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In photon activation analysis (PAA), relative methods are widely used because of their accuracy and precision. Absolute methods, which are conducted without any assistance from calibration materials, are seldom applied for the difficulty in obtaining photon flux in measurements. This research is an attempt to perform a new absolute approach in PAA - quasi-absolute method - by retrieving photon flux in the sample through Monte Carlo simulation. With simulated photon flux and database of experimental cross sections, it is possible to calculate the concentration of target elements in the sample directly. The QA/QC procedures to solidify the research are discussed in detail. Our results show that the accuracy of the method for certain elements is close to a useful level in practice. Furthermore, the future results from the quasi-absolute method can also serve as a validation technique for experimental data on cross sections. The quasi-absolute method looks promising. [ABSTRACT FROM AUTHOR]

In the present study we investigated the airflow patterns and air quality of a series of typical street canyon combinations, developed a mass balance model to determine the local pollutant dilution rate, and discuss the impact of upstream canyon on the air quality of downstream canyon. The results indicated that the geometrical size of upstream and downstream buildings have significant impacts on the ambient airflow patterns. The pollution distribution within the canyons varies with different building combinations and flow patterns. Within the upstream canyon, pollution always accumulates to the low building side for non-symmetrical canyon, and for symmetrical canyon high level of pollution occurs at the leeward side. The height of the middle and downstream buildings can evidently change the pollutant dispersion direction during the transport process. Within the polluted canyon, the pollutant dilution rate (PDR) also varies with different street canyon combinations. The highest PDR is observed when the upstream buildings are both low buildings no matter the height of downstream building. However, the two cases are likely to contribution pollution to the downstream canyon. The H-L-H combination is mostly against local pollution remove, while the L-H-L case is considered the best optimistic building combination with both the ability of diluting local pollution and not remarkably decreasing air quality of downstream canyon. The current work is expected instructive for city designers to optimize traffic patterns under typical existing geometry or in the development of urban geometry modification for air quality control. [ABSTRACT FROM AUTHOR]

Photon Activation Analysis (PAA) of environmental, archaeological and industrial samples requires extensive data analysis that is susceptible to error. For the purpose of saving time, manpower and minimizing error, a computer program was designed, built and implemented using SQL, Access 2007 and asp.net technology to automate this process. Based on the peak information of the spectrum and assisted by its PAA library, the program automatically identifies elements in the samples and calculates their concentrations and respective uncertainties. The software also could be operated in browser/server mode, which gives the possibility to use it anywhere the internet is accessible. By switching the nuclide library and the related formula behind, the new software can be easily expanded to neutron activation analysis (NAA), charged particle activation analysis (CPAA) or proton-induced X-ray emission (PIXE). Implementation of this would standardize the analysis of nuclear activation data. Results from this software were compared to standard PAA analysis with excellent agreement. With minimum input from the user, the software has proven to be fast, user-friendly and reliable. [ABSTRACT FROM AUTHOR]

In this paper, counter-current gas—liquid two-phase flow and onset of flooding in vertical narrow rectangular channels were studied. The onset of flooding in vertical narrow rectangular channels was investigated by the condition at which the liquid on the channel wall begins to move partially above the liquid injection section. In order to study the flow pattern, during counter-current flow and determine conditions associated with the onset of flooding, the flow pattern and pressure drop were investigated by visual experiments. In addition, the flooding phenomena in vertical narrow rectangular channels were compared with that in conventional channels. The results show that the flow characteristics and the tendency of pressure drop in vertical narrow rectangular channels were similarly with the conventional channels. However, the maximum of pressure drop appeared at the completed carrying up of flooding in vertical narrow rectangular channels, and it appeared at the onset of flooding in conventional channels. [ABSTRACT FROM AUTHOR]

Based on the flexural torsional guided wave theory and its focusing technique, this paper demonstrates the defect detection capability of flexural torsional guided waves on multiple defects with different shapes and axial, circumferential locations in pipe. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The design of addendum surfaces in sheet forming process is very important for the product quality, but it is very time-consuming and needs tedious trial-error corrections. In this paper, we propose a methodology to automatically generate the addendum surfaces and then to optimize them using a forming modelling solver. The surfaces’ parameters are taken as design variables and modified in course of optimization. The finite element mesh is created on the initial addendum surfaces and mapped onto the modified surfaces without remeshing operation. The Feasible Sequential Quadratic Programming (FSQP) is adopted as our algorithm of optimization. Two objective functions are used: the first one is the thickness function to minimize the thickness variation on the workpiece ; the second one is the appearance function aiming to avoid the scratching defects on the external surfaces of panels. The FSQP is combined with our “Inverse Approach” or “One Step Approach” which is a very fast forming solver. This leads to a very efficient optimization procedure. The present methodology is applied to a square box. The addendum surfaces are characterised by four geometrical variables. The influence of optimization criteria is studied and discussed. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Non-axisymmetric guided waves including flexural longitudinal and flexural torsional modes have shown natural focusing characteristics in pipe inspection. A flexural torsional mode theory was developed in this paper based on flexural longitudinal mode theory. Flexural mode experiments were then carried out to show the natural focusing phenomena. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The present paper investigates the characteristics of the supersonic turbulent flow in a wavy channel by direct numerical simulations. The Mach number, based on the bulk velocity and sound speed at the wall, is 1.5 and the Reynolds number, based on the bulk velocity, the channel half-width and the kinetic viscosity at the wall is 3 460. The wave amplitude to wavelength ratio is 0.05. To validate the numerical algorithms, a weak compressible flow at Mam = 0.33 is also simulated and the results agree well with available experimental measurements and results of DNS. The statistic quantities and flow structures for the supersonic flow are compared with those for the low Mach number case. It is found that, the statistic quantities profile for supersonic flow differs substantially from profile for the incompressible case as the appearance of the shock waves and their interaction with the turbulent flow field. [ABSTRACT FROM AUTHOR]

We briefly review the recent progresses in the new unitarization approach being developed by us. Especially we discuss the large Nc ππ scatterings by making use of the partial wave S matrix parametrization form. We find that the σ pole may move to the negative real axis on the second sheet of the complex s plane, therefore it raises the interesting question that this ‘σ’ pole may be related to the σ in the linear σ model. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

In the intermediate temperature region, an external ac bias induced expansion of dynamic voltage band (DVB) is investigated experimentally in a weakly coupled GaAs/AlAs superlattice. The observed results are explained based on an analysis of general nonlinear dynamics. It suggests that the effect of an external ac bias is to tighten the unstable limit cycle onto the stable fixed point. Beyond a certain critical value, the stable limit cycle is the only stable solution of the system resulting in the observation of self-sustained current oscillation. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

The phased array focusing technique is being developed with the intent to inspect hundreds of feet of pipeline from a single array position. The single array position is beneficial if access to a pipe is limited, e.g. steam pipes onboard U.S. Naval ships, nuclear power plants, oil and gas pipelines, etc. From a single array position, ultrasonic guided waves propagate down the length of the pipe and return information about potential defects. Focusing the ultrasonic energy at a predetermined location along the length of the pipe enhances the ability to detect defects that current state of the art inspection systems cannot detect. In this paper, theoretical time delays are used to focus torsional ultrasonic guided waves in the frequency ranges of 30 to 130 kHz and 200 to 800 kHz. Results of the focusing experiments are presented along with some concluding remarks and future work. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Forced two-phase flow boiling heat transfer coefficients of methane through a smooth horizontal tube with an inner diameter of 6 mm were measured. Experimental investigations were carried out at a particular set of test variables with the pressure range from 0.3 MPa to 0.6 MPa, heat flux range from 5 kW/m² to 63 kW/m², mass flux from 110 kg/m²-s to 275 kg/m²-s, and the vapor quality from 0 to 0.25.The influences of different experimental parameters on the flow boiling heat transfer coefficient were discussed. The data were also compared against ten heat transfer coefficient predictive methods. The correlations suggested by Kew-Conwell and Lazarek-Black both show good agreements with a mean absolute relative deviation less than 10%, and over 95% points within an error bandwidth of ±30.0%. [ABSTRACT FROM AUTHOR]

Precision forming of complex components of difficult-to-deform material, which satisfies the increasing demands of high performance and light weight in aerospace industries, has become a research frontier in advanced plastic forming domains. Owning to the usage of difficult-to-deform materials and hard-to-form complex structure, and the requirement of excellent service performance, significant unequal deformation takes place during plastic forming of such components, which would increase the forming load, produce forming defects, deteriorate the service performance and make the control and optimization of the forming process difficult. How to coordinate and control the unequal deformation is the key problem urgently to be solved. The through-process multi-scale modeling and simulation are essential for developing control method of unequal deformation. To this end, a through-process multi-scale modeling strategy was proposed in the present work. It is composed of a microscale cellular automaton model which predicts the microstructural morphology development, a mesoscale crystal plasticity model which characterizes the mechanism of unequal deformation, a coupled macro-microscale internal state variable model which predicts the constitutive behavior and microstructure evolution of the material, and a macroscale finite element model which predicts the forming regulations and defects. The strategy was applied to the isothermal local loading forming of large-scale complex titanium alloy component. The obtained results can guide the integrated forming of shape and performance in manufacturing complex components of difficult-to-deform material. [ABSTRACT FROM AUTHOR]

Two-proton emissions from the excited states of 17,18Ne and 28,29S were investigated by the radioactive beams bombarding on the 197Au target via the Coulomb excitation. The complete-kinematics measurements were actualized by the stacks of silicon-strip detectors and CsI+PIN array detectors. The invariant mass of final systems as well as the relative momentum, opening angle, and relative energy of the two emitted protons were reconstructed under the framework of relativistic kinematics. The mechanisms of two-proton emission were analyzed in a simple schematic model. With the help of Monte-Carlo simulations, the two protons emitted from the 6.15 MeV excited state of 18Ne and the excited states around 10 MeV of 29S, respectively, exhibit prominent features of 2He decay. While for the other states, no obvious diproton emissions were observed. [ABSTRACT FROM AUTHOR]

With the commissioning of HIRFL-CSR, HIRFL can provide heavy ion beams with energy covering the range of several MeV/u to 1 GeV/u. In this talk, the experiments on nuclear physics at different energies to be carried out with different experimental setups at HIRFL will be introduced. [ABSTRACT FROM AUTHOR]

The particle distribution on the ceramic filter surface has great effect on filtration performance. The numerical simulation method is used to analyze the particle distribution near the filter surface under different operation conditions. The gas/solid two-phase flow field in the ceramic filter vessel was simulated using the Eulerian two-fluid model provided by FLUENT code. The user-defined function was loaded with the FLUTNT solver to define the interaction between the particle and the gas near the porous ceramic candle filter. The distribution of the filter cake along the filter length and around the filter circumference was analyzed. The simulation results agree well with experimental data. The simulation model can be used to predict the particle distribution and provide theory direction for the engineering application of porous ceramic filters. [ABSTRACT FROM AUTHOR]

The experiments of two-proton emission from 29S and 17Ne excited levels were performed at HIRFL-RIBLL facility of Institute of Modern Physics, Lanzhou. Complete kinematics measurements were achieved by the detectors of silicon strip and CsI+PIN array after the 197Au target. The preliminary results show the strong correlation of two protons according to the spectrum of correlated proton-proton energies in the laboratory reference frame. [ABSTRACT FROM AUTHOR]

An internal and an external target experiment, ETE and HPLUS, respectively, will be built at the HIRFL-CSRm complex covering various nuclear physics programs. This talk introduces briefly the conceptual designs and the main physical interests of these two experiments. Parallel R&D works for the sub-detectors of ETE and HPLUS have been started. The current status is documented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

An experiment of 29S bombarding on 12C target was performed to study the phenomena of two-proton halo and two-proton emission. The 1p and 2p removal cross sections for 29S are 3.15±0.32 b and 1.85±0.20 b, respectively. The 2p removal cross section is abnormally large. It denotes the two-proton occurs to be a halo distribution. Among the 2p-27Si coincident events, a strong correlation between two protons was found. The small correlation angle indicates these two protons might come from 2He cluster emission. Moreover, the relative momentum distribution shows the two protons locate originally at singlet 2s state and emit with strong interaction. [ABSTRACT FROM AUTHOR]

The article presents an abstract on the theory and experiments of femtosecond stimulated Raman spectroscopy.