无机闪烁体性能测试方案研究

为满足诸如大型对撞机实验探测器研制、空间载荷量能器等大科学工程和新型医疗影像设备TOF-PET对闪烁体的筛选需求,对闪烁体的闪烁性能(发射光谱、光输出、能量分辨率、衰减时间、余辉以及符合时间分辨率等)进行了研究,并针对不同闪烁体样品的测试需求设计了一整套完整的无机闪烁体性能测试方案。在发射光谱测试中选择了不同的激发源进行对比测试,对能量分辨率与符合时间分辨等闪烁性能的测试条件进行优化,并成功应用于热门闪烁体掺杂铈的硅酸钇镥(LYSO: Ce)和钆铝镓石榴石(GAGG: Ce)的性能研究中,取得了较好的测试结果。     

Exposure rate by the spectrum dose index method using plastic scintillator detectors

The spectrum dose index (SDI) method was tested for use with data from plastic scintillator detectors by irradiating a typical portal detector system using different gamma sources and natural background. Measurements were compared with exposure rates simultaneously measured using a calibrated pressurised ion chamber. It was found that a modified SDI algorithm could be used to calculate exposure rates for these detectors despite the lack of photopeaks in plastic scintillator spectra.     

Synthesis of volatile inorganic hydrides by electrochemical method

Published data and results of our investigations on the problem of electrochemical synthesis of arsenic, phosphorus, and germanium hydrides are generalized. The results of the developments of the physicochemical bases of arsine synthesis by electrochemical reduction of arsenic acid, phosphine by reduction of white phosphorus in organic solvents, and monogermane by reduction of germanate in basic conditions are reported. The current yield of hydrides is 95, 90, and 40%, respectively. The promising guidelines of the practical use of electrochemical methods of the synthesis of the hydrides in the manufacture of semiconductor materials for microelectronics, optics, and laser engineering are discussed. The development of an arsine generator attracts considerable interest, which can serve as a basis for an aggregative continuous apparatus used in complex flow charts of manufacture of semiconductor materials.     

Non-linear steady state vibration of frames by finite element method

A finite element method based on the virtual work principle to determine the steady state response of frams in free or forced periodic vibration is introduced. The axial and flexural deformations are coupled by mean of the induced axial force along the element. The spatial discretization of the deformations is achieved by the usual finite element method and the time discretization by Fourier coefficients of the nodal displacements. No unconventional element matrices are needed. After applying the harmonic balance method, a set of non-linear algebraic equations of the Fourier coefficients is obtained. These equations are solved by the Newtonian iteration method in terms of the Fourier coefficient increments. Nodal damping can easily be included by a diagonal damping matrix. The direct numerical determination of the Fourier coefficient increments is difficult owing to the presence of peaks, loops and discontinuities of slope along the amplitude-frequency response curves. Parametric construction of the response curves using the phase difference between the response and excitation is recommended to provide more points during the rapid change of the phase (i.e. at resonance). For undamped natural vibration, the method of selective coefficients adopted. Numerical examples on the Duffing equation, a hinged–hinged beam, a clamped–hinged beam, a ring and a frame are given. For reasonably accurate results, it is shown that the number of finite elements must be sufficient to predict at least the linear mode at the frequency of interest and the number of harmones considered must satisfy the conditions of completeness and balanceability, which are discussed in detail.     

A steady rotational plane gas flow problem by hodograph method

The geometry and the solutions are investigated for steady rotational plane gas flows with arbitrary equation of statt when the velocity magnitude is constant along each individual streamline by using the hodographic technique.     

A hybrid integral-equation method for steady two-dimensional ship waves

This paper presents a novel integral-equation technique for solving the steady-state wave-resistance problem. The free-surface condition is linearized, but the body condition is satisfied exactly. An integral relation describing the flow inside an arbitrarily truncated internal region is first obtained by applying Green's Theorem, using only the simple source function for an infinite fluid. The internal flow is next matched with eigen expansions in the upstream and downstream outer regions. The radiation condition can be satisfied exactly simply by a proper choice of the solution form in these outer regions. The method is applied to investigate flows about both lifting and non-lifting two-dimensional bodies. Agreement with existing results is excellent. The present formulation provides a simple yet rational basis for tackling the practical three-dimensional ship-wave problem, in which past workers have encountered considerable difficulties using a complicated free-surface Green function.     

An improved steady inverse method for turbomachinery aerodynamic design

An improved inverse method for turbomachinery design is developed in this paper. A strict ‘no-slip’ boundary condition is imposed during the flow time marching process, and a virtual movement velocity is computed based on characteristics boundary conditions according to the difference of specified and calculated pressure loading, then the camber line of the blade is moved accordingly. A new ‘inverse’ time step calculation method is proposed to make the value of the ‘inverse’ time step case-independent, and a coupled non-uniform rational B-spline (NURBS) smoothing technique is used to improve the robustness of the solver, also guarantee the manufacturability of the obtained blade. Two-dimensional test cases, including compressor and turbine cascades, are adopted to validate the method. Then, the method is extended to three dimensions, and a high-loaded rotor of a fan stage is redesigned by the method in a stage environment. The final results indicate a fairly large performance gain, which demonstrates the effectiveness of the improved method.     

A hybrid element method for steady linearized free-surface flows

It is first shown that the two-dimensional linearized ship wave problem can be recast as the sum of a radiation and a diffraction problem for simple harmonic waves. Each problem can be solved by a hybrid element method (HEM) where conventional finite elements are used near the body and analytical solutions are used in the remaining infinite regions (super-elements). Variational principles which incorporate the matching conditions between regular and super-elements as natural conditions are derived. Numerical examples are presented. The theoretical aspects for extending the above ideas to a three-dimensional ship wave problems are also described.     

A boundary element method for steady incompressible thermoviscous flow

A boundary element formulation is presented for moderate Reynolds number, steady, incompressible, thermoviscous flows. The governing integral equations are written exclusively in terms of velocities and temperatures, thus eliminating the need for the computation of any gradients. Furthermore, with the introduction of reference velocities and temperatures, volume modelling can often be confined to only a small portion of the problem domain, typically near obstacles or walls. The numerical implementation includes higher order elements, adaptive integration and multiregion capability. Both the integral formulation and implementation are discussed in detail. Several examples illustrate the high level of accuracy that is obtainable with the current method.