Showing papers by "University of Science and Technology Beijing published in 2011"
TL;DR: This paper systematically reviews the recent modeling developments for estimating the RUL and focuses on statistical data driven approaches which rely only on available past observed data and statistical models.
1,667 citations
TL;DR: An overview of advances in the synthesis of YSNs with controllable sizes, compositions, geometries, structures and functionalities is provided, covering systematic synthesis approaches and key promising applications.
768 citations
17 Sep 2011
TL;DR: Failed urban planning is detected using the GPS trajectories of taxicabs traveling in urban areas using the trajectories generated by 30,000 taxis from March to May in 2009 and 2010 in Beijing, and the results can evaluate the effectiveness of the carried out planning.
Abstract: Urban computing for city planning is one of the most significant applications in Ubiquitous computing. In this paper we detect flawed urban planning using the GPS trajectories of taxicabs traveling in urban areas. The detected results consist of 1) pairs of regions with salient traffic problems and 2) the linking structure as well as correlation among them. These results can evaluate the effectiveness of the carried out planning, such as a newly built road and subway lines in a city, and remind city planners of a problem that has not been recognized when they conceive future plans. We conduct our method using the trajectories generated by 30,000 taxis from March to May in 2009 and 2010 in Beijing, and evaluate our results with the real urban planning of Beijing.
518 citations
TL;DR: It is suggested that the strong interaction between h-BT fillers and PVDF matrix is the main reason for the improved dielectric properties of the h- BT/PVDF composites.
Abstract: Dielectric properties of poly(vinylidene fluoride) (PVDF) based nanocomposites filled with surface hydroxylated BaTiO(3) (h-BT) nanoparticles were reported. The h-BT fillers were prepared from crude BaTiO(3) (c-BT) in aqueous solution of H(2)O(2). Results showed that the dielectric properties of the h-BT/PVDF nanocomposites had weaker temperature and frequency dependences than that of c-BT/PVDF nanocomposites. Meanwhile, the h-BT/PVDF composites showed lower loss tangent and higher dielectric strength. It is suggested that the strong interaction between h-BT fillers and PVDF matrix is the main reason for the improved dielectric properties.
372 citations
TL;DR: In this paper, the authors presented a theoretical and experimental study on thermal conductivities of silica aerogel, xonotlite-type calcium silicate, and xonotonite-aerogel composite insulation material.
353 citations
TL;DR: In this paper, a robust and simple procedure to prepare polymer-based composites with a remarkable molecular level interaction at interfaces through melt-mixing pristine multiwalled carbon nanotubes (MWNTs) within polyvinylidene fluoride (PVDF) matrix is presented.
Abstract: Carbon nanotubes have unprecedented electronic properties and large specific areas as nanoscale fillers, but their potential has not been fully realized in polymer composites due to the poor dispersion and weak interfacial interaction. Here, we present a robust and simple procedure to prepare polymer-based composites with a remarkable molecular level interaction at interfaces through melt-mixing pristine multiwalled carbon nanotubes (MWNTs) within poly(vinylidene fluoride) (PVDF) matrix. The interfacial interaction is confirmed by Raman spectroscopy as well as the formation of much thin PVDF layer on individual MWNT. The resultant nanocomposite with a huge interfacial area possesses a giant dielectric permittivity (3800) of 3 orders of magnitude higher than the PVDF matrix, while retaining a low conductivity level (6.3 × 10−5 S.m−1) and an excellent thermal stability. These results could be explained by a reinforced Maxwell−Wagner−Sillars (MWS) effect based on the remarkable molecular level interaction.
335 citations
TL;DR: In this article, a hierarchical porous carbon structure was characterized by nitrogen sorption at 77 K, scanning electron microscopy and X-ray diffraction, and the specific capacitance was 185 F/g at a current density of 0.05 A/g.
334 citations
TL;DR: In this paper, the authors developed a new method for the preparation of high value, environmentally friendly products from tailings Magnetic Fe3O4 nano-powder was synthesized by ultrasonic assisted chemical co-precipitation utilizing high purity iron separated from iron ore tailings by acidic leaching method Magnetite particles with 15nm average diameter were characterized by X-ray diffraction, field-emission scanning electron microscopy and vibrating sample magnetometer.
330 citations
TL;DR: In this article, a hierarchical porous carbon/sulfur composites with a unique hierarchical porous structure was prepared by KOH activation and the effects of activation temperature on the textural properties of the pig bone-based carbons were investigated.
Abstract: Pig bone derived carbon with a unique hierarchical porous structure was prepared by potassium hydroxide (KOH) activation. The effects of activation temperature on the textural properties of the pig bone based carbons were investigated. The hierarchical porous carbons exhibit the largest BET specific surface areas and pore volume when the activation temperature reaches 850 °C, and the carbon still maintains a highly hierarchical structure even when the temperature is up to 950 °C. The pig bone derived hierarchical porous carbon/sulfur composites have been tested as a novel cathode for lithium–sulfur batteries. The result shows that the cycle stability and the utilization of sulfur in the lithium–sulfur batteries have been largely improved. The hierarchical porous carbon/sulfur cathode has a high initial capacity of 1265 mAh g−1 and 643 mAh g−1 after 50 cycles, which is higher than that of the normal cathodes with compact structures.
308 citations
300 citations
TL;DR: In this paper, the dependence of microstructure on the alloy composition and cooling rate of a series of (Zr0.5Cu 0.5)100−xAlx was investigated in detail and explained in the framework of time-temperature-transformation diagrams.
TL;DR: The electrical conductivity and Seebeck coefficient of BiCu(1-x)SeO indicate that the carriers were introduced in the (Cu(2)Se(2))(2)- layer by Cu deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.
Abstract: A significant enhancement of thermoelectric performance in layered oxyselenides BiCuSeO was achieved. The electrical conductivity and Seebeck coefficient of BiCu(1-x)SeO (x = 0-0.1) indicate that the carriers were introduced in the (Cu(2)Se(2))(2-) layer by Cu deficiencies. The maximum of electrical conductivity is 3 × 10(3) S m(-1) for Bicu(0.975)Seo at 650 °C, much larger than 470 S m(-1) for pristine BiCuSeO. Featured with very low thermal conductivity (∼0.5 W m(-1) K(-1)) and a large Seebeck coefficient (+273 μV K(-1)), ZT at 650 °C is significantly increased from 0.50 for pristine BiCuSeO to 0.81 for BiCu(0.975)SeO by introducing Cu deficiencies, which makes it a promising candidate for medium temperature thermoelectric applications.
TL;DR: In this paper, a dual-phase bulk metallic glass matrix composite (BMGMC) with a homogeneous distribution of dendrites and the composition of Ti 46 Zr 20 V 12 Cu 5 Be 17 is characterized by a high tensile strength of ∼1640 MPa and a large tensile strain of ∼15.5% at room temperature.
TL;DR: In this paper, the electrocaloric effect (ECE) of lead-free ferroelectric ceramics was characterized via P-T curves under different electric fields, which indicated that the NBT has an abnormal ECE with a negative temperature change (ΔT140 −−0.33 −kV/cm) opposite to that of the normal ferroelectrics.
TL;DR: In this article, the problems involved in the fabrication and the brazing of these composites were elucidated and the main focus was put on the discussion of the methods to overcome these difficulties.
TL;DR: In this paper, the isothermal oxidation behavior of Ti-45Al-8Nb and Ti-52Al- 8Nb alloys at 900°C in air was investigated.
TL;DR: In this paper, a nano-sized SiO x /C composite with core-shell structure is prepared by a modified Stober method, which shows high specific capacity (ca. 800 mAh −1 ), excellent cycling stability, good rate-capability but low initial coulombic efficiency.
TL;DR: The polycrystalline Cu(1.8)S compounds were fabricated by using a combined process of mechanical alloying and spark plasma sintering and shows its maximum ZT value 0.5 at 673 K which is the highest value for p-type sulfide thermoelectric materials so far.
TL;DR: In this article, a high thermal conductivity of 493 Wm−m−1 K−1 was achieved in the Cu/Ti-coated diamond composites, attributed to the 285nm thick Ti coating.
21 Jun 2011
TL;DR: WSN has the features of high bandwidth and rate, non-line-transmission ability, large-scale data collection and high cost-effective, and the capability of video monitoring, which can not be realized with ZigBee.
Abstract: The Internet of Things(IoT) and Smart Grid are of great importance in promoting and guiding development of information technology and economic. At Present, the application of the IoT develops rapidly, but due to the special requirements of some applications, the existing technology can not meet them very good. Much research work is doing to build IoT. WiFi-based Wireless Sensor Network(WSN) has the features of high bandwidth and rate, non-line-transmission ability, large-scale data collection and high cost-effective, and it has the capability of video monitoring, which can not be realized with ZigBee. The research on WiFi-based WSN and its application has high practical significance to the development of the Internet of Things and Smart Grid. Based on the current research work of applications in the Internet of Things and the characteristics of WiFi-based WSN, this paper discusses the application of WiFi-based WSN in Internet of Things, which includes Smart Grid, Smart Agriculture and Intelligent environment protection.
TL;DR: Anatase TiO(2) nanosheets-based hierarchical spheres with over 90% {001} facets synthesized via a diethylene glycol-solvothermal route were used as photoanodes of dye-sensitized solar cells, which generated an energy conversion efficiency of 7.51%.
TL;DR: In this paper, the microstructures of fusion welding and brazing zones were analyzed in details by transmission electron microscope (TEM) and it was found that fusion welding zone consist of α-Al grains and ternary near-eutectic structure with α -Al, Si and Mg 2 Si Interfacial reaction layers of brazeling joint were composed of α -Ti, nanosize granular Ti 7 Al 5 Si 12 and serration-shaped TiAl 3
TL;DR: An ultrasensitive nucleic acid biosensor based on horseradish peroxidase-gold nanoparticle dual labels and lateral flow strip biosensor (LFSB) that shows great promise for in-field and point-of-care diagnosis of genetic diseases and for the detection of infectious agents.
TL;DR: In this paper, the electrochemical behavior of passive film formed on 2205 duplex stainless steel in 0.1 M Na2S2O3 solutions was investigated using potentiodynamic polarization, EIS, Mott-Schottky analysis and the compositions of oxide film in different passive regions.
TL;DR: It is shown that lateral spin valves with low-resistivity NiFe/MgO/Ag junctions enable efficient spin injection with high applied current density, which leads to the spin-valve voltage increasing 100-fold, suggesting a route to faster and manipulable spin transport for the development of pure spin-current-based memory, logic and sensing devices.
Abstract: The non-local spin injection in lateral spin valves is strongly expected to be an effective method to generate a pure spin current for potential spintronic application. However, the spin-valve voltage, which determines the magnitude of the spin current flowing into an additional ferromagnetic wire, is typically of the order of 1 μV. Here we show that lateral spin valves with low-resistivity NiFe/MgO/Ag junctions enable efficient spin injection with high applied current density, which leads to the spin-valve voltage increasing 100-fold. Hanle effect measurements demonstrate a long-distance collective 2π spin precession along a 6-μm-long Ag wire. These results suggest a route to faster and manipulable spin transport for the development of pure spin-current-based memory, logic and sensing devices.
TL;DR: In this article, continuous measurements of atmospheric ammonia (NH 3 ) were conducted using Ogawa passive samplers from February 2008 to July 2010 at an urban site and from January 2007-July 2010 at a rural site in Beijing, China.
Abstract: . Continuous measurements of atmospheric ammonia (NH 3 ) were conducted using Ogawa passive samplers from February 2008 to July 2010 at an urban site and from January 2007 to July 2010 at a rural site in Beijing, China. NH 4 + in fine particles was also collected at the rural site during 2008–2009. The field comparison between the Ogawa passive samplers and an active analyzer for NH 3 conducted at the urban site assures the quality and accuracy of the measurements. The concentrations of NH 3 at the urban site ranged from 0.7 to 85.1 ppb, with the annual average of 18.5 ± 13.8 and 23.5 ± 18.0 ppb in 2008 and 2009, respectively. The NH 3 concentrations at the rural site were lower than those at urban site, and varied from 0.8 to 42.9 ppb, with the annual average of 4.5 ± 4.6, 6.6 ± 7.0 and 7.1 ± 3.5 ppb in 2007, 2008 and 2009, respectively. The data showed marked seasonal variations at both sites. The results emphasized traffic to be a significant source of NH 3 concentrations in winter in urban areas of Beijing. This was illustrated by the strong correlations of NH 3 with the traffic related pollutants (NO x and CO) and also by the bimodal diurnal cycle of NH 3 concentrations that was synchronized with traffic. Similar patterns were not observed during the summer, suggesting other non-traffic sources became more important. At the rural site, the daily NH 4 + concentrations ranged from 0.10 to 36.53 μg m −3 , with an average of 7.03 μg m −3 from June 2008 to December 2009. Monthly NH 3 were significantly correlated with NH 4 + concentrations. Average monthly NH 3 /NH 4 + ratios varied from 0.13 to 2.28, with an average of 0.73. NH 4 + in PM 2.5 was primarily associated with SO 4 −2 at the rural site.
TL;DR: In this article, a new method is proposed to strengthen interfacial binding between diamond and Cu by coating strong carbide-forming elements, e.g., Ti or Cr on the surface of the diamond through vacuum micro-deposition.
TL;DR: In this paper, a systematic research has been carried out to predict the height of the fractured water conducting zone in the Bulianta coal mine, where two aspects are taken into account: the stratum structure and the vertical distance from the primary key stratum to the coal seam.
TL;DR: Li et al. as discussed by the authors found that permanent migrants tend to stay within the home province and are more likely to have stable jobs and earn high incomes and thus are more adapted to urban lives.
TL;DR: It is demonstrated that annealing treatment of the primary nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure.
Abstract: We present a two-step electrochemical deposition process to synthesize hierarchical zinc oxide (ZnO) nanorod-nanosheet structures on indium tin oxide (ITO) substrate, which involves electrodeposition of ZnO nanosheet arrays on the conductive glass substrate, followed by electrochemical growth of secondary ZnO nanorods on the backbone of the primary ZnO nanosheets. The formation mechanism of the hierarchical nanostructure is discussed. It is demonstrated that annealing treatment of the primary nanosheets synthesized by the first-step deposition process plays a key role in synthesizing the hierarchical nanostructure. Photovoltaic properties of dye-sensitized solar cells (DSSCs) based on hierarchical ZnO nanostructures are investigated. The hierarchical ZnO nanorod-nanosheet DSSC exhibits improved device performance compared to the DSSC constructed using photoelectrode of bare ZnO nanosheet arrays. The improvement can be attributed to the enhanced dye loading, which is caused by the enlargement of internal surface area within the nanostructure photoelectrode. Furthermore, we perform a parametric study to determine the optimum geometric dimensions of the hierarchical ZnO nanorod-nanosheet photoelectrode through adjusting the preparation conditions of the first- and second-step deposition process. By utilizing a hierarchical nanostructure photoelectrode with film thickness of about 7 μm, the DSSC with an open-circuit voltage of 0.74 V and an overall power conversion efficiency of 3.12% is successfully obtained.