Nondestructive Testing and Characterization of Residual Stress Field Using an Ultrasonic Method

To address the difficulty in testing and calibrating the stress gradient in the depth direction of mechanical components, a new technology of nondestructive testing and characterization of the residual stress gradient field by ultrasonic method is proposed based on acoustoelasticity theory. By carrying out theoretical analysis, the sensitivity coefficients of different types of ultrasonic are obtained by taking the low carbon steel（12%C） as a research object. By fixing the interval distance between sending and receiving transducers, the mathematical expressions of the change of stress and the variation of time are established. To design one sending-one receiving and oblique incidence ultrasonic detection probes, according to Snell law, the critically refracted longitudinal wave（LCR wave） is excited at a certain depth of the fixed distance of the tested components. Then, the relationship between the depth of LCR wave detection and the center frequency of the probe in Q235 steel is obtained through experimental study. To detect the stress gradient in the depth direction, a stress gradient LCR wave detection model is established, through which the stress gradient formula is derived by the relationship between center frequency and detecting depth. A C-shaped stress specimen of Q235 steel is designed to conduct stress loading tests, and the stress is measured with the five group probes at different center frequencies. The accuracy of ultrasonic testing is verified by X-ray stress analyzer. The stress value of each specific depth is calculated using the stress gradient formula. Accordingly, the ultrasonic characterization of residual stress field is realized. Characterization results show that the stress gradient distribution is consistent with the simulation in ANSYS. The new technology can be widely applied in the detection of the residual stress gradient field caused by mechanical processing, such as welding and shot peening.

On Unobservability of One-Way Speed of Light

In this paper we recall the different definitions of simultaneity, the coordinate time interval and the velocity. It is emphasized that the above second two definitions depend on the simultaneity. We review the test theories on special relativity. It is shown that anisotropy (if possible) of one-way speed of light has not any ef- fects in the physical experiments. Therefore anisotropy of one-way speed of light cannot be determined by the experiments, except if an absolute (standard) simultaneity would be found.

EXPERIMENTAL TESTS OF GRAVITATIONAL THEORY

Revised September 2013 by T. Damour （IHES, Bures-sur-Yvette, France）. Einstein＇s General Relativity, the current ＂standard＂ theory of gravitation, describes gravity as a universal deformation of the Minkowski metric：

Non-Probabilistic Approach to the Time of Energy Emission in Small Quantum Systems

The energy emitted by an electron in course of its transition between two quantum levels can be considered as a dissipated energy. This energy is obtained within a definite interval of time. The problem of the size of the time interval necessary for transitions is examined both on the ground of the quantum approach as well as classical electrodynamics. It is found that in fact the emission time approaches the time interval connected with acceleration of a classical velocity of the electron particle from one of its quantum levels to a neighbouring one.

Evaluation of A Scale of Patient-Reported Outcomes for the Assessment of Myasthenia Gravis Patients in China

Objective： To evaluate a scale of patient-reported outcomes for the assessment of myasthenia gravis patients （MG-PRO） in China. Methods： A total of 100 MG patients were interviewed for the field testing. Another 56 MG patients were selected and assessed with the MG-PRO scale before treatment and at 1, 2 and 4 weeks after treatment. The classical test theory and item response theory （IRT） were used to assess the psychometric characteristics of the MG-PRO scale, Results： The MG-PRO scale included 4 dimensions： physical, psychological, social environment, and treatment. Confirmatory factor analysis showed that each dimension was consistent with the theoretical construct. The scores of the physical and psychological dimensions increased significantly at 1 week after treatment （P〈0.05）. All the dimension scores and the MG-PRO score increased significantly at 2 and 4 weeks after treatment （P〈0.05）. IRT showed that person separation indices were greater than 0.8, most of the item fit residual statistics were within ＋ 2.5, and no item had uniform or non-uniform differential item functioning （DIF） between gender and age （〈40, 〉140）. Conclusions： The MG-PRO scale is valid for measuring the quality of life （QOL） of MG patients, with good reliability, validity, responsiveness, and good psychometric characteristics from IRT. It can be applied to evaluate the QOL of MG patients and to assess treatment effects in clinical trials.

Fighting and aggressive sound determines larger male to win male-male competition in a bark beetle

Intrasexual selection occurs in male-male competition over access to females and usually results in the larger male winning.While much research has documented that size matters,little is known about how the larger male wins.Dendroctonus vale ns is an aggregating monogamous bark beetle in which males have large variation in body size and display intense competition over females.Behavioral observation showed two males fight each other within the gallery by pushing/shoving and stridulated more when two males encountered each other.Experiments using two different-sized males synchronously competing showed that larger males won 95%of contests.Reciprocal displacement experiments using muted and intact males of different or equal size were used to simulate male-male competition.Larger males displaced the smaller resident male in 90%of contests,while smaller males prevailed over larger residents in 6.7%of contests.With both males silenced,larger males displaced smaller males in 80%of con tests,while smaller males prevailed in 8%of con tests.Further experiments using equal-sized males showed aggressive soundemitting males displaced muted males in 67%of contests,yet intact males displaced other intact males in only 37.5%of con tests.Sound analysis showed sound pressure level is an honest signal of body size and males chose soft sounds over loud aggressive sounds in assays.Therefore,D.valens males have evolved dual behaviors,fighting and aggressive sounds associated with body size,to assess rivals to compete for a partner,gaining insights in male-male competition for this species and for other animals.