Spatiotemporal data mining: a survey on challenges and open problems

Spatiotemporal data mining (STDM) discovers useful patterns from the dynamic interplay between space and time. Several available surveys capture STDM advances and report a wealth of important progress in this field. However, STDM challenges and problems are not thoroughly discussed and presented in articles of their own. We attempt to fill this gap by providing a comprehensive literature survey on state-of-the-art advances in STDM. We describe the challenging issues and their causes and open gaps of multiple STDM directions and aspects. Specifically, we investigate the challenging issues in regards to spatiotemporal relationships, interdisciplinarity, discretisation, and data characteristics. Moreover, we discuss the limitations in the literature and open research problems related to spatiotemporal data representations, modelling and visualisation, and comprehensiveness of approaches. We explain issues related to STDM tasks of classification, clustering, hotspot detection, association and pattern mining, outlier detection, visualisation, visual analytics, and computer vision tasks. We also highlight STDM issues related to multiple applications including crime and public safety, traffic and transportation, earth and environment monitoring, epidemiology, social media, and Internet of Things.

     

Observer design for induction motor: an approach based on the mean value theorem

In this paper, observer design for an induction motor has been investigated. The peculiarity of this paper is the synthesis of a mono-Luenberger observer for highly coupled system. To transform the nonlinear error dynamics for the induction motor into the linear parametric varying (LPV) system, the differential mean value theorem combined with the sector nonlinearity transformation has been used. Stability conditions based on the Lyapunov function lead to solvability of a set of linear matrix inequalities. The proposed observer guarantees the global exponential convergence to zero of the estimation error. Finally, the simulation results are given to show the performance of the observer design.     

Synthesis and corrosion inhibition evaluation of a new schiff base hydrazone for mild steel corrosion in HCl medium: electrochemical,DFT, and molecular dynamics simulations studies

Abstract

The development of cost-effective, sustainable, eco-friendly and efficient compounds is a renovated science and a demanding assignment for today’s chemists and technology specialists. In this context, the anticorrosion effect of a new Schiff base hydrazone, namely (E)-2-(4-(2-(methyl(pyridin-2-yl)amino)ethoxy)benzylidiene)hydrazine-1-carboxamide (MPAH) against the mild steel (MS) surface in 1.0?M HCl has been analyzed utilizing experimental methods, thermodynamic characterizations, and computational studies. MPAH has proven to be an effective inhibitor in 1.0?M HCl solution. Its inhibition performance improved by raising the concentration of the compound to an optimal concentration of 5?×?10^?3 M, and 97% efficiency was achieved at 303?K. Inhibitor adsorption on the MS has been explicated with both physical and chemical interactions. The adsorption was in accordance with the isotherm of Langmuir. The impact of MPAH on the surface of MS had been confirmed utilizing SEM/EDX, electrochemical impedance spectroscopy (EIS), gravimetric measurements (WL), and potentiodynamic polarization (PDP). The adsorption of the studied compound on the MS surface has also been investigated by DFT and the molecular dynamics (MD) simulations.     

Uniform Stabilization of aNonlinear Axially Moving String by a Boundary Control of Memory Type

A nonlinear problem modeling a moving string with memory condition at the boundary is considered. This work aims at establishing reasonable sufficient conditions capable of suppressing the transversal vibrations that occur during the movement of the string. Unlike the fixed strings case here we need to employ the Reynold Transport Theorem to compute the ”total” derivative. This results in the appearance of several boundary terms which necessitates appropriate handling. We shall prove that the motion of the string plays an important role in determining the rate of the decay of solutions.     

Single step fabrication of N-doped graphene/Si3N4/SiC heterostructures

In-plane heteroatom substitution of graphene is a promising strategy to modify its properties. The ability to dope graphene with electron-donor nitrogen heteroatoms is highly important for modulating electrical properties of graphene. Here we demonstrate a transfer-free method to directly grow large area quasi free-standing N-doped graphene bilayers on an insulating substrate （Si3N4）. Electron-bombardment heating under nitrogen flux results in simultaneous growth of N-doped graphene and a Si3N4 layer on the SiC surface. The decoupling of N-doped graphene from the substrate and the presence of Si3N4 are identified by X-ray photoemission spectroscopy and low-energy electron diffraction. The substitution of nitrogen atoms in the graphene planes was confirmed using high resolution X-ray photoemission spectroscopy which reveals several atomic configurations for the nitrogen atoms： Graphitic-like, pyridine-like, and pyrrolic- like. Furthermore, we demonstrated for the first time that N-doped graphene could be used to efficiently probe oxygen molecules via nitrogen atom defects.     

An accurate time-to-digital converter based on a self-timed ring oscillator for on-the-fly time measurement

This paper proposes a new architecture of a time-to-digital converter (TDC) based on a self-timed ring (STR) oscillator with sub-gate delay resolution. The proposed TDC can virtually achieve as fine as desired time resolution by simply increasing its number of stages thanks to the STR unique features. Exploiting the phase difference between events propagating in the same STR without collision, this TDC benefit from a uniform phase distribution. Thus, under certain conditions, a regular time base can be generated and a compact readout algorithm can be applied. Moreover, the proposed technique allows on-the-fly time measurement on fast non-periodic signals. As a proof-of-concept, an STR-based TDC with only 9-stages has been simulated using 28 nm FDSOI technology. A time resolution of 8.9 ps has been achieved. Without using calibration, the measured DNL and INL are 0.44 and 0.40 LSB, respectively. Simulation results point out the advantage of this TDC in terms of measurement accuracy and state the limit of the on-the-fly measurement according to the dependency between the jitter and the time resolution.     

Functional expression in insect cells, one-step purification and characterization of a recombinant phospholipase D from cowpea (Vigna unguiculata L. Walp)

Phospholipase D (PLD) is an important enzyme involved in signaltransduction, vesicle trafficking and membrane metabolism. Inthis study, large amounts of a recombinant plant PLD were secretedinto the culture medium of baculovirus-infected insect cellsand purified to homogeneity in the form of a fully active enzyme.The transient production of recombinant PLD yielded a protein(rPLDa, 88 kDa) together with a shorter form (rPLDb, 87 kDa),which accumulated in the medium. N-Terminal amino acid sequencingof the rPLDa and rPLDb showed that rPLDb resulted from proteolyticcleavage at Gly8–Ile9. Immunoblotting showed that bothrPLDa and rPLDb are recognized by a polyclonal antibody previouslyraised against native soybean PLD. One-step calcium-dependentoctyl-Sepharose chromatography was used to obtain the two highlypurified forms of rPLD, as attested by gel electrophoresis,N-terminal amino acid sequence and mass spectrometry. The N-terminalregion of PLD is homologous with the C2 domains which are presentin a number of enzymes known to be involved in signal transductionand/or phospholipid metabolism. The truncated rPLDb lacks thefirst acidic amino acid in its N-terminus, which is probablyinvolved in the calcium binding site. The rPLDb was thus easilyeluted from the octyl-Sepharose column by decreasing the calciumconcentration of the buffer from 50 to 30 mM, whereas, the rPLDawas eluted after chelating calcium ions with EDTA. The purifiedrPLD yield reached a level of 10 mg per liter of serum-freeculture medium. The availability of baculovirus-derived rPLDconstitutes a valuable source of enzyme for future crystallographicstudies to determine its three-dimensional structure.     

Detecting deception attacks in cyber-physical linear parameter varying systems with packet loss

The increased connectivity of cyber-physical systems (CPS) to enterprise networks raises challenging security concerns. Detecting attacks on CPS is a vital step to improving their security. Most of the existing attack detectors are for CPS with linear dynamics. In this study, an investigation is made for designing a detector of deception attacks in a cyber-physical linear parameter varying (LPV) system in the presence of packet loss. A model-based attack detector is designed to detect deception attacks on output measurements, actuators, or schedule variables. With an unreliable network, the LPV attack detector enhances detection capacity and attenuates disturbances on the detector module to improve detection accuracy. During communication, packet loss results in network unreliability, which is modeled by the Bernoulli process. Stochastic stability is used to determine LPV attack detector parameters. A residual signal is built by comparing the detector's output and the actual sensor measurement and provides the deception attack's essential data. However, the packet loss causes some impulse signals in the residual signal, resulting in false alarms. Therefore, the detector module is equipped with a median filter to suppress packet loss's effect on evaluating the residual signal. Tests and validations of the proposed approach are performed on a two-tank system and a continuous stirred tank reactor. According to evaluation results conducted on two testbeds, the proposed method accurately detects deception attacks even when there is packet loss.