bluuebunny/crossref_metadata_2025 huggingface dataset:
Fabrication of monodispersed Au@Ag bimetallic nanorod-loaded nanofibrous membrane with fast thermo-responsiveness and its use as a smart free-standing SERS substrate
Authors: Chen Siyuan , Wang Liying , Dong Xu , Liu Xiaoyun , Zhou Jianfeng , Yang Jianmao , Zha Liusheng
Published: May 2016

Monodispersed core–shell structured Au@Ag bimetallic nanorods-loaded nanofibrous membrane with fast thermo-responsiveness was fabricated by electrospinning and subsequent heat treatment, which can be used as a smart free-standing SERS substrate.
Ether-functionalized ionic liquid based composite membranes for carbon dioxide separation
Authors: Deng Jing , Bai Lu , Zeng Shaojuan , Zhang Xiangping , Nie Yi , Deng Liyuan , Zhang Suojiang
Published: May 2016

The cellulose acetate and ether-functionalized pyridinium-based ionic liquid composite membranes has been designed to improve CO2separation performance.
A novel Li2Mn2.9Ni0.9Co0.2O8spinel composite interweaved with carbon nanotube architecture as a lithium battery cathode
Authors: Pongilat Remith , Nallathamby Kalaiselvi
Published: May 2016

Custom designed Li2Mn2.9Ni0.9Co0.2O8/MWCNT spinel composite, prepared through a template assisted co-precipitation method demonstrates its suitability for lithium battery applications by exhibiting high capacity and high rate capability.
Enduring protection provided by NMITLI118RT+ and its preparation NMITLI118RT+CFM against ischemia/reperfusion injury in rats
Authors: Ahmad Hafsa , Samuel Sheeba Saji , Khandelwal Kiran , Arya Abhishek , Tripathi Shivangi , Agrawal Satish , Sangwan Neelam Singh , Shukla Rakesh , Dwivedi Anil Kumar
Published: May 2016

Withania somnifera Dunal (Ashwagandha), is an Indian medicinal plant with significant pharmacological properties.
Selective adsorption of elastase by surface molecular imprinting materials prepared with novel monomer
Authors: Deng Xiaoming , Chen Chunyan , Xie Jingfan , Cai Changqun , Chen Xiaoming
Published: May 2016

A new functional monomer with diol groups was synthesized and applied to fabricate surface molecular imprinting polymers (SMIPs) microspheres for selective adsorption of elastase.
Stabilization of Eu3+ under a reductive atmosphere by the Al3+ co-doping of Sr2SiO4:Eu2+/Eu3+
Authors: Szczodrowski Karol , Barzowska Justyna , Górecka Natalia , Grinberg Marek
Published: May 2016

The incorporation of aluminum ions into the Sr2SiO4:Eu causes the stabilization of the Eu3+ ions under reductive atmosphere and concentration ratio of europium in both oxidation states ([Eu3+]/[Eu2+]) can be controlled by changing the Al3+ content.
Highly sensitive shape dependent electro-catalysis of TNT molecules using Pd and Pd–Pt alloy based nanostructures
Authors: Soomro Razium Ali , Akyuz Ozlem Polat , Akin Husna , Ozturk Ramazan , Ibupoto Zafar Hussain
Published: May 2016

This study demonstrates the fabrication of a highly sensitive electrochemical sensor designed for the quantification of 2,4,6-trinitrotoluene (TNT).
Polycrystalline iron oxide nanoparticles prepared by C-dot-mediated aggregation and reduction for supercapacitor application
Authors: Chen Dejian , Li Shunxing , Xu Biyan , Zheng Fengying , Zhou Haifeng , Yu Huiwu , Lin Fan , Zhu Xiaoqi
Published: May 2016

A facile strategy to directly prepare three-dimensional, multicomponent, multiphase oxide by solvothermal method and C-dots-mediated aggregation and reduction is demonstrated.
Ratiometric fluorescent pH-sensitive polymers for high-throughput monitoring of extracellular pH
Authors: Zhang Liqiang , Su Fengyu , Kong Xiangxing , Lee Fred , Day Kevin , Gao Weimin , Vecera Mary E. , Sohr Jeremy M. , Buizer Sean , Tian Yanqing , Meldrum Deirdre R.
Published: May 2016

A polymeric water-soluble extracellular pH sensor is developed with fluorescence ratiometric and cell membrane impermeable characters. The pH sensor enables us to exclusively detect the environmental pH of cells in real time.
“Soluble” vs. “insoluble” Prussian blue based catalysts: influence on Fenton-type treatment
Authors: Doumic Lucila I. , Salierno Gabriel , Ramos Cinthia , Haure Patricia M. , Cassanello Miryan C. , Ayude María A.
Published: May 2016

The influence of the synthesis procedure of supported Prussian blue nanoparticles (PBNP) on their activity and stability as a Fenton-type catalyst is studied.
Activity of N,N′-dialkyl-2-trifluoromethylthioimidazolium salts as phase-transfer catalyst for the alkylation of active methylene compounds
Authors: Mizuta Satoshi , Kitamura Kanami , Nishi Kodai , Hashimoto Ryo , Usui Toshiya , Chiba Kenya
Published: May 2016

The design and synthesis of N,N'-dialkyl-2-trifluoromethylthioimidazolium salts as novel catalysts for alkylations of active methylene compounds are described.
Heterogeneous cation induced clusters formed at surfaces of micro-droplets
Authors: Qiu Ran , Sun Jiamu , Zhang Chengsen , Luo Hai
Published: May 2016

A novel group of heterogeneous cations induced clusters (HeteroCICs) formed only at the surface of the micro-droplet is discovered by mass spectrometry (MS).
A highly sensitive glutamic acid biosensor based on the determination of NADH enzymically generated byl-glutamic dehydrogenase
Authors: Lin Xia , Wang Qinghong , Zhu Shu , Xu Juanjuan , Xia Qiao , Fu Yingzi
Published: May 2016

In this article, a sensitive and stereo-selective biosensor forl-glutamic acid (l-Glu) based on the electrochemiluminescence (ECL) of Ru(bpy)32+has been designed by applyingl-glutamic dehydrogenase (GLDH) for enzymatic generation of NADHin situ.
UPLC-QTOF/MS based metabolomics reveals metabolic alterations associated with severe sepsis
Authors: Liang Qun , Liu Han , Xing Haitao , Jiang Yan , Zhang Ai-Hua
Published: May 2016

Severe sepsis (SS) remains among the leading causes of death in both developed and developing countries.
Oxidative esterification of furfural over Au–Pd/HAP-T and Au–Ag/HAP-T bimetallic catalysts supported on mesoporous hydroxyapatite nanorods
Authors: Radhakrishnan Ramakrishnan , Kannan Kathiravan , Kumaravel Sakthivel , Thiripuranthagan Sivakumar
Published: May 2016

Core–shell (Au–Pd) and alloy (Au–Ag) architectured bimetallic mesoporous hydroxyapatite nano rods in the oxidative esterification of furfural.
Synthesis and catalytic application of N-heterocyclic carbene copper complex functionalized conjugated microporous polymer
Authors: Zhou Hui , Zhang Qing-Yong , Lu Xiao-Bing
Published: May 2016

The first example of IPr(CuCl) functionalized conjugated microporous polymer has been synthesized and applied for the hydrosilylation of terminal alkynes and hydrosilylation of CO2. Good catalytic activities and catalytic stability have been achieved.
Simultaneously toughening and strengthening cyanate ester resin with better dielectric properties by building nanostructures in its crosslinked network using polyimide-block-polysiloxane rod-coil block copolymers
Authors: Ye Yayi , Yuan Li , Liang Guozheng , Gu Aijuan
Published: May 2016

The fabrication and origin of high performance cyanate ester resins by building nanostructures in its crosslinked network with polyimide-block-polysiloxane block copolymers.
β-Cyclodextrin as a recyclable catalyst: aqueous phase one-pot four-component synthesis of polyfunctionalized pyrroles
Authors: Konkala Karnakar , Chowrasia Rakhi , Manjari Padma S. , Domingues Nelson L. C. , Katla Ramesh
Published: May 2016

An elegant, mild and straightforward methodology was explored for the first time towards the synthesis of polyfunctionalized pyrroles using β-cyclodextrin as a reusable supramolecular catalyst in aqueous medium.
Freestanding graphene nanosheets and large-area/patterned graphene nanofilms from indium-catalyzed graphite
Authors: Ha Jun Mok , San Lim Hyung , Park Ji Won , Kim Hyun Jin , Cho Sung Oh
Published: May 2016

A simple route to freestanding graphene nanosheets and large-area/patterned graphene nanofilms by thermal annealing of indium and graphite mixture.
A novel nanochannel fabrication for nanofluidic applications using synchrotron radiation via a micro patterned X-ray mask
Authors: Jeon Hyungkook , Kim Jong Hyun , Lim Geunbae
Published: May 2016

Extremely long nano-sized channels were fabricated based on a novel X-ray mask fabrication method. Using the fabricated nanochannels, the generation of ion concentration polarization, a novel transport phenomenon in nanofluidics, was investigated.
Zwitterionic niobium and tantalum complexes with bidentate aminophenol scaffolds: synthesis, structural characterization and use in the ring opening polymerization of lactides
Authors: Roymuhury Sagnik K. , Chakraborty Debashis , Ramkumar Venkatachalam
Published: May 2016

ROP of rac-LA using zwitterionic Nb and Ta complexes resulted in heterotactic enriched PLA.
Effect of chiral 2-ethylhexyl side chains on chiroptical properties of the narrow bandgap conjugated polymers PCPDTBT and PCDTPT
Authors: Fronk Stephanie L. , Wang Ming , Ford Michael , Coughlin Jessica , Mai Cheng-Kang , Bazan Guillermo C.
Published: May 2016

PCPDTBT* and PCDTPT* containing chiral 2-ethylhexyl side chains were synthesized and their resulting chiroptical properties were studied. PCPDTBT* exhibits a stronger chiroptical response compared to PCDTPT*.
Effects of heteroatom substitution in spiro-bifluorene hole transport materials
Authors: Hu Zhao , Fu Weifei , Yan Lijia , Miao Jingsheng , Yu Hongtao , He Yaowu , Goto Osamu , Meng Hong , Chen Hongzheng , Huang Wei
Published: May 2016

By introducing the heteroatom into the benchmark hole transport material Spiro-MeOTAD, the energy level of hole transport materials can be tuned.
In situ dispersion of non-aqueous Fe3O4 nanocolloids by microdroplet coalescence and their use in the preparation of magnetic composite particles
Authors: Du Le , Wang Yujun , Xu Jianhong , Shen Chun , Luo Guangsheng
Published: May 2016

Monodispersity and size uniformity are critical issues for nanoparticles, especially for the inorganic particles dispersed in organic carriers serving as the precursor of composites.
Current status and challenges of biohydrogels for applications as supercapacitors and secondary batteries
Authors: Armelin Elaine , Pérez-Madrigal Maria M. , Alemán Carlos , Díaz David Díaz
Published: May 2016

The emerging use of biohydrogels for the fabrication of either conductive electrolytes or electrodes for battery science and technology.
High nuclearity carbonyl clusters as near-IR contrast agents for photoacoustic in vivo imaging
Authors: Lam Zhiyong , Balasundaram Ghayathri , Kong Kien Voon , Chor Bo Yang , Goh Douglas , Khezri Bahareh , Webster Richard D. , Leong Weng Kee , Olivo Malini
Published: May 2016

The high nuclearity osmium carbonyl cluster Na2[Os10(μ6-C)(CO)24] is a good near-IR photoacoustic contrast agent for full body imaging.
A two-photon ratiometric ESIPT probe for the discrimination of different palladium species and its application in bioimaging
Authors: Luo Weifang , Liu Weisheng
Published: May 2016

A two-photon ratiometric ESIPT probe for the discrimination of different palladium species which could be used for bioimaging.
Dual responsive mesoporous silica nanoparticles for targeted co-delivery of hydrophobic and hydrophilic anticancer drugs to tumor cells
Authors: Chen Xin , Liu Zhongning
Published: May 2016

Dual responsive mesoporous silica nanoparticles integrating stepwise tumor targeting and co-delivery of multiple anticancer drugs were developed to attenuate the drug resistance of cancer cells.
Facile fabrication of amphiphilic AIE active glucan via formation of dynamic bonds: self assembly, stimuli responsiveness and biological imaging
Authors: Wan Qing , Liu Meiying , Xu Dazhuang , Huang Hongye , Mao Liucheng , Zeng Guangjian , Deng Fengjie , Zhang Xiaoyong , Wei Yen
Published: May 2016

A one-pot strategy has been developed for the preparation of stimuli responsive AIE active glucan through formation of a dynamic Schiff base and a phenyl borate.
Biodegradable electronics: cornerstone for sustainable electronics and transient applications
Authors: Tan Mein Jin , Owh Cally , Chee Pei Lin , Kyaw Aung Ko Ko , Kai Dan , Loh Xian Jun
Published: May 2016

Electronic devices have become ubiquitous in modern society and are prevalent in every facet of human activities.
The rapid and dense assembly of solution-processed single-wall carbon nanotube semiconducting films via an acid-based additive in the aqueous dispersion
Authors: Kim Taehoon , Seong Narkhyeon , Ha Jewook , Kim Hyeonggyu , Ha Tae-Jun , Hong Yongtaek
Published: May 2016

A facile method based on the addition of diluted acid into an aqueous SWCNT dispersion significantly improves the deposition rate of a solution-processed SWCNT layer by controlling the chemical states of the dispersion.
An in vitro and in vivo bio-interaction responses and biosafety evaluation of novel Au–ZnTe core–shell nanoparticles
Authors: Dunpall R. , Revaprasadu N.
Published: May 2016

Novel gold–zinc telluride (Au–ZnTe) core–shell nanoparticles were synthesized to support surface modifications for enhanced drug delivery in cancer therapeutics.
Repair or Violation Detection? Pre-Attentive Processing Strategies of Phonotactic Illegality Demonstrated on the Constraint of g-Deletion in German
Authors: Steinberg Johanna , Jacobsen Thomas Konstantin , Jacobsen Thomas
Published: May 2016

Purpose

Effects of categorical phonotactic knowledge on pre-attentive speech processing were investigated by presenting illegal speech input that violated a phonotactic constraint in German called “g-deletion.” The present study aimed to extend previous findings of automatic processing of phonotactic violations and to investigate the role of stimulus context in triggering either an automatic phonotactic repair or a detection of the violation.

Method

The mismatch negativity event-related potential component was obtained in 2 identical cross-sectional experiments with speaker variation and 16 healthy adult participants each. Four pseudowords were used as stimuli, 3 of them phonotactically legal and 1 illegal. Stimuli were contrasted pairwise in passive oddball conditions and presented binaurally via headphones. Results were analyzed by means of mixed design analyses of variance.

Results

Phonotactically illegal stimuli were found to be processed differently compared to legal ones. Results indicate evidence for both automatic repair and detection of the phonotactic violation depending on the linguistic context the illegal stimulus was embedded in.

Conclusions

These findings corroborate notions that categorical phonotactic knowledge is activated and applied even in the absence of attention. Thus, our findings contribute to the general understanding of sublexical phonological processing and may be of use for further developing speech recognition models.

Supplemental Material

https://doi.org/10.23641/asha.14963802
Floating body gate cell with fast write speed for embedded memory applications
Authors: He Weiwei , Chen Jing , Wu Qingqing , Luo Jiexin , Chai Zhan , Huang Jianqiang , Wang Xi
Published: May 2016

Novel two‐transistor embedded memory – floating body gate cell – is implemented on planar SOI CMOS technology without adding extra masks. Since channel current is designed for memory cell write operations, this cell demonstrates ultra‐fast write speed which is comparable with static RAM cell. The decoupled write and read structure ensures small operation power consumption and avoid false read. The low operation voltages of this cell lead to the excellent endurance performance. In addition, retention time is greatly enhanced due to the gate‐to‐drain underlap design.
Dynamic equivalent‐based reliability evaluation of distribution systems with DGs
Authors: Wang Huaizhi , Lin Haofan , Yu Tao , Xu Zhao , Mishra Yateendra
Published: May 2016

This study proposes a novel dynamic reliability network‐equivalent approach (RNEA) for distribution generations (DGs) enhanced distribution system. This method includes a bottom‐up process and a top‐down process, which are developed based on equivalent principle, and the synthesis of both processes yields the reliability performance of any node in the system. In addition, a novel switch zone concept is defined and introduced into the bottom‐up equivalent process as to save the computation cost. Besides, a hybrid restoration model is proposed to account for the practical restoration process in power grids, and solved using particle swarm optimisation. The most significant of the proposed approach over other equivalent methods such as section technique, RNEA, and zone‐branch method is that it provides a more generalised element‐by‐element equivalent approach that can greatly simplify the network for reliability assessment irrespective of the network topology. The proposed methodology has been successfully tested on a real 362‐node urban distribution system in China, with and without DGs considered.
Research and application of multiple STATCOMs to improve the stability of AC/DC power systems in China Southern Grid
Authors: Rao Hong , Xu Shukai , Zhao Yong , Hong Chao , Wei Wei , Li Xiaolin , Zhang Jianshe , Song Qiang
Published: May 2016

This study presents the research and application of multiple static synchronous compensators (STATCOMs) in the China Southern Grid (CSG) to enhance the stability of its receiving‐end power system. In this research, a practical methodology is developed for the optimal allocation of STATCOMs in a complex power system through both static and dynamic approaches. The allocation scheme for installing multiple STATCOMs in the CSG is determined using the proposed process. ±200 MVAr STATCOMs are developed based on cascaded H‐bridge converters connected in the delta structure. A special system‐level control strategy for fast voltage recovery applications is introduced in this study, and field test results and application effects are presented. Results of the real‐time digital simulation are introduced to verify the application effects in the case where multiple STATCOMs are connected to the grid. Field test results and analysis of the recorded data for the system faults during actual operation also verify the application effects of multiple STATCOMs in the CSG.
H‐infinity based non‐linear sliding mode controller for frequency regulation in interconnected power systems with constant and time‐varying delays
Authors: Prasad Sheetla , Purwar Shubhi , Kishor Nand
Published: May 2016

Load frequency control (LFC) scheme communicates from remote terminal units to control centre, followed by control centre action on the corresponding plant units. The conventional dedicated communication channels have constant time delay, while open communication channel, i.e. shared one has time‐varying delay. These delays degrade the dynamic performance or even lead to system instability. In an interconnected system, communications delays cannot be ignored and therefore the time delay is introduced in the area control error signal. In this study, a time delay‐dependent H∞‐based non‐linear sliding mode controller for LFC scheme has been proposed for N area power system. The approach uses Lyapunov–Krasovskii functional based on time delay‐dependent stability criteria and linear matrix inequalities optimisation. Simulation studies are presented for two‐area LFC scheme against step and random step load disturbance and generation rate constraints. Comparison is also made with recently reported; two‐term controller design. The simulation results establish the superiority and applicability of the proposed design for LFC application. The results illustrate that the proposed scheme can effectively enhance the frequency stability via improving the damping of the system.
Image enhancement based on intuitionistic fuzzy sets theory
Authors: Deng He , Sun Xianping , Liu Maili , Ye Chaohui , Zhou Xin
Published: May 2016

Enhancement of images with weak edges faces great challenges in imaging applications. In this study, the authors propose a novel image enhancement approach based on intuitionistic fuzzy sets. The proposed method first divides an image into sub‐object and sub‐background areas, and then successively implements new fuzzification, hyperbolisation, and defuzzification operations on each area. In this way, an enhanced image is obtained, where the visual quality of region of interest (ROI) is significantly improved. Several types of images are utilised to validate the proposed method with respect to the enhancement performance. Experimental results demonstrate that the proposed algorithm not only works more stably for different types of images, but also has better enhancement performance, in comparison to conventional methods. This is a great merit of such design for discerning specific ROIs.
Fast‐efficient shape error concealment technique based on block classification
Authors: Hsia Shih‐Chang , Hsiao Cheng Hung
Published: May 2016

This study presents a fast‐efficient error concealment method for recovering information related to shape. The proposed technique comprises block classification, edge direction interpolation and filtering interpolation. Missing blocks are classified into four categories: transparent, opaque, edge and isolated blocks. Most of the computation is spent on edge blocks and isolated blocks to maximise the cost and performance tradeoff. For the recovery of edge blocks, the edge slope is computed by referring to the nearest available block, from which the missing shape is interpolated parallel to the edge. Isolated blocks are dealt with using a cascade filter to approximate the actual shape. Experimental results show that the proposed method provides better cost performance in the restoration of shapes than that afforded by comparable algorithms, both in numerical parameters and the resulting shapes. The processing speed is approximately two to three times faster than previous methods and low computational load makes the proposed technique applicable to real‐time MPEG‐4 systems.
Fast Coiflet magnetic field integral equation for scattering from open rough surfaces
Authors: Zhang Lisha , Pan Guangwen George
Published: May 2016

The magnetic field integral equation (MFIE) is solved by Coiflets for rough surface scattering. The vanishing moments of Coiflets provide one‐point quadrature, which slashes the matrix filling effort from O(N2) to O(N), and consequently reduces the complexity scaling in between O(N) and O(Nlog N) for problems with unknowns up to 106. The bi‐conjugate solver converges very fast owing to the well‐posedness of the MFIE. The resulting impedance matrix is further sparsified by the matrix‐formed standard fast wavelet transform. By properly selecting multiresolution levels of the total transformation matrix, the solution precision can be enhanced while matrix sparsity and memory consumption have not been noticeably sacrificed. Numerical results are compared with the Rao‐Wilton‐Glisson multilevel fast multipole algorithm (RWG‐MLFMA) based commercial software FEKO, and good agreement is observed.
Analysis and implementation of a novel high step‐up DC–DC converter with low switch voltage stress and reduced diode voltage stress
Authors: Chen Yie‐Tone , Lu Zong‐Xing , Liang Ruey‐Hsun , Hung Chung‐Wen
Published: May 2016

A new high step‐up dc–dc converter is proposed in this study. This new high step‐up converter utilises the input voltage, clamped‐capacitor, and the secondary side of the coupled‐inductor to charge the switched‐capacitor and the secondary side of the coupled inductor also charges two multiplier capacitors in parallel during the turn‐on interval of the switch. The input voltage, coupled‐inductor, and multiplier capacitors are in series connection to the output to accomplish the purpose of high voltage gain during the turn‐off interval of the switch. By adjusting the turns ratio of the coupled inductors, the proposed circuit does not need to be operated at high duty cycle to achieve the high voltage gain. The voltage stress of the switch and diodes can be decreased to cut down the cost. Moreover, the energy of the leakage inductance can be recovered to reduce the voltage spike of the switch. Therefore, the switch with lower conduction resistance can be applied to reduce the conduction loss and increase the efficiency. Finally, simulation and experiments are conducted. A prototype circuit with input voltage of 24 V, output voltage of 400 V, and output power of 200 W is implemented to validate the property of the proposed converter.
Irregular Liesegang-type patterns in gas phase revisited. I. Experimental setup, data processing, and test of the spacing law
Authors: Torres-Guzmán José C. , Buhse Thomas , de la Calleja Elsa María , González-Espinoza Alfredo , Martínez-Mekler Gustavo , Montoya-Nava Fernando , Ramírez-Álvarez Elizeth , Rivera-Islas Marco , Rodríguez-Álvarez Aurora , Müller Markus F.
Published: May 2016

Since the early work on Liesegang rings in gels, they have been a reference point for the study of pattern formation in chemical physics. Here we present a variant of the Liesegang experiment in gas phase, where ammonia and hydrochloric acid react within a glass tube producing a precipitate, which deposits along the tube wall producing a spatial pattern. With this apparently simple experiment a wide range of rich phenomenon can be observed due to the presence of convective flows and irregular dynamics reminiscent of turbulent behavior, for which precise measurements are scarce. In this first part of our work, we describe in detail the experimental setup, the method of data acquisition, the image processing, and the procedure used to obtain an intensity profile, which is representative of the amount of precipitate deposited at the tube walls. Special attention is devoted to the techniques rendering a data series reliable for statistical studies and model building, which may contribute to a characterization and understanding of the pattern formation phenomenon under consideration. As a first step in this direction, based on our data, we are able to show that the observed band pattern follows, with slight deviations, the spacing law encountered in common Liesegang rings, despite that the experimental conditions are very different. A further statistical correlation analysis of the data constitutes Paper II of this research.
Characterizing dynamic hysteresis and fractal statistics of chaotic two-phase flow and application to fuel cells
Authors: Burkholder Michael B. , Litster Shawn
Published: May 2016

In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurable regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.
First-principles Hubbard U approach for small molecule binding in metal-organic frameworks
Authors: Mann Gregory W. , Lee Kyuho , Cococcioni Matteo , Smit Berend , Neaton Jeffrey B.
Published: May 2016

We apply first-principles approaches with Hubbard U corrections for calculation of small molecule binding energetics to open-shell transition metal atoms in metal-organic frameworks (MOFs). Using density functional theory with van der Waals dispersion-corrected functionals, we determine Hubbard U values ab initio through an established linear response procedure for M-MOF-74, for a number of different metal centers (M = Ti, V, Cr, Mn, Fe, Co, Ni, and Cu). While our ab initio U values differ from those used in previous work, we show that they result in lattice parameters and electronic contributions to CO2-MOF binding energies that lead to excellent agreement with experiments and previous results, yielding lattice parameters within 3%. In addition, U-dependent calculations for an example system, Co-MOF-74, suggest that the CO2 binding energy grows monotonically with the value of Hubbard U, with the binding energy shifting 4 kJ/mol (or 0.041 eV) over the range of U = 0-5.4 eV. These results provide insight into an approximate but computationally efficient means for calculation of small molecule binding energies to open-shell transition metal atoms in MOFs and suggest that the approach can be predictive with good accuracy, independent of the cations used and the availability of experimental data.
Investigation on subsonic to supersonic flow around a sphere at low Reynolds number of between 50 and 300 by direct numerical simulation
Authors: Nagata T. , Nonomura T. , Takahashi S. , Mizuno Y. , Fukuda K.
Published: May 2016

In this study, analysis of flow properties around a sphere and its aerodynamic coefficients in the high-Mach-and-low-Reynolds-numbers conditions is carried out by direct numerical simulations solving the three-dimensional compressible Navier–Stokes equations. The calculation is performed on a boundary-fitted coordinate system with a high-order scheme of sufficient accuracy. The analysis is conducted by assuming a rigid sphere with a Reynolds number of between 50 and 300, based on the diameter of the sphere and the freestream velocity and a freestream Mach number of between 0.3 and 2.0, together with the adiabatic wall boundary condition. The calculation shows the following yields: (1) unsteady fluctuation of hydrodynamic forces become smaller as the Mach number increases under the same Reynolds number condition, (2) the drag coefficient increases with the Mach number due to an increase in the pressure drag by the shock wave, and (3) an accurate prediction of the drag coefficient in the supersonic regime using traditional models might be difficult.
Active control of vortex-induced vibrations of a circular cylinder using windward-suction- leeward-blowing actuation
Authors: Wang Chenglei , Tang Hui , Yu Simon C. M. , Duan Fei
Published: May 2016

This paper studies the control of two-dimensional vortex-induced vibrations (VIVs) of a single circular cylinder at a Reynolds number of 100 using a novel windward-suction-leeward-blowing (WSLB) concept. A lattice Boltzmann method based numerical framework is adopted for this study. Both open-loop and closed-loop controls are implemented. In the open-loop control, three types of actuation arrangements, including the pure suction on the windward side of the cylinder, the pure blowing on the leeward side, and the general WSLB on both sides, are implemented and compared. It is found that the general WSLB is the most effective, whereas the pure suction is the least effective. In the closed-loop control, the proportional (P), integral (I), and proportional-integral (PI) control schemes are applied to adjust the WSLB velocities according to the flow information obtained from a sensor. The effects of four key control parameters including the proportional gain constant, the integral gain constant, the length of data history used for the feedback, and the location of the sensor are investigated. It is found that the use of only P control fails to completely suppress the VIV, the use of only I control can achieve the complete suppression, and the PI control performs the best in terms of both the control effectiveness and efficiency. In the PI control, there exists an optimal length of data history for the feedback, at which the VIV control is the most efficient. There also exist the minimum required WSLB velocities for the VIV suppression, independent of the control schemes. Moreover, it is found that the VIV control is independent of the sensor location.
Interaction of a two-layer vortex pair with a submerged cylindrical obstacle in a two layer rotating fluid
Authors: Ryzhov Eugene A. , Sokolovskiy Mikhail A.
Published: May 2016

We consider the dynamics of a two-layer compensated vortex pair (heton) interacting with a submerged cylindrical obstacle of small height located in the lower layer of a two-layer fluid in the f-plane. The pair consists of two counter-rotating vortices of equal strengths each located in different layers of the two-layer rotating fluid. We make use of two approaches. The first one considers a model of point vortices, and the second one assumes the vortices as finite-core vorticity patches analyzed by means of contour dynamics techniques. The point vortex model features two regimes of the pair’s motion: an unbounded motion as the pair advances to infinity after being deflected by the cylindrical obstacle and an oscillatory motion inside a bounded region near the cylindrical obstacle. The oscillations, in turn, are of two types. The first corresponds to a finite yet unpredictable number of vortex revolutions near the cylinder, and the second results in an infinite number of revolutions. By exploiting contour dynamics techniques, we obtain very similar unbounded dynamics of a distributed vorticity heton given relatively strong stratification. An important feature of this dynamics is that the contours associated with the pair hold almost unperturbed signifying sufficient stability. By decreasing stratification, we observe complicated dynamics involving vorticity redistribution and vortex splitting.
Rising of a single Taylor drop in a stagnant liquid—2D laminar flow and axisymmetry limits
Authors: Direito F. J. N. , Campos J. B. L. M. , Miranda J. M.
Published: May 2016

A numerical (computational fluid dynamics (CFD)) study concerning the rise of individual liquid Taylor drops through vertical columns of stagnant heavier liquids is presented in this paper. CFD simulations were performed in Ansys Fluent, using its implementation of volume of fluid method, assuming the flow to be axisymmetric and laminar. Different physical conditions were tested, corresponding to different combinations of relevant dimensionless parameters and the numerical method was validated through experimental data available in the literature. The viscosity ratio between the lighter and the heavier liquid was within the range 0.01–40 and Eötvös number was between 8 and 30. Morton number was within the interval of 2.32 × 10−6–100. Froude number results were compared to data from a literature correlation. The accordance is acceptable for the ranges studied. Velocity profiles in significant regions are reported (drop nose, drop bottom and continuous phase liquid film). The influence of changing one dimensionless parameter alone was assessed. For small and large viscosity ratios, axisymmetric behavior is not a valid assumption.
Mechanism underlying Kármán vortex street breakdown preceding secondary vortex street formation
Authors: Dynnikova G. Ya. , Dynnikov Ya. A. , Guvernyuk S. V.
Published: May 2016

The Kármán street that develops behind a bluff body transforms in the far wake into a secondary vortex street of lower frequency and stronger vortices. Before this transformation, the primary street decays. This interesting phenomenon was investigated in a number of experimental and theoretical studies. Much of that work is devoted to studying the reasons for the formation of the secondary street and its frequency characteristics. Reasons for the decay of the primary street are not well understood. In this work, the mechanism underlying the breaking of the primary vortex street is studied. A qualitative explanation of this process is presented wherein a region of heightened density of the dipole moment forms. This region moves relative to the Kármán vortices so that its distance from the body remains constant. In this region, the Kármán vortex street collapses.
Dip-coating of yield stress fluids
Authors: Maillard M. , Bleyer J. , Andrieux A. L. , Boujlel J. , Coussot P.
Published: May 2016

We review and discuss the characteristics of dip-coating of yield stress fluids on the basis of theoretical considerations, numerical simulations of the flow in the bath, and experimental data with different materials. We show that in general, due to the yield stress, viscous dissipations are sufficiently large for capillary effects to be negligible in the process. Dip-coating with yield stress fluids is thus essentially governed by an equilibrium between viscous and gravity effects. In contrast with simple liquids, the coated thickness is uniform and remains fixed to the plate. At low velocities, it appears to tend to a value significantly smaller than the Derjaguin and Levi prediction [B. V. Derjaguin and S. M. Levi, Film Coating Theory (The Focal Press, London, 1964)], i.e., critical thickness of stoppage of a free surface flow along a vertical plate. We show that this comes from the fact that in the bath only a relatively small layer of fluid is in its liquid regime along the moving plate, while the rest of the material is in a solid regime. From numerical simulations, we describe the general trends of this liquid layer, and in particular, its thickness as a function of the rheological characteristics and plate velocity. We finally propose a model for the dip-coating of yield stress fluid, assuming that the solid volume of fluid finally fixed to the plate results from the mass flux of the liquid layer in the bath minus a mass flux due to some downward flow under gravity in the transition zone. A good agreement between this model and experimental data is found for a fluid with a yield stress larger than 20 Pa.
Cohesive energy and structural parameters of binary oxides of groups IIA and IIIB from diffusion quantum Monte Carlo
Authors: Santana Juan A. , Krogel Jaron T. , Kent Paul R. C. , Reboredo Fernando A.
Published: May 2016

We have applied the diffusion quantum Monte Carlo (DMC) method to calculate the cohesive energy and the structural parameters of the binary oxides CaO, SrO, BaO, Sc2O3, Y2O3, and La2O3. The aim of our calculations is to systematically quantify the accuracy of the DMC method to study this type of metal oxides. The DMC results were compared with local, semi-local, and hybrid Density Functional Theory (DFT) approximations as well as with experimental measurements. The DMC method yields cohesive energies for these oxides with a mean absolute deviation from experimental measurements of 0.18(2) eV, while with local, semi-local, and hybrid DFT approximations, the deviation is 3.06, 0.94, and 1.23 eV, respectively. For lattice constants, the mean absolute deviations in DMC, local, semi-local, and hybrid DFT approximations are 0.017(1), 0.07, 0.05, and 0.04 Å, respectively. DMC is a highly accurate method, outperforming the DFT approximations in describing the cohesive energies and structural parameters of these binary oxides.
A cylindrical quadrupole ion trap in combination with an electrospray ion source for gas-phase luminescence and absorption spectroscopy
Authors: Stockett Mark H. , Houmøller Jørgen , Støchkel Kristian , Svendsen Annette , Brøndsted Nielsen Steen
Published: May 2016

A relatively simple setup for collection and detection of light emitted from isolated photo-excited molecular ions has been constructed. It benefits from a high collection efficiency of photons, which is accomplished by using a cylindrical ion trap where one end-cap electrode is a mesh grid combined with an aspheric condenser lens. The geometry permits nearly 10% of the emitted light to be collected and, after transmission losses, approximately 5% to be delivered to the entrance of a grating spectrometer equipped with a detector array. The high collection efficiency enables the use of pulsed tunable lasers with low repetition rates (e.g., 20 Hz) instead of continuous wave (cw) lasers or very high repetition rate (e.g., MHz) lasers that are typically used as light sources for gas-phase fluorescence experiments on molecular ions. A hole has been drilled in the cylinder electrode so that a light pulse can interact with the ion cloud in the center of the trap. Simulations indicate that these modifications to the trap do not significantly affect the storage capability and the overall shape of the ion cloud. The overlap between the ion cloud and the laser light is basically 100%, and experimentally >50% of negatively charged chromophore ions are routinely photodepleted. The performance of the setup is illustrated based on fluorescence spectra of several laser dyes, and the quality of these spectra is comparable to those reported by other groups. Finally, by replacing the optical system with a channeltron detector, we demonstrate that the setup can also be used for gas-phase action spectroscopy where either depletion or fragmentation is monitored to provide an indirect measurement on the absorption spectrum of the ion.
Reaction rates and kinetic isotope effects of H2 + OH → H2O + H
Authors: Meisner Jan , Kästner Johannes
Published: May 2016

We calculated reaction rate constants including atom tunneling of the reaction of dihydrogen with the hydroxy radical down to a temperature of 50 K. Instanton theory and canonical variational theory with microcanonical optimized multidimensional tunneling were applied using a fitted potential energy surface [J. Chen et al., J. Chem. Phys. 138, 154301 (2013)]. All possible protium/deuterium isotopologues were considered. Atom tunneling increases at about 250 K (200 K for deuterium transfer). Even at 50 K the rate constants of all isotopologues remain in the interval 4 ⋅ 10−20 to 4 ⋅ 10−17 cm3 s−1, demonstrating that even deuterated versions of the title reaction are possibly relevant to astrochemical processes in molecular clouds. The transferred hydrogen atom dominates the kinetic isotope effect at all temperatures.
Simple posterior frequency correction for vibrational spectra from molecular dynamics
Authors: Tikhonov Denis S.
Published: May 2016

Vibrational spectra computed from molecular dynamics simulations with large integration time steps suffer from nonphysical frequency shifts of signals [M. Praprotnik and D. Janežič, J. Chem. Phys. 122, 174103 (2005)]. A simple posterior correction technique was developed for compensation of this behavior. It performs through replacement of abscissa in the calculated spectra using following formula: νcorrected=2⋅1−cos(2π⋅Δt⋅νinitial)2π⋅Δt, where ν are initial and corrected frequencies and Δt is the MD simulation time step. Applicability of this method was tested on gaseous infrared spectra of hydrogen fluoride and formic acid.
GaInSb/InAs/AlSb quantum wells with InSb- and GaAs-like interfaces investigated by temperature- and magnetic field-dependent photoluminescence
Authors: Chen Xiren , Xing Junliang , Zhu Liangqing , Zha F.-X. , Niu Zhichuan , Guo Shaoling , Shao Jun
Published: May 2016

GaInSb/InAs/AlSb quantum wells (QWs) with typical InSb- and GaAs-like interfaces (IFs) are investigated by temperature- and magnetic field-dependent photoluminescence (PL), respectively. The results show that (i) as temperature rises the PL energy of the QWs with either InSb- or GaAs-like IFs blueshifts slightly below 50 K but redshifts above and broadens rapidly, and the mechanism behind this is correlated to the IF roughness-related layer thickness fluctuation equivalent to a localization energy of about 9.5 meV; (ii) the PL diminishes monotonously as magnetic field rises except for the delocalized PL process of the InSb-like IF QWs, and the magnetic field-induced PL quenching is attributed to the IF roughness-induced electron-hole separation in the type-II QWs; and (iii) the magnetic field-dependent PL energy follows a typical excitonic diamagnetic shift for both located and dislocated states, and the deduced exciton binding energy, reduced effective mass, and average wavefunction extent are insensitive to the IF type. Comparison of different IF-type GaInSb/InAs QWs indicates that while the PL of the InSb-like IF sample contains type-I component as the IF confines heavy holes and acts as pseudo-barrier for electrons, leading to the coexistence of electrons and holes at the IFs, the IF-type does not affect the carrier localization and the in-plane excitonic behavior obviously.
Refractive index modulation of Sb70Te30 phase-change thin films by multiple femtosecond laser pulses
Authors: Lei Kai , Wang Yang , Jiang Minghui , Wu Yiqun
Published: May 2016

In this study, the controllable effective refractive index modulation of Sb70Te30 phase-change thin films between amorphous and crystalline states was achieved experimentally by multiple femtosecond laser pulses. The modulation mechanism was analyzed comprehensively by a spectral ellipsometer measurement, surface morphology observation, and two-temperature model calculations. We numerically demonstrate the application of the optically modulated refractive index of the phase-change thin films in a precisely adjustable color display. These results may provide further insights into ultrafast phase-transition mechanics and are useful in the design of programmable photonic and opto-electrical devices based on phase-change memory materials.
In-situ observations of flux ropes formed in association with a pair of spiral nulls in magnetotail plasmas
Authors: Guo Ruilong , Pu Zuyin , Chen Li-Jen , Fu Suiyan , Xie Lun , Wang Xiaogang , Dunlop Malcolm , Bogdanova Yulia V. , Yao Zhonghua , Xiao Chijie , He Jiansen , Fazakerley Andrew N.
Published: May 2016

Signatures of secondary islands are frequently observed in the magnetic reconnection regions of magnetotail plasmas. In this paper, magnetic structures with the secondary-island signatures observed by Cluster are reassembled by a fitting-reconstruction method. The results show three-dimensionally that a secondary island event can manifest the flux rope formed with an As-type null and a Bs-type null paired via their spines. We call this As-spine-Bs-like configuration the helically wrapped spine model. The reconstructed field lines wrap around the spine to form the flux rope, and an O-type topology is therefore seen on the plane perpendicular to the spine. Magnetized electrons are found to rotate on and cross the fan surface, suggesting that both the torsional-spine and the spine-fan reconnection take place in the configuration. Furthermore, detailed analysis implies that the spiral nulls and flux ropes were locally generated nearby the spacecraft in the reconnection outflow region, indicating that secondary reconnection may occur in the exhaust away from the primary reconnection site.
The study of heat flux for disruption on experimental advanced superconducting tokamak
Authors: Yang Zhendong , Fang Jianan , Gong Xianzu , Gan Kaifu , Luo Jiarong , Zhao Hailin , Cui Zhixue , Zhang Bin , Chen Meiwen
Published: May 2016

Disruption of the plasma is one of the most dangerous instabilities in tokamak. During the disruption, most of the plasma thermal energy is lost, which causes damages to the plasma facing components. Infrared (IR) camera is an effective tool to detect the temperature distribution on the first wall, and the energy deposited on the first wall can be calculated from the surface temperature profile measured by the IR camera. This paper concentrates on the characteristics of heat flux distribution onto the first wall under different disruptions, including the minor disruption and the vertical displacement events (VDE) disruption. Several minor disruptions have been observed before the major disruption under the high plasma density in experimental advanced superconducting tokamak. During the minor disruption, the heat fluxes are mainly deposited on the upper/lower divertors. The magnetic configuration prior to the minor disruption is a lower single null with the radial distance between the two separatrices in the outer midplane dRsep = −2 cm, while it changes to upper single null (dRsep = 1.4 cm) during the minor disruption. As for the VDE disruption, the spatial distribution of heat flux exhibits strong toroidal and radial nonuniformity, and the maximum heat flux received on the dome plate can be up to 11 MW/m2.