonian and computer programs, and a full analysis of the Zeeman data in terms of a spin decoupled Hund's case (a) basis set. All the previous spectral data involving v≥1 vibrational states are included in a global least-squares fit to determine the vibrational dependence of all the major molecular parameters. Several v=1 parameters have been determined for the first time. The results constitute the definitive parameters for the v=1 state of CF. Finally, the FIR LMR spectra of CH₂Br, the first high resolution spectra of this radical in the gas phase, are described in Chapter 6. Due to the complexity of the spectra and the lack of spectroscopic information from other high resolution techniques, the CH₂Br spectra have not yet been completely assigned and analysed. However, this study did allow the determination of the (B+C) value of the radical. (author)

[en] A graphical method to obtain the general multi-pion correlation functions for a partially coherent pion source is proposed. In an application of this technique, the general four-pion correlation function is obtained for the first time. A modified Gaussian mode for a partially coherent source is proposed. The three-pion and four-pion correlation function, and the relation between two pion, three-pion and four-pion coherence factors for the partially coherent Gaussian source are given. The general forms of the coherence factors and the correlation functions of higher order multi-pion interference are revealed

[en] Refractory inclusions from Kaba (CV3) chondrite were studied by instrumental neutron activation analysis (INAA) and electron probe microanalysis (EPMA). The inclusions observed cover a wide range of chemical patterns, mineral assemblages and textures, indicating the complexity of early solar nebular conditions. The elemental abundances normalized by C1 chondritic abundances vary smoothly as a function of their volatilities, suggesting these inclusions were formed by condensation/evaporization processes in the primeval solar nebula. The average REE pattern of Group Ill inclusions has an enrichment of 31 x Cq with approximately equal depletions of Eu and Yb (Eu/Eu^* = 0.33, Yb/Yb^* = 0.29). Group 11 inclusions are irregularlyshaped aggregates of rounded or sub-rounded melilite-rich nodules rimmed with mono-mineralic layers of high-Al phase, Ti-Al pyroxene and hedenbergite. The lower enrichment of Al, Ti and Ca is interpreted by the partial vaporization of the inclusion by a transient event in an oxidizing environment near the nebular midplane. This process caused the partial lose of Al, Ti, Ca and more volatile elements. The rim is the resultant vaporization residue. This model combines the modification of refractory elemental pattem and the rim formation in one event. The partial evaporization of a precursor inclusion with an unfractionated REE pattern would form a rim where Yb and Eu are strongly depleted in different degrees, and the interior is not effected. The similarities between Kaba and Allende in whole-rock composition and their inclusion mineralogies and textures suggest they were formed in a generally similar nebular region

[en] We have demonstrated that in general, Hara's theorem, which gives various symmetry relations for the weak radiative decays of baryons, is not valid. A new set of symmetry relations was established in this thesis. The weak radiative decays are long distance interaction in nature which could be described either by the pole model approximations or the four quark transition in the quark model calculation. Within the accuracy of the calculation, we demonstrate that these two approaches are consistent and give similar results. The old pole model calculation neglects the leading order parity violating contribution. We also demonstrate that both quark model and pole model calculations satisfy the symmetry relations we derived. The theoretical predictions for the decay rates agree well with experiments. The predictions for the asymmetry parameters will be checked in the future experiment. Our predictions on the asymmetries are very different from all previous results. The large negative asymmetry parameter for the Σ⁺ → P_γ decay is explained by the fact that there is a large symmetry breaking effect in the parity conserving sector instead of the parity violating sector, as previously thought

[en] Experiments with beams of short-lived radioactive nuclei will advance our understanding of the structure of nuclei far from stability and the key reactions in stellar processes which power the universe. At the former Holifield Radioactive Ion Beam Facility (HRIBF), radioactive ion beams (RIBs) were produced using the Isotope Separator On-Line (ISOL) technique. The ISOL method can produce high-intensity RIBs with very good phase-space properties. However, the purity of the RIBs is often limited. In many cases, the isotopes of interest are produced at much lower yields than many neighboring isobars and the resolution of the mass separators are insufficient to deliver the desired isotopes with sufficient intensity and low isobaric contamination. To address this problem, various beam purification techniques were used or investigated at HRIBF to improve the elemental selectivity of the ion sources or to add an isobar suppression step in the ISOL process, including molecular side-band, selective adsorption, resonant laser ionization, ion beam cooling, and selective photodetachment; each has its unique advantages and applications. (author)