[en] A tube is often applied as an energy absorber in structures subject to impact loads. However, when several tubes are combined to absorb energy, how to arrange these tubes and match their dimensions has not been investigated. We provide a novel equivalent stiffness (ES) method for the initial design of tube-based energy absorbers, in which each tube is expressed by an equivalent spring with average post-buckling stiffness, and these springs are connected in series or parallel or hybrid. The plastic deformation and strain energy are distributed among them according to their relative ES value. The relationship between plastic energy and post-buckling stiffness is derived analytically and verified numerically. Finally, an application example is provided and the optimal tube arrangement and dimensions are obtained by combining the proposed ES method with an optimization code. The results demonstrate that this method can provide an initial design of tube-based energy absorbers efficiently.

[en] For any complex simple Lie algebra, we generalize the primary fields in the Wess-Zumino-Novikov-Witten conformal field theory for a case with irregular singularities. We refer to these generalized primary fields as confluent primary fields. We present the screening currents Ward identity, a recursion rule for computing the expectation values of the products of confluent primary fields. In the case of sl₂, the expectation values of the products of confluent primary fields are integral formulas of solutions to confluent Knizhnik-Zamolodchikov (KZ) equations given in Jimbo et al (2008 J. Phys. A: Math. Theor. 41 175205). By computing the operator product expansion of the energy-momentum tensor T(z) and the confluent primary fields, we obtain new differential operators. Moreover, in the case of sl₂, these differential operators are the same as those of the confluent KZ equations (Jimbo et al 2008).

[en] We construct confluent KZ equations with Poincare rank 2 at infinity for the case of sl_N and the integral representation for the solutions. Hamiltonians of these confluent KZ equations are derived from suitable quantization of dlog τ constructed in the theory of monodromy preserving deformation (MPD) in Jimbo et al (1981 Physica D 2 306-52). Our confluent KZ equations can be viewed as a quantization of MPD with Poincare rank 2 at infinity.

[en] In wireless network planning, large-scale MIMO can be applied to beam forming technology, which can ensure the continuous signal of user receiver without interruption. When the user moves, beamforming technology requires beamswitching to reposition the user, which increases unnecessary overhead. In this paper, the user azimuth beam tracking algorithm based on Kalman filtering decomposed the user’s trajectory in the actual scene, and used Kalman filtering algorithm to track the decomposed user’s trajectory, so that the beam can be adjusted to point to the user in real time. Through experimental verification, Kalman filtering is relatively accurate in predicting the position of mobile users relative to the Angle information of base station, and the predicted beam can ensure the stability of users’ connection, and at the same time achieve the purpose of reducing the number of beam-to-beam switching, reducing the overhead, improving the beam tracking efficiency, and making the connection more stable. (paper)

[en] Photocatalytic decarboxylative cross-coupling which achieves the derivatization of widespread organic acids has become a hot topic in organic synthesis. As special acids, α-oxocarboxylicacids show the great potential in running decarboxylation to construct ketone derivatives. In this article, we have developed a photocatalytic decarboxylative cross-coupling of α-oxocarboxylicacids and olefins to the synthesis of diverse aryl ketones. Various alkenes and α-oxocarboxylicacids were compatible, generating the desired products in up to 90% yield. Preliminary mechanism studies suggest that a free radical pathway is involved in this process.

[en] To exploit the outstanding ability of carbon nanotubes to facilitate electron transfer in a microbial fuel cell (MFC) system, multi-wall carbon nanotube (MWNT) and polyeletrolyte polyethyleneimine (PEI) were employed to modify carbon paper (TP) electrode utilizing a layer-by-layer (LBL) assemble technique for the first time, and the performance of the modified electrode as an anode in MFC was investigated. This modification strategy ensured a relatively high content of MWNTs within the polymer matrix. IR and cyclic voltammetry (CV) demonstrated the uniform formation of a polyethyleneimine/MWNT multilayer composite on the TP surface. The SEM profiles presented a three-dimensional MWNTs interwoven network surface structure with a large accessible surface area. Electrochemical impedance spectroscopy (EIS) measurements confirmed that the existence of polyelectrolyte/MWNT multilayers decreased the interfacial charge transfer resistance from 1163 to 258 Ω. With the modified anode, the MFC produced a higher power density with 20% enhancement comparing to the bare TP anode. The MWNT-based LBL self-assembled electrode is promising for the electricity production by MFC.