162 research outputs found
Novel calixarene-based porous organic polymers with superfast removal rate and ultrahigh adsorption capacity for selective separation of cationic dyes
No full textExploring novel porous adsorbents for efficient water purification is a significant and urgent task. Two novel calixarene-based porous organic polymers (POPs) namely POP-8F and POP-10F were synthesized via a simple and mild reaction using octafluoronaphthalene and decafluorobiphenyl as the crosslinker. The Fourier transform infrared spectrometer, solid-state 13C NMR spectra prove the successful construction of the POPs, and thermal gravimetric analyzer curves demonstrate the good thermal stabilities. Combining the advantages of porous structures, abundant adsorption sites and electronegative natures, both POP-8F and POP-10F exhibit extraordinary adsorption capacities and rates towards cationic dyes including Rhodamine B (RhB), methylene blue (MB) and crystal violet (CV). Especially for RhB, the removal efficiency can reach nearly 99 % within 4 min and the pseudo-second-order rate constant of POP-8F is 0.04386 g mg−1 min−1. Notably, the maximum adsorption capacity of POP-8F towards RhB is 2433 mg g−1, surpassing all the previously reported porous adsorbents including covalent organic frameworks, metal organic frameworks, POPs, biomass adsorbents, activated carbons, etc. In addition, both POP-8F and POP-10F can selectively adsorb cationic dyes among the mixtures of cationic dyes and anionic dyes. More importantly, the calixarene-based POPs can efficiently remove cationic dyes through a simple column filtration and exhibit excellent reusability properties. All the above characteristics make POP-8F and POP-10F excellent porous adsorbents for water pollutant treatment and purificatio
Robot-Assisted Underwater Acoustic Imaging For Bridge Scour Evaluation
No full textScour is responsible for more than half of the bridges that collapsed in the U.S. over the past four decades. In recent years, the smart rock technology has been developed and validated in field conditions to estimate the maximum depth of a scour hole that has ever been formed around a bridge pier. With a cylindrical magnet (N42), the most sensitive and reliable measurement distance for each smart rock ranges from 1.5 m to 7.5 m. This measurement distance is insufficient in flood seasons when water level reaches to a high elevation. This project aims to develop an underwater acoustic imaging and water depth measuring system with a side-scan sonar and a digital precision altimeter.
A dual-chamber climbing robot that can carry a side-scan sonar or a digital precision altimeter will be prototyped and tested for maneuverability, stability, and functionality under various operation conditions in air or underwater. The technical specifications of an integrated system of the robot and sonar/altimeter will be developed based on laboratory tests. The field performance of the system at a bridge site will be documented in terms of the sensitivity and variability of the side-scan sonar and the digital precision altimeter in scour depth measurement, and stability and maneuverability of the climbing robot
Enhanced magnetoelectric effect in ferromagnetic-elastic-piezoelectric composites
No full textThe non-magnetostrictive magnetoelectric (ME) effect was realized in a simple ferromagnetic-elastic-piezoelectric (FEP) composite. The FEP composite comprised two piezoceramic Pb(Zr,Ti)O-3 (PZT) plates and NdFeB magnets elastically coupled by a cantilever beam made of phosphor copper-sheet. The effects of the beam length on the ME coefficient and the linear relationship between the ME voltage output and the applied magnetic field at the resonant frequency were experimentally investigated. A notably superior ME coefficient of 3800 V/cm Oe at extremely low resonant frequency of 5.524 Hz was obtained for the FEP composite with the phosphor copper-sheet beam length of 8 cm. Such a composite structure shows the possibility to obtain a magnetic sensor element with ultrahigh sensitivity in low frequency range. The results are of great importance for the basic understanding of the new way to realize giant ME effect and the optimal design of such a composite structure with high ME coefficient. (C) 2014 Elsevier B.V. All rights reserved.Chemistry, PhysicalMaterials Science, MultidisciplinaryMetallurgy & Metallurgical EngineeringSCI(E)[email protected]; [email protected]
Control Performance Simulation on Heave Compensation System of Deep-sea Mining Based on Dynamic Vibration Absorber
No full textModeling and simulation of active-controlled heave compensation system of deep-sea mining based on dynamic vibration absorber
No full textModeling of active heave compensation system of deep-sea mining based on dynamic vibration absorber and its H<inf>&#x221E;</inf> robust control
No full textDistributed inference for the extreme value index
No full textIn this paper we investigate a divide-And-conquer algorithm for estimating the extreme value index when data are stored in multiple machines. The oracle property of such an algorithm based on extreme value methods is not guaranteed by the general theory of distributed inference. We propose a distributed Hill estimator and establish its asymptotic theories. We consider various cases where the number of observations involved in each machine can be either homogeneous or heterogeneous, and either fixed or varying according to the total sample size. In each case we provide a sufficient, sometimes also necessary, condition under which the oracle property holds
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