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Showing papers by "University of Science and Technology Beijing published in 2012"


Journal ArticleDOI
TL;DR: Five practical examples involving a wide variety of systems and analysis methods are given to illustrate the usefulness of Multiwfn, a multifunctional program for wavefunction analysis.
Abstract: Multiwfn is a multifunctional program for wavefunction analysis. Its main functions are: (1) Calculating and visualizing real space function, such as electrostatic potential and electron localization function at point, in a line, in a plane or in a spatial scope. (2) Population analysis. (3) Bond order analysis. (4) Orbital composition analysis. (5) Plot density-of-states and spectrum. (6) Topology analysis for electron density. Some other useful utilities involved in quantum chemistry studies are also provided. The built-in graph module enables the results of wavefunction analysis to be plotted directly or exported to high-quality graphic file. The program interface is very user-friendly and suitable for both research and teaching purpose. The code of Multiwfn is substantially optimized and parallelized. Its efficiency is demonstrated to be significantly higher than related programs with the same functions. Five practical examples involving a wide variety of systems and analysis methods are given to illustrate the usefulness of Multiwfn. The program is free of charge and open-source. Its precompiled file and source codes are available from http://multiwfn.codeplex.com.

17,273 citations


Journal ArticleDOI
TL;DR: In this article, the phase formation for multi-component alloys has been predicted by calculating parameters Ω and δ for typical multichamber alloys reported, where Ω is defined as a parameter of the entropy of mixing timing the average melting temperature of the elements over the enthalpy of mixing, δ is the mean square deviation of the atomic size of elements.

1,559 citations


Journal ArticleDOI
TL;DR: In this paper, the authors focus on the important role and challenges of high-k polymer-matrix composites (PMC) in new technologies and discuss potential applications of highk PMC.

1,412 citations


Journal ArticleDOI
TL;DR: This article proposes a simple and reliable method to eliminate these unreasonably distributed surface vertices generated in the original MT, which can save more than 60% of total analysis time of electrostatic potential, yet the loss in accuracy is almost negligible.
Abstract: Quantitative analysis of molecular surface is a valuable technique for analyzing non-covalent interaction, studying molecular recognition mode, predicting reactive site and reactivity. An efficient way to realize the analysis was first proposed by Bulat et al. (J. Mol. Model., 16, 1679), in which Marching Tetrahedra (MT) approach commonly used in computer graphics is employed to generate vertices on molecular surface. However, it has been found that the computations of the electrostatic potential in the MT vertices are very expensive and some artificial surface extremes will be presented due to the uneven distribution of MT vertices. In this article, we propose a simple and reliable method to eliminate these unreasonably distributed surface vertices generated in the original MT. This treatment can save more than 60% of total analysis time of electrostatic potential, yet the loss in accuracy is almost negligible. The artificial surface extremes are also largely avoided as a byproduct of this algorithm. In addition, the bisection iteration procedure has been exploited to improve accuracy of linear interpolation in MT. The most appropriate grid spacing for surface analysis has also been investigated. 0.25 and 0.20 bohr are recommended to be used for surface analysis of electrostatic potential and average local ionization energy, respectively.

1,205 citations


Journal ArticleDOI
10 Jul 2012-JOM
TL;DR: In this paper, the phase diagram of high-entropy alloys was used to predict the phase formation of HEAs, namely Ω ≥ 1.1 and δ ≤ 6.6%.
Abstract: This article reviews the recent work on the high-entropy alloys (HEAs) in our group and others. HEAs usually contain five or more elements, and thus, the phase diagram of HEAs is often not available to be used to design the alloys. We have proposed that the parameters of δ and Ω can be used to predict the phase formation of HEAs, namely Ω ≥ 1.1 and δ ≤ 6.6%, which are required to form solid-solution phases. To test this criterion, alloys of TiZrNbMoVx and CoCrFeNiAlNbx were prepared. Their microstructures mainly consist of simple body-centered cubic solid solutions at low Nb contents. TiZrNbMoVx alloys possess excellent mechanical properties. Bridgman solidification was also used to control the microstructure of the CoCrFeNiAl alloy, and its plasticity was improved to be about 30%. To our surprise, the CoCrFeNiAl HEAs exhibit no apparent ductile-to-brittle transition even when the temperatures are lowered from 298 K to 77 K.

532 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examine a manufacturer's pricing strategies in a dual-channel supply chain, in which the manufacturer is a Stackelberg leader and the retailer is a follower.
Abstract: We examine a manufacturer's pricing strategies in a dual-channel supply chain, in which the manufacturer is a Stackelberg leader and the retailer is a follower. We show the conditions under which the manufacturer and the retailer both prefer a dual-channel supply chain. We examine the coordination schemes for a dual-channel supply chain and find that a manufacturer's contract with a wholesale price and a price for the direct channel can coordinate the dual-channel supply channel, benefiting the retailer but not the manufacturer. We illustrate how such a contract with a complementary agreement, such as a two-part tariff or a profit-sharing agreement, can coordinate the dual-channel supply chain and enable both the manufacturer and the retailer to be a win–win.

436 citations


Journal ArticleDOI
TL;DR: A non-linear model to estimate the remaining useful life of a system based on monitored degradation signals is presented and it is revealed that considering nonlinearity in the degradation process can significantly improve the accuracy of remaining usefulLife estimation.
Abstract: Remaining useful life estimation is central to the prognostics and health management of systems, particularly for safety-critical systems, and systems that are very expensive. We present a non-linear model to estimate the remaining useful life of a system based on monitored degradation signals. A diffusion process with a nonlinear drift coefficient with a constant threshold was transformed to a linear model with a variable threshold to characterize the dynamics and nonlinearity of the degradation process. This new diffusion process contrasts sharply with existing models that use a linear drift, and also with models that use a linear drift based on transformed data that were originally nonlinear. Both existing models are based on a constant threshold. To estimate the remaining useful life, an analytical approximation to the distribution of the first hitting time of the diffusion process crossing a threshold level is obtained in a closed form by a time-space transformation under a mild assumption. The unknown parameters in the established model are estimated using the maximum likelihood estimation approach, and goodness of fit measures are applied. The usefulness of the proposed model is demonstrated by several real-world examples. The results reveal that considering nonlinearity in the degradation process can significantly improve the accuracy of remaining useful life estimation.

423 citations


Journal ArticleDOI
TL;DR: Investigation of the presence and distribution of antibiotics in the water, sediments, and biota samples from Baiyangdian Lake, China revealed that antibiotics were widely distributed and Salvinia natans exhibited the highest bioaccumulation capability for quinolones among three species of aquatic plants.

411 citations


Journal ArticleDOI
TL;DR: In this paper, the spectral structure of planetary gear system vibration signals is used to diagnose planetary gearboxes with respect to the frequency of local and distributed gear faults. And the theoretical derivations are validated using both experimental and industrial signals.

402 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructures and properties of the AlCoCrFeNbxNi high-entropy alloys (HEAs) were investigated and two phases were found: body-centered-cubic (BCC) solid solution phase and the Laves phase of (CoCr)Nb type.
Abstract: The microstructures and properties of the AlCoCrFeNbxNi high-entropy alloys (HEAs) were investigated. Two phases were found in the prepared AlCoCrFeNbxNi HEAs: one is body-centered-cubic (BCC) solid solution phase; the other is the Laves phase of (CoCr)Nb type. The microstructures of the alloy series vary from hypoeutectic to hypereutectic, and the compressive yield strength and Vickers hardness have an approximately linear increase with increasing Nb content. The residual magnetization (Mr) reaches a maximum for AlCoCrFeNb0.1Ni alloy, which is 6.106 emu/g. The factor of Ω, which is defined as entropy of mixing times 1000 over enthalpy of mixing, well predicts the phase formation for the multicomponents alloys.

381 citations


Journal ArticleDOI
TL;DR: In this paper, the preservation of the molecular dipole moment is imposed upon the Hirshfeld population analysis as another constraint to improve the original Hirschfeld charges, where each atomic dipolar moment defined by the deformation density is expanded as contributions from all atoms in the molecule.
Abstract: Charge preservation is a necessary condition in population analysis. However, one such constraint is not enough to solve the arbitrariness involved in the population analysis such as Hirshfeld population. This arbitrariness results in too small Hirshfeld charges and poor reproducibility of molecular dipolar moments. In this article, the preservation of the molecular dipole moment is imposed upon the Hirshfeld population analysis as another constraint to improve the original Hirshfeld charges. In the scheme each atomic dipolar moment defined by the deformation density is expanded as contributions from all atoms in the molecule. The corresponding correction charges are then accumulated for each atom together with the original Hirshfeld charge as the predicted charge. All computed charges are generally larger than Hirshfeld charges, independent of basis set, and have very good electrostatic potential reproducibility and high correlation with the charges derived from the electrostatic potential fitting.

Journal ArticleDOI
TL;DR: The phase change behaviors of polyethylene glycol (PEG)/porous carbon composites are extensively studied in this article, where three types of shape-stabilized PCMs were prepared using expanded graphite (EG), active carbon (AC) and ordered mesoporous carbon (CMK-5) as supporting materials with various pore structures.

Journal ArticleDOI
TL;DR: The occurrence, removal efficiency and seasonal variation of 22 antibiotics, including eight fluoroquinolones, nine sulfonamides and five macrolides, were investigated in eight sewage treatment plants (STPs) in Beijing, China, with ofloxacin having the highest concentration in all the sludge samples.

Journal ArticleDOI
01 Aug 2012
TL;DR: The OpenWSN project is an open‐source implementation of a fully standards‐based protocol stack for capillary networks, rooted in the new IEEE802.15.4e Time Synchronized Channel Hopping standard, which enables ultra‐low‐power and highly reliable mesh networks, which are fully integrated into the Internet.
Abstract: The OpenWSN project is an open-source implementation of a fully standards-based protocol stack for capillary networks, rooted in the new IEEE802.15.4e Time Synchronized Channel Hopping standard. IEEE802.15.4e, coupled with Internet of Things standards, such as 6LoWPAN, RPL and CoAP, enables ultra-low-power and highly reliable mesh networks, which are fully integrated into the Internet. The resulting protocol stack will be cornerstone to the upcoming machine-to-machine revolution. This article gives an overview of the protocol stack, as well as key integration details and the platforms and tools developed around it. The pure-C OpenWSN stack was ported to four off-the-shelf platforms representative of hardware currently used, from older 16-bit microcontroller to state-of-the-art 32-bit Cortex-M architectures. The tools developed around the low-power mesh networks include visualisation and debugging software, a simulator to mimic OpenWSN networks on a PC, and the environment needed to connect those networks to the Internet. Experimental results presented in this article include a network where motes operate at an average radio duty cycle well below 0.1% and an average current draw of 68 μA on off-the-shelf hardware. These ultra-low-power requirements enable a range of applications, with motes perpetually powered by micro-scavenging devices. OpenWSN is, to the best of our knowledge, the first open-source implementation of the IEEE802.15.4e standard. Copyright © 2012 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the electrochemical behavior of duplex stainless steel in alkaline solutions with different pH values in the presence of NaCl was evaluated by different techniques: potentiodynamic measurements, electrochemical impedance spectroscopy and capacitance measurements (Mott-Schottky approach).

Journal ArticleDOI
23 Jan 2012-Small
TL;DR: Titania nanoparticles (P25) are successfully chemically bonded with graphdiyne (GD) nanosheets by a facile hydrothermal treatment, to form a novel nanocomposite photocatalyst that exhibits higher photocatalytic activity for degrading methylene blue under UV irradiation and might find potential application in a wide range of fields including air purification and waste water treatment.
Abstract: Titania nanoparticles (P25) are successfully chemically bonded with graphdiyne (GD) nanosheets by a facile hydrothermal treatment, to form a novel nanocomposite photocatalyst. The as-prepared P25-GD nanocomposite exhibits higher photocatalytic activity for degrading methylene blue under UV irradiation than not only P25 and P25-carbon nanotube composite but also the current well-known P25-graphene composite photocatalysts. Moreover, P25-GD also shows considerable visible-light-driven photocatalytic activity, since the formation of chemical bonds between P25 and GD effectively decreases the bandgap of P25 and extends its absorbable light range. The photocatalytic activity of P25-GD can be adjusted by changing the content of GD in composites and the optimized value is about 0.6 wt%. Such a nanocomposite photocatalyst might find potential application in a wide range of fields including air purification and waste water treatment.

Journal ArticleDOI
TL;DR: Higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz, which provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectrics materials.
Abstract: In this work, two series of nanocomposites of poly(vinylidene fluoride) (PVDF) incorporated with reduced graphene oxide (rGO) and poly(vinyl alcohol)-modified rGO (rGO-PVA) were fabricated using solution-cast method and their dielectric properties were carefully characterized. Infrared spectroscopy and atom force microscope analysis indicated that PVA chains were successfully grafted onto graphene through ester linkage. The PVA functionalization of graphene surface can not only prevent the agglomeration of original rGO but also enhance the interaction between PVDF and rGO-PVA. Strong hydrogen bonds and charge transfer effect between rGO-PVA and PVDF were determined by infrared and Raman spectroscopies. The dielectric properties of rGO-PVA/PVDF and rGO/PVDF nanocomposites were investigated in a frequency range from 10² Hz to 10⁷ Hz. Both composite systems exhibited an insulator-to-conductor percolating transition as the increase of the filler content. The percolation thresholds were estimated to be 2.24 vol % for rGO-PVA/PVDF composites and 0.61 vol % for rGO/PVDF composites, respectively. Near the percolation threshold, the dielectric permittivity of the nanocomposites was significantly promoted, which can be well explained by interfacial polarization effect and microcapacitor model. Compared to rGO/PVDF composites, higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz. This work provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectric materials.

Journal ArticleDOI
TL;DR: Considering the spectral complexity of planetary gearbox vibration signals as well as their amplitude modulation and frequency modulation (AMFM) nature, a simple yet effective method was proposed in this paper based on amplitude and frequency demodulations.

Journal ArticleDOI
TL;DR: The large planar surface of GO allows simultaneous quenching of several DNA probes with different dyes and produces a multiple biosensing platform with high sensitivity and selectivity, which has promising application in profiling the pattern of miRNA expression and biomedical research.
Abstract: A simple, highly sensitive, and selective multiple microRNA (miRNA) detection method based on the graphene oxide (GO) fluorescence quenching and isothermal strand-displacement polymerase reaction (ISDPR) was proposed. The capability to discriminate ssDNA and double-stranded nucleic acid structure coupled with the extraordinary fluorescence quenching of GO on multiple organic dye allows the proposed strategy to simultaneously and selectively detect several miRNA labeled with different dyes in the same solution, while the ISDPR amplification endows the detection method with high sensitivity. The strong interaction between ssDNA and GO led to the fluorescent ssDNA probe exhibiting minimal background fluorescence. Upon the recognition of specific target miRNA, an ISDPR was triggered to produce numerous massive specific DNA-miRNA duplex helixes, and a strong emission was observed due to the weak interaction between the DNA-miRNA duplex helix and GO. A miRNA biosensor down to 2.1 fM with a linear range of 4 ord...

Journal ArticleDOI
TL;DR: In this article, high phase-purity BiCuSeO polycrystalline materials with fine grains were synthesized by a facile method combining a solid-state reaction and spark plasma sintering.
Abstract: This work revealed that BiCuSeO oxyselenide is a potential oxide-based thermoelectric material, whose dimensionless figure of merit (ZT) reaches ∼0.70 at 773 K. High phase-purity BiCuSeO polycrystalline materials with fine grains were synthesized by a facile method combining a solid-state reaction and spark plasma sintering. Purifying the constitutive phase and reducing the grain sizes by introducing a high-energy ball milling process before spark plasma sintering were found to be effective in property enhancement. The resultant single-phased BiCuSeO sample derived from ball-milled powders shows good electrical conductivity above 4.0 × 103 S m−1 and a large Seebeck coefficient above 200 μV K−1. This compound has a low thermal conductivity (∼0.5 W m−1 K−1), which is associated with its low phonon transport speed and Young's modulus. Results indicated that BiCuSeO-based materials are promising for energy conversion applications in the moderate temperature range.

Journal ArticleDOI
TL;DR: In this article, the authors used a series of thermo-mechanical treatments to study the stability of the solid solution phases in a high-entropy Al0.5CoCrCuFeNi alloy.

Journal ArticleDOI
TL;DR: The research progress on piezotronic properties of ZnO nanomaterials investigated by scanning probe microscopy (SPM) and ZNO-based prototype pieZotronic nanodevices built in virtue of SPM are introduced.
Abstract: ZnO nanomaterials with their unique semiconducting and piezoelectric coupled properties have become promising materials for applications in piezotronic devices including nanogenerators, piezoelectric field effect transistors, and diodes. This article will mainly introduce the research progress on piezotronic properties of ZnO nanomaterials investigated by scanning probe microscopy (SPM) and ZnO-based prototype piezotronic nanodevices built in virtue of SPM, including piezoelectric field effect transistors, piezoelectric diodes, and strain sensors. Additionally, nanodamage and nanofailure of ZnO materials and their relevant piezotronic nanodevices will be critically discussed in their safe service in future nanoelectromechanical system (NEMS) engineering.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the electrical and thermal transport properties of lead-based chalcogenides (PbTe, PbSe, and PbS) with special emphasis on the lattice and the bipolar thermal conductivity.

Journal ArticleDOI
TL;DR: In this paper, uniform and spherical LiNi 0.5 Co 0.2 Mn 0.3 O 2 particles were successfully coated with AlF 3, and the structures and electrochemical properties of AlF3 -coated LiNi0.5 CO 0.1 O 2 were characterized by various techniques.

Journal ArticleDOI
TL;DR: The results show that thermal pretreatment at 175 °C/60 min significantly decreases viscosity, improves the MBW dewatering performance, as well as increases soluble chemical oxygen demand, soluble sugar, soluble protein, and especially organic compounds with molecular weights >10 kDa.

Journal ArticleDOI
TL;DR: In this article, refractory high entropy alloys with the compositions of NbTiVTaAlx were prepared under a high-purity argon atmosphere and their microstructure and compressive properties at room temperature were investigated.

Journal ArticleDOI
TL;DR: This paper reviews the recent advances in delay-time-based maintenance modelling, which is one of the mathematical techniques for optimising inspection planning and related problems.

Journal ArticleDOI
TL;DR: The occurrence, distribution and bioaccumulation of 22 antibiotics, including eight fluoroquinolones (FQs), nine sulfonamides (SAs) and five macrolides (MLs), in the Haihe River were investigated and sediments are an important reservoir for FQs as they are strongly adsorbed onto sediments.
Abstract: The occurrence, distribution and bioaccumulation of 22 antibiotics, including eight fluoroquinolones (FQs), nine sulfonamides (SAs) and five macrolides (MLs), in the Haihe River were investigated. Surface water, sediment and fish samples were analyzed by HPLC-MS/MS. Ofloxacin, sulfamethoxazole, sulfadiazine, erythromycin and roxithromycin were found in all surface water samples. SAs were the predominant antibiotics in surface water samples in the mainstream of Haihe River, with the maximum concentration of 201 ng L−1 for sulfamethoxazole. Compared with Haihe River, higher concentrations of antibiotics were found in the surface water samples in the Dagu and Chentaizi Drainage Rivers. The antibiotics pollution in the mainstream of Haihe River may derive from its tributaries, whereas the wastewater from fish ponds was not the main source of FQs, SAs and MLs in the river water. In sediment samples, FQs were the most frequently detected antibiotics and their concentrations were much higher than SAs and MLs. The high concentrations and detection frequencies of FQs in sediments indicate that sediments are an important reservoir for FQs as they are strongly adsorbed onto sediments. Ciprofloxacin and erythromycin exhibited potential bioaccumulation in crucian carp, with mean bioaccumulation factors of 3262 L kg−1 and 4492 L kg−1, respectively.

Journal ArticleDOI
TL;DR: Because of the high heat storage capacity and the moderate phase change temperature, the PEG-GO composite is a promising heat energy storage candidate at mild temperature.
Abstract: Graphene oxide (GO) sheets were introduced to stabilize the melted polyethylene glycol (PEG) during the solid–liquid phase change process, which can be used as a smart heat storage system. The structural properties and phase change behaviors of the PEG–GO composites were comprehensively investigated as a function of the PEG content by means of various characterization techniques. The highest stabilized PEG content is 90 wt% in the composites, resulting in a heat storage capacity of 156.9 J g−1, 93.9% of the phase change enthalpy of pure PEG. Notably, GO has much stronger impact on lowering of the phase change temperature of PEG compared with some other porous carbon materials (activated carbon and ordered mesoporous carbon) due to the unique thin layer structure of GO. Because of the high heat storage capacity and the moderate phase change temperature, the PEG–GO composite is a promising heat energy storage candidate at mild temperature.

Journal ArticleDOI
10 Jul 2012-ACS Nano
TL;DR: A thermoelectric nanogenerator made from a single Sb-doped ZnO micro/nanobelt that generates an output power of about 1.94 nW under a temperature difference of 30 K between the two electrodes is demonstrated.
Abstract: We demonstrate a thermoelectric nanogenerator (NG) made from a single Sb-doped ZnO micro/nanobelt that generates an output power of about 1.94 nW under a temperature difference of 30 K between the two electrodes. A single Sb-doped ZnO microbelt was bonded at its ends on a glass substrate as a NG, which can give an output voltage of 10 mV and an output current of 194 nA. The single Sb-doped ZnO microbelt shows a Seebeck coefficient of about −350 μV/K and a high power factor of about 3.2 × 10–4 W/mK2. The fabricated NG demonstrated its potential to work as a self-powered temperature sensor with a reset time of about 9 s.