Experimental observation of permanent magnet rotation

Why does the Earth rotate? At present, several theories on Earth rotation remain hypotheses. Hence, the aim of this study was to obtain experimental evidence of the relationship between the rotational force and magnetic field so that we can use experimental devices to demonstrate the rotation relationship among the planets and the sun. Each permanent magnet rotating under the action of an external force is installed on the shaft of DC motor; each magnetic ball designed to rotate in a magnetic field is placed in the center of a hollow sphere that can float on the water. Using the above setup, the experimental methods and procedures based on this research can be used to observe the rotation behaviour of a permanent magnet in a magnetic field, understand the reason for its rotation, and determine the strength of the rotational force of the permanent magnet in the magnetic field.

Behaviour of Steel Tubular Knee Joint in Aluminium Frames with Tension-Tie Element

Aluminium portal frames with a tension tie element are a commonly used type of aluminium structure. Due to the significant reduction in aluminium’s mechanical properties caused by welding, typical beam to column joints of such frames are formed using bolts and welded steel knee joints embedded in the structure. Expressions for the reliable assessment of the behaviour of such joints are lacking, thus limiting the use of aluminium portal frames. Although the behaviour of steel joints using hollow sections is well investigated, there are only a small number of studies regarding knee joints, none of which investigate the influence of the tie element on the joint behaviour. Therefore, the first stage of the research is focused on the flexural behaviour of steel knee joints with tension tie elements. Laboratory tests of three identical steel knee joints with a tension tie element were conducted as well as a parametric numerical study with variation of tie element stiffness. It was concluded that different stiffnesses of the tie element have little influence on moment–rotation behaviour of the knee joint, but greatly affect overall frame resistance to vertical loads. It was also concluded that different stiffnesses of the tie element can lead to different failure modes of the knee joint as well.

Evaluation of the Interstorey Drift Performance of Timber Beam-Hanger Connection Systems

This paper presents the results of a study on pre-engineered steel and aluminum, bolted-plate (BP), staggered dove-tail (S-DT), and dove-tail prototype (DTP) beam-hanger connection systems for glue-laminated timber joints under a combination of shear and reversed cyclic loading. A total of seven systems were tested to observe the evolution of damage, failure modes, and moment-rotation behaviour. The interstorey drift/deflection of a building that would cause failure of each system is inferred from the ultimate rotation capacities and compared to the limit(s) prescribed by Clause 4.1.8.13.3 of the National Building Code of Canada. The BP systems generally reached an interstorey drift exceeding 2.5%, while the S-DT and DTP systems reached drifts of 0.6% and >1.2%, respectively. The BP systems also exhibited more ductile failure modes than the S-DT and DTP systems, involving withdrawal failure of the wood screws. Recommendations are made for appropriate connectors to use in each building category considered.

Constraining the Einstein equivalence principle with multi-wavelength observations of polarized blazars

ABSTRACT In this paper, we present a novel method to test the Einstein equivalence principle (EEP) using (simultaneous) multi-wavelength radio observations of polarized blazars. We analyse simultaneous multi-wavelength polarization observations of 3C 279 at 22, 43, and 86 GHz obtained by two antennas of the Korean VLBI Network. We obtained 15 groups of polarization data, and applied the Metropolis–Hastings Markov chain (MHMC) to simulate the parameters when considering the EEP effect and the simplest form of Faraday rotation (single external Faraday screen). The final results show the constraint of the parametrized post-Newtonian (PPN) parameter γ discrepancy as Δγp = (1.91 ± 0.34) × 10−20. However, the single external Faraday screen is an oversimplification for blazars because there are numerous observations showing complex Faraday rotation behaviour for blazars due to internal/external Faraday dispersion, beam depolarization, etc. The Δγp results of this paper can only be considered as upper limits. Only if all other effects are revealed and considered should the result be taken as a direct measurement of the violation of the EEP.