Cold and stable antimatter for fundamental physics

The field of cold antimatter physics has rapidly developed in the last 20 years, overlapping with the period of the Antiproton Decelerator (AD) at CERN. The central subjects are CPT symmetry tests and Weak Equivalence Principle (WEP) tests. Various groundbreaking techniques have been developed and are still in progress such as to cool antiprotons and positrons down to extremely low temperature, to manipulate antihydrogen atoms, to construct extremely high-precision Penning traps, etc. The precisions of the antiproton and proton magnetic moments have improved by six orders of magnitude, and also laser spectroscopy of antihydrogen has been realized and reached a relative precision of 2 × 10⁻¹² during the AD time. Antiprotonic helium laser spectroscopy, which started during the Low Energy Antiproton Ring (LEAR) time, has reached a relative precision of 8 × 10⁻¹⁰. Three collaborations joined the WEP tests inventing various unique approaches. An additional new post-decelerator, Extra Low ENergy Antiproton ring (ELENA), has been constructed and will be ready in 2021, which will provide 10–100 times more cold antiprotons to each experiment. A new era of the cold antimatter physics will emerge soon including the transport of antiprotons to other facilities.     

The basis step in the construction of the principle of mathematical induction based on APOS theory

Using APOS theory as the framework along with a case study from a perspective within the methodological design of APOS theory, this study presents a cognitive model of the Principle of Mathematical Induction (PMI) in higher education. Based on evidence from university classrooms and the result of an initial measurement, the genetic decomposition designed by Dubinsky and Lewin for this concept was reformulated, introducing and defining the basis step in the PMI as a mental process. Using this reformulated genetic decomposition, the productions of four university students are analysed in order to support or refute the constructions it proposes. The results show that the reformulated genetic decomposition is viable and that the inclusion of the basis step as a mental process was seen in the cognitive model of the PMI shown by the students. The instruments used provide activities for a teaching sequence for the PMI at university level.     

Classification of time-of-flight secondary ion mass spectrometry spectra from complex Cu–Fe sulphides by principal component analysis and artificial neural networks

Artificial neural network (ANN) and a hybrid principal component analysis-artificial neural network (PCA-ANN) classifiers have been successfully implemented for classification of static time-of-flight secondary ion mass spectrometry (ToF-SIMS) mass spectra collected from complex Cu–Fe sulphides (chalcopyrite, bornite, chalcocite and pyrite) at different flotation conditions. ANNs are very good pattern classifiers because of: their ability to learn and generalise patterns that are not linearly separable; their fault and noise tolerance capability; and high parallelism. In the first approach, fragments from the whole ToF-SIMS spectrum were used as input to the ANN, the model yielded high overall correct classification rates of 100% for feed samples, 88% for conditioned feed samples and 91% for Eh modified samples. In the second approach, the hybrid pattern classifier PCA-ANN was integrated. PCA is a very effective multivariate data analysis tool applied to enhance species features and reduce data dimensionality. Principal component (PC) scores which accounted for 95% of the raw spectral data variance, were used as input to the ANN, the model yielded high overall correct classification rates of 88% for conditioned feed samples and 95% for Eh modified samples.     

A simple and effective scheme for data reduction of stress relaxation incorporating physical-aging effects: An analytical and numerical analysis

A simple methodology for obtaining viscoelastic parameters from the stress relaxation tests incorporating physical-aging effects is presented. The method assumes that the experimental data are in the linear viscoelastic domain. Three different mathematical representations of the viscoelastic stress relaxation modulus are analysed and used. Experimental data obtained from literature and simulated data with a random error are used to evaluate the proposed methodology. It is proved that it can capture very well the relaxation modulus of polymers irrespective of the mathematical representation used for the relaxation modulus. Moreover, the methodology proved to be reasonably insensitive to random noise. Extrapolation predictions were also evaluated for the proposed models with very good results.     

分析化学中常用有机试剂的分子结构式及作用原理

Due to the fact that the molecular structure has been removed from most of the analytical chemistry textbook of recent editions, this paper collected more than 90 organic reagents from three classic text books, categorized these molecules according to the application, and analyzed the molecular structure and the mechanism of functions in applications.     

Channel reduction schemes for fiber-optic angle encoders

Three fiber-optic sensor systems designed to remotely determine angular position that achieve high angular resolution with fewer channels than comparable Gray code encoders are described. Two of the Systems use a sheet polarizer affixed to a “codewheel” and the third system uses a two-channel digital shaft encoder style “codewheel.”

The first polarization scheme uses four optical channels, two of which are analog and two digital. The ratio of the two analog channel intensities yields tan²θ. The fourfold quadrant ambiguity is resolved by the two digital channels that are transected by two semicircular masks on the polarizer codewheel (Ref. U.S. Patent No. 4,577,414, 25 Mar 1986). The second polarization scheme again uses quadrant ambiguity masks but employs only one analog channel that simulates a polarization vector that oscillates through 90°. The oscillating vector is produced by the superposition of two sine-wave-modulated beams at the polarizer codewheel. The modulations of the two beams have a phase difference that is created by time delaying one of the beams in a fiber delay loop. The phase difference between the generated composite signal and a reference signal then determines the angle of the codewheel. We have demonstrated experimentally that this type of split analog-digital scheme has a resolution equivalent to a 10-bit digital system (i.e., ±0.35°) independent of codewheel diameter.

The serial digital shaft encoder scheme uses only two digital channels and a codewheel that has two concentric masks with 48 equally spaced windows offset with respect to each other by one-half window width. At 0° there is a unique mask that initializes an up/down decoder chip (Hewlett-Packard HCTL-2000). This system has a resolution better than 7 bits using a 5-cm diameter code wheel and 1-mm Selfoc^TM lenses.

The supporting electro-optical systems including sources, fibers, lenses, mirrors, couplers, WDMs, polarizers, detectors, and signal processing for all schemes are described and the relative merits of each are compared.     

Haudorff测度与等径不等式

对于:Hausdorff维数为s>0的满足开集条件的自相似集E(?)Rn(n>1),我们引入等径不等式Hs|E(X)≤|X|s,以及使该不等式等号成立而直径大于0的极限集U(?)Rn.这里,Hs|E(·)是限制到集合E上的s维Hausdorff测度,而|X|指集合X在欧氏度量下的直径.当s=n时,n维球是唯一的极限集;当s∈(1,n)时,除去一些反面例子以外,我们对上述等径不等式的极限集的基本性质所知甚少.可以看出,这些不等式与Hs(E)的准确值的计算有密切联系.作为特例,我们将考虑Sierpinski垫片,指出计算这一典型自相似集的In2/In3维Hausdorff测度准确值的困难何在.由此可以大致推想,为什么除去平凡情形以外,至今还没有一个具体的满足开集条件而维数大于1的自相似集的:Hausdorff测度准确值被计算出来.     

Entropic Formulation of Statistical Mechanics

We present an alternative formulation of Equilibrium Statistical Mechanics which follows the method based on the maximum statistical entropy principle in Information Theory combined with the use of Massieu–Planck functions. The different statistical ensembles are obtained by a suitable restriction of the whole set of available microstates. The main advantage is that all of the equations that relate the average values with derivatives of the partition function are formally identical in the different ensembles. Moreover, Einstein's fluctuation formula is also derived within the same framework. This provides a suitable starting point for the calculation of fluctuations of extensive and intensive variables in any statistical ensemble.     

Beyond Causal Explanation: Einstein’s Principle Not Reichenbach’s

Our account provides a local, realist and fully non-causal principle explanation for EPR correlations, contextuality, no-signalling, and the Tsirelson bound. Indeed, the account herein is fully consistent with the causal structure of Minkowski spacetime. We argue that retrocausal accounts of quantum mechanics are problematic precisely because they do not fully transcend the assumption that causal or constructive explanation must always be fundamental. Unlike retrocausal accounts, our principle explanation is a complete rejection of Reichenbach’s Principle. Furthermore, we will argue that the basis for our principle account of quantum mechanics is the physical principle sought by quantum information theorists for their reconstructions of quantum mechanics. Finally, we explain why our account is both fully realist and psi-epistemic.