Nuclear Structure Investigations of some Medium-Weight Isotopes

<p>This thesis describes the methods and results of investigations made to determine the decay schemes of three short-lived isotopes 112Ag, 114Ag and 116Ag. A total of 76 gamma-rays was observed with a Ge(Li) detector in the gamma-radiation which follows the Beta-decay of 112Ag to levels of 112Cd. gamma- gamma coincidence and angular correlation measurements were made with Ge(Li)-NaI(T1) and NaI(T1)-NaI(T1) systems. A decay scheme consistent with the present data is proposed. Cross sections for the reactions 112Cd(n,p)112Ag and 115In(n, alpha)112Ag were measured, and the half-life of the 112Ag decay was found to be 3.14 plus-minus 0.01 hr. The decay scheme of 114Ag was studied with Ge(Li) gamma-ray detectors and plastic Beta-ray detectors. 9 of the 11 gamma-rays observed in the decay were incorporated into 114Cd level structure previously determined by conversion electron measurements on the 113Cd(n,gamma)114Cd reaction. The endpoint energy of the Beta-decay was determined as 4.90 plus-minus 0.26 MeV; no branching was evident in the Beta-spectrum. A decay scheme is proposed for which the Beta-branching was deduced from the measured gamma-ray yield and a calculated cross section value for the 114Cd(n,p)114Ag reaction. The 114Ag half-life was determined as 4.52 plus-minus 0.03 sec; a search for a previously reported isomeric state of 114Ag was unsuccessful. Ge(Li) and NaI(T1) gamma-ray detectors were used to study the direct and coincidence spectra that result from the decay of 116Ag, the half-life of which was found to be 2.50 plus-minus 0.02 min. 53 gamma-rays were observed from this decay. The Beta-branching to the 17 excited states of 116Cd in the proposed decay scheme was derived from the measured gamma-ray yield and a calculated cross section value for the 116Cd(n,p)Ag reaction. Spin and parity assignments for ihe energy levels of 116Cd are made. An investigation of the applicability of two collective models to nuclear structure typical of the Cd nuclei studied demonstrated that one of the models was misleading when applied to vibrational nuclei. A potential function was developed in the other model to extend the investigation to include a study of the transition between extremes of collective motion. This was used to examine the correspondence between nuclear level schemes representative of rotational and vibrational excitations.</p>

Nuclear Structure Investigations of some Medium-Weight Isotopes

<p>This thesis describes the methods and results of investigations made to determine the decay schemes of three short-lived isotopes 112Ag, 114Ag and 116Ag. A total of 76 gamma-rays was observed with a Ge(Li) detector in the gamma-radiation which follows the Beta-decay of 112Ag to levels of 112Cd. gamma- gamma coincidence and angular correlation measurements were made with Ge(Li)-NaI(T1) and NaI(T1)-NaI(T1) systems. A decay scheme consistent with the present data is proposed. Cross sections for the reactions 112Cd(n,p)112Ag and 115In(n, alpha)112Ag were measured, and the half-life of the 112Ag decay was found to be 3.14 plus-minus 0.01 hr. The decay scheme of 114Ag was studied with Ge(Li) gamma-ray detectors and plastic Beta-ray detectors. 9 of the 11 gamma-rays observed in the decay were incorporated into 114Cd level structure previously determined by conversion electron measurements on the 113Cd(n,gamma)114Cd reaction. The endpoint energy of the Beta-decay was determined as 4.90 plus-minus 0.26 MeV; no branching was evident in the Beta-spectrum. A decay scheme is proposed for which the Beta-branching was deduced from the measured gamma-ray yield and a calculated cross section value for the 114Cd(n,p)114Ag reaction. The 114Ag half-life was determined as 4.52 plus-minus 0.03 sec; a search for a previously reported isomeric state of 114Ag was unsuccessful. Ge(Li) and NaI(T1) gamma-ray detectors were used to study the direct and coincidence spectra that result from the decay of 116Ag, the half-life of which was found to be 2.50 plus-minus 0.02 min. 53 gamma-rays were observed from this decay. The Beta-branching to the 17 excited states of 116Cd in the proposed decay scheme was derived from the measured gamma-ray yield and a calculated cross section value for the 116Cd(n,p)Ag reaction. Spin and parity assignments for ihe energy levels of 116Cd are made. An investigation of the applicability of two collective models to nuclear structure typical of the Cd nuclei studied demonstrated that one of the models was misleading when applied to vibrational nuclei. A potential function was developed in the other model to extend the investigation to include a study of the transition between extremes of collective motion. This was used to examine the correspondence between nuclear level schemes representative of rotational and vibrational excitations.</p>

DEFORMATION ANALYSIS OF LAYERED REINFORCED CONCRETE - FOAM CONCRETE FLOOR SLABS

This article presents a theoretical study of a stress-strain state of layered reinforced concrete - foam concrete floor slabs (hereinafter called as the LRFCS), with the use of a deformation analysis. Compressive and tensile diagrams of the foam concrete, a tensile diagram of the reinforced concrete and compressive and tensile diagrams of the reinforcement rod are used for the estimation of the stress-strain state of the calculated cross-section of the LRFCS. It should be noted that this article presents the deformation method of loading by the scheme of pure bending for the LRFCS. This deformation method of loading is determined by six shapes of the stress-strain state. These shapes of the stress-strain state are represented by the corresponding distribution diagrams of the relative deformations and the distribution diagrams of internal stresses in the calculated cross-section of the floor slab. Also, this article presents the corresponding equilibrium equations of internal efforts and moments, which act in the calculated cross-section of the floor slab for all shapes of its stress-strain state. Consequently, the mentioned recommendations and mathematical dependencies allow to evaluate the stress-strain state of the LRFCS from its initial loading to its destruction.

EVALUATION OF DESIGN FIRE RESISTANCE OF A REINFORCED CONCRETE BEAM WITH CENTRAL PROP

The article describes the essence of the technological method of testing a reinforced concrete beam with central prop for fire resistance without destruction, based on a set of individual indicators of the quality of concrete and reinforcement. The influence of the geometrical dimensions of a reinforced concrete beam with central prop, the heating pattern of the calculated cross section under fire conditions, the placement of the reinforcement in the calculated cross section, the depth and degree of fire protection of the concrete, the coefficient of thermal diffusion of concrete, the magnitude of the test load on the beam and the stress intensity in the bars of the longitudinal working reinforcement were investigated. The fire resistance limit of a beam with central prop is determined by the sign of loss of bearing capacity using the analytical equation (1). The use of the new proposed technological method allows to determine the actual fire resistance of a two-span reinforced concrete beam without full-scale fire impact, simplifies engineering calculations, increases the reliability of static material quality control and non-destructive testing, reduces economic costs.

Seismic Performance of Full-Scale Joints Composed by Concrete-Filled Steel Tube Column and Reinforced Concrete Beam with Steel Plate-Stud Connections

A concrete-filled steel tube (CFST) column has the advantages of high bearing capacity, high stiffness, and good ductility, while reinforced concrete (RC) structure systems are familiar to engineers. The combinational usage of CFST and RC components is playing an important role in contemporary projects. However, existing CFST column-RC beam joints are either too complex or have insufficient stiffness at the interface, so their practical engineering application has been limited. In this study, the results of a practical engineering project were used to develop two kinds of CFST column-RC beam joints that are connected by vertical or U-shaped steel plates and studs. The seismic performance of full-scale column-beam joints with a shear span ratio of 4 was examined when they were subjected to a low-cyclic reversed loading test. The results showed a plump load-displacement curve for the CFST column-RC beam joint connected by steel plates and studs, and the connection performance satisfied the building code. The beam showed a bending failure mode similar to that of traditional RC joints. The failure area was mainly concentrated outside the steel plate, and the plastic hinge moved outward from the ends of the beam. When the calculated cross section was set at the ends of the beam, the bending capacity of joints with the vertical or U-shaped steel plates and studs increased compared to the RC joint. However, when the calculated cross section was set to the failure area, the capacity was similar to that of the RC joint. The proposed joints showed increases in the energy dissipation, average energy dissipation coefficient, and ductility coefficient compared to the RC joint.

NEUTRALINO–NUCLEON INTERACTION IN THE SPLIT SUSY SCENARIO OF THE DARK MATTER

The split SUSY scenario with light Higgsino states is treated as an application to the dark matter problem. We have considered the structure of the neutralino–nucleon interaction and calculated cross-section of the neutralino–nucleon scattering. The decay properties of the lightest chargino and next lightest neutralino are analyzed in details.

DYNAMICS OF O + O3 REACTION ON A NEW POTENTIAL ENERGY SURFACE FOR GROUND-TRIPLET TETRAOXYGEN: SPECTATOR BOND MECHANISM REVISITED

We report a dynamics study of the reaction [Formula: see text] using an improved double many-body expansion (DMBE II) potential energy surface for the ground triplet state of O 4. Values of the calculated cross section, vibrational and rotational distributions, as well as thermal rate coefficient as a function of temperature are given. While some discrepancy with experiment is found in the rotational distribution of the product O 2 molecules with vibrational quantum number v = 12, the agreement is quite good for the thermal rate coefficient over the whole range of temperatures where theory and experiment overlap. No breakdown of a previously suggested spectator bond mechanism is observed. Reasons to support such an evidence are given from ab initio calculations by looking at the variation of the energy and calculated bond distances as a function of the intrinsic reaction coordinate along the products channel.