Pipe internal grooving using closed magnetic field system: A novel method

The present work proposes an innovative method to form microgrooves on a tube's internal surface through new machining based on the principle of the closed magnetic circuit. A newly designed machine with a magnetic grooving tool was fabricated. The tool consists of a pair of magnets positioned in the pipe to be pulled by another pairing magnet set at the pipe's external side, arranged in sequence of N−S−N−S direction so that it creates a closed magnetic field that has a greater pulling force. By controlling the magnet pair at the pipe's external side in the linear and rotational direction, the magnetic grooving tool is moved in both directions and simultaneously pulled towards the pipe surface to form the microgrooves. The experiment was carried out by adjusting the magnet's size combination and its distance to vary the magnetic strengths. The grooving dimension was examined by using an optical microscope and analysed using a 3-dimensional laser profilometer surface analyser. With N52 class Nd₂Fe₁₂B neodymium (40×10×10 mm³), the maximum groove depth of 75.51 μm was recorded and the minimum depth of 2.33 μm was recorded by using magnet size 10×10×10 mm³. The method is capable to produce microgrooves on the copper pipe's internal surface.     

Spikernels: predicting arm movements by embedding population spike rate patterns in inner-product spaces

Inner-product operators, often referred to as kernels in statistical learning, define a mapping from some input space into a feature space. The focus of this letter is the construction of biologically motivated kernels for cortical activities. The kernels we derive, termed Spikernels, map spike count sequences into an abstract vector space in which we can perform various prediction tasks. We discuss in detail the derivation of Spikernels and describe an efficient algorithm for computing their value on any two sequences of neural population spike counts. We demonstrate the merits of our modeling approach by comparing the Spikernel to various standard kernels in the task of predicting hand movement velocities from cortical recordings. All of the kernels that we tested in our experiments outperform the standard scalar product used in linear regression, with the Spikernel consistently achieving the best performance.     

Cryptanalysis of an efficient three‐party password‐based key exchange scheme

Three‐party password‐authenticated key exchange (3PAKE) protocols allow entities to negotiate a secret session key with the aid of a trusted server with whom they share a human‐memorable password. Recently, Lou and Huang proposed a simple 3PAKE protocol based on elliptic curve cryptography, which is claimed to be secure and to provide superior efficiency when compared with similar‐purpose solutions. In this paper, however, we show that the solution is vulnerable to key‐compromise impersonation and offline password guessing attacks from system insiders or outsiders, which indicates that the empirical approach used to evaluate the scheme's security is flawed. These results highlight the need of employing provable security approaches when designing and analyzing PAKE schemes. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation of cellulose–graphene oxide aerogels with N‐methyl morpholine‐N‐oxide as a solvent

Cellulose–graphene oxide (GO) aerogel composites were successfully prepared from cellulose and GO dispersed in N‐methyl morpholine‐N‐oxide monohydrate, a nontoxic and environmentally friendly solvent, after a freeze‐drying process. Because of the strong interactions between the numerous oxygen‐containing groups located on the surface of GO and the functional groups of the cellulose molecules, the GO monolayers were well dispersed in the three‐dimensional porous structure of the cellulose aerogels. With the addition of 10 wt % GO, the swelling ratios and water contents of the composite cellulose–GO aerogels increased from 468 to 706% and from 82.4% to 87.6%, respectively. The corresponding maximum decomposition temperatures also increased from 335 to 353 °C with increasing GO content from 0 to 10%; this indicated that the thermal stability of the cellulose–GO aerogels was enhanced. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46152.