Holography and interferometry in photoelasticity

A physical explanation of photoelastic interferometry and holography is presented. Reasons for special properties and specific restrictions are argued in relation to this physical picture. The controlling intensity relationships for interferometry and holography are derived by simple physical analysis. The relationship between absolute retardation, isochromatic- and isopachic-fringe systems is clarified. Model material requirements for photoelastic interferometry and holography are shown to be identical.1971 William M. Murray Lecture was presented at 1971 SESA Fall Meeting held in Milwaukee, Wisc., On October 19–22.     

Displacement measurements around cracks in three-dimensional problems by a hybrid experimental technique

Diffraction gratings were applied to slices taken from three-dimensional stress-frozen models of bodies with cracks. The slices were then annealed to relax the reversible strains and moiré interferometry was used to determine the deformation of the slice. A virtual reference grating of 1200 ?/mm (30,000 ?/in.) was used to provide the required high sensitivity. The moiré pattern in the LEFM (linear-elastic fracture-mechanics) zone was photographed with 20 × magnification. Results were compared with those obtained photoelastically.     

Shear-strain contours from moiré interferometry

Whole-field contour maps of shear strains _xy are derived from displacement fields obtained by moiré interferometry with 2400 /mm (60,960 /in.). Cross-derivatives of displacements are obtained by mechanical differentiation. They are summed by graphical additive moiré. The high sensitivity of moiré interferometry permits quantitative analysis in the small-strain domain.Paper was presented at V International Congress on Experimental Mechanics held in Montreal, Quebec, Canada on June 10–15, 1984.     

Moiré method for in-plane and out-of-plane displacement measurements

A high-frequency phase grating on a specimen surface is illuminated by oblique beams. Recordings of two diffracted beams by holographic interferometry reveal the wavefront changesN _a andN _b. In-plane displacements are proportional toN _a?N_b, while out-of-plane displacements are proportional toN _a+N_b. Experimental corroboration is presented.     

High conduction neutron absorber to simulate fast reactor environment in an existing test reactor

A new metal matrix composite material has been developed to serve as a thermal neutron absorber for testing fast reactor fuels and materials in an existing pressurized water reactor. The performance of this material was evaluated by placing neutron fluence monitors within shrouded and unshrouded holders and irradiating for up to four cycles. The monitor wires were analyzed by gamma and X-ray spectrometry to determine the activities of the activation products. Adjusted neutron fluences were calculated and grouped into three bins—thermal, epithermal, and fast—to evaluate the spectral shift created by the new material. A comparison of shrouded and unshrouded fluence monitors shows a thermal fluence decrease of ~11 % for the shielded monitors. Radioisotope activity and mass for each of the major activation products is given to provide insight into the evolution of thermal absorption cross-section during irradiation. The thermal neutron absorption capability of the composite material appears to diminish at total neutron fluence levels of ~8 × 10²⁵ n/m². Calculated values for dpa in excess of 2.0 were obtained for two common structural materials (iron and nickel) of interest for future fast flux experiments.     

High resolution measurements of hyperfine structure and isotope shifts in 9 spectral lines of Nd I

Nine transitions in Nd I, originating from various levels belonging to the 4f ⁴6s ² ground state configuration, have been studied with high resolution using an actively stabilized C.W. ring dye laser in a crossed laser-atomic-beam set-up. Accurate values for the isotope shifts in all transitions as well as for the hyperfine structure constants of 7 excited states have been obtained.     

Interaction of hydrogen with indiumvacancy clusters in tungsten

Hydrogen trapping at specific¹¹¹In-vacancy complexes in tungsten was studied by means of perturbed angular correlations. The hydrogen was either implanted into the sample or diffused from the gas. We observed desorption of the trapped hydrogen in the temperature range 450–550 K.     

LED正向压降随温度的变化关系研究

分析了LED正向压降随温度变化的物理机理,建立了恒流驱动下正向压降随温度的变化系数测试系统对不同材料、不同发射波长的LED电压随温度变化系数进行了系统的实验研究,利用最小二乘法对实验数据进行了线性拟合,得到了不同发射波长的AlGaInP、InGaN材料LED的电压随温度变化系数,对超高亮度LED、功率型LED器件及系统的热工参数测量积累了的重要数据.     

Time asymmetries in classical and in nonclassical physics

A comparative study is made of the eigenvalue problems of electromagnetics and quantum mechanics, with special reference to the operations of spatial inversionP and time inversionT. Electromagnetics, which permits closer agreement with the dictates of relativity (when the latter is extended toP andT), exhibits characteristic differences with respect to quantum mechanics. An evaluation of these distinctions is presented against the backdrop of a choice between absolute scalar action and charge versus pseudoscalar action and charge.     

Boundary pairs associated with quadratic forms

We introduce a purely functional analytic framework for elliptic boundary value problems in a variational form. We define abstract Neumann and Dirichlet boundary conditions and a corresponding Dirichlet‐to‐Neumann operator, and develop a theory relating resolvents and spectra of these operators. We illustrate the theory by many examples including Jacobi operators, Laplacians on spaces with (non‐smooth) boundary, the Zaremba (mixed boundary conditions) problem and discrete Laplacians.