bluuebunny/crossref_metadata_2025 huggingface dataset:
Tunable terahertz fishnet metamaterials based on thin nematic liquid crystal layers for fast switching
Authors: Zografopoulos Dimitrios C. , Beccherelli Romeo
Published: August 2015

The electrically tunable properties of liquid-crystal fishnet metamaterials are theoretically investigated in the terahertz spectrum. A nematic liquid crystal layer is introduced between two fishnet metallic structures, forming a voltage-controlled metamaterial cavity. Tuning of the nematic molecular orientation is shown to shift the magnetic resonance frequency of the metamaterial and its overall electromagnetic response. A shift higher than 150 GHz is predicted for common dielectric and liquid crystalline materials used in terahertz technology and for low applied voltage values. Owing to the few micron-thick liquid crystal cell, the response speed of the tunable metamaterial is calculated as orders of magnitude faster than in demonstrated liquid-crystal based non-resonant terahertz components. Such tunable metamaterial elements are proposed for the advanced control of electromagnetic wave propagation in terahertz applications.
Improving the accuracy of the k-shell method by removing redundant links: From a perspective of spreading dynamics
Authors: Liu Ying , Tang Ming , Zhou Tao , Do Younghae
Published: August 2015

Recent study shows that the accuracy of thek-shell method in determining node coreness in a spreading process is largely impacted due to the existence of core-like group, which has a largek-shell index but a low spreading efficiency. Based on the analysis of the structure of core-like groups in real-world networks, we discover that nodes in the core-like group are mutually densely connected with very few out-leaving links from the group. By defining a measure of diffusion importance for each edge based on the number of out-leaving links of its both ends, we are able to identify redundant links in the spreading process, which have a relatively low diffusion importance but lead to form the locally densely connected core-like group. After filtering out the redundant links and applying thek-shell method to the residual network, we obtain a renewed corenessksfor each node which is a more accurate index to indicate its location importance and spreading influence in the original network. Moreover, we find that the performance of the ranking algorithms based on the renewed coreness are also greatly enhanced. Our findings help to more accurately decompose the network core structure and identify influential nodes in spreading processes.
Label-Free Biosensing with High Selectivity in Complex Media using Microtoroidal Optical Resonators
Authors: Ozgur Erol , Toren Pelin , Aktas Ozan , Huseyinoglu Ersin , Bayindir Mehmet
Published: August 2015

Although label-free biosensors comprised of optical microcavities inherently possess the capability of resolving molecular interactions at individual level, this extreme sensitivity restricts their convenience for large scale applications by inducing vulnerability towards non-specific interactions that readily occur within complex media. Therefore, the use of optical microresonators for biosensing is mostly limited within strictly defined laboratory conditions, instead of field applications as early detection of cancer markers in blood, or identification of contamination in food. Here, we propose a novel surface modification strategy suitable for but not limited to optical microresonator based biosensors, enabling highly selective biosensing with considerable sensitivity as well. Using a robust, silane-based surface coating which is simultaneously protein resistant and bioconjugable, we demonstrate that it becomes possible to perform biosensing within complex media, without compromising the sensitivity or reliability of the measurement. Functionalized microtoroids are successfully shown to resist nonspecific interactions, while simultaneously being used as sensitive biological sensors. This strategy could pave the way for important applications in terms of extending the use of state-of-the-art biosensors for solving problems similar to the aforementioned.
Improved human visuomotor performance and pupil constriction after choline supplementation in a placebo-controlled double-blind study
Authors: Naber Marnix , Hommel Bernhard , Colzato Lorenza S.
Published: August 2015

Only few nutrients are known to enhance cognition. Here we explore whether visuomotor performance can be improved through the intake of the nutrient choline, an essential chemical compound in a vertebrate’s diet. Choline is abundant in for example eggs and shrimps and many animal studies suggest that it serves as a cognitive enhancer. As choline is important for the communication between motor neurons and the control of skeletal muscles, we assumed that choline supplementation may have positive effects on action coordination in humans. A group of twenty-eight individuals ingested two grams of choline bitartrate or a placebo in two separate sessions. Seventy minutes post ingestion, participants performed a visuomotor aiming task in which they had to rapidly hit the centers of targets. Results showed that participants hit targets more centrally after choline supplementation. Pupil size (a cognition-sensitive biomarker) also significantly decreased after choline intake and correlated positively with the hit distance to the targets and the number of target misses and negatively with reaction times. These findings point to a choline-induced bias towards action precision in the trade-off between speed and accuracy. The changes in pupil size suggest that choline uptake alters cholinergic functions in the nervous system.
Derivation of a fifteen gene prognostic panel for six cancers
Authors: Khirade Mamata F. , Lal Girdhari , Bapat Sharmila A.
Published: August 2015

The hallmarks of cancer deem biological pathways and molecules to be conserved. This approach may be useful for deriving a prognostic gene signature. Weighted Gene Co-expression Network Analysis of gene expression datasets in eleven cancer types identified modules of highly correlated genes and interactive networks conserved across glioblastoma, breast, ovary, colon, rectal and lung cancers, from which a universal classifier for tumor stratification was extracted. Specific conserved gene modules were validated across different microarray platforms and datasets. Strikingly, preserved genes within these modules defined regulatory networks associated with immune regulation, cell differentiation, metastases, cell migration, metastases, oncogenic transformation and resistance to apoptosis and senescence, with AIF1 and PRRX1 being suggested to be master regulators governing these biological processes. A universal classifier from these conserved networks enabled execution of common set of principles across different cancers that revealed distinct, differential correlation of biological functions with patient survival in a cancer-specific manner. Correlation analysis further identified a panel of 15 risk genes with potential prognostic value, termed as the GBOCRL-IIPr panel [(GBM-Breast-Ovary-Colon-Rectal-Lung)–Immune–Invasion–Prognosis], that surprisingly, were not amongst the master regulators or important network hubs. This panel may now be integrated in predicting patient outcomes in the six cancers.
A microporous metal–organic framework with polarized trifluoromethyl groups for high methane storage
Authors: Chang Ganggang , Li Bin , Wang Hailong , Bao Zongbi , Yildirim Taner , Yao Zizhu , Xiang Shengchang , Zhou Wei , Chen Banglin
Published: August 2015

A novel NbO-type metal–organic framework UTSA-88a with polarized trifluoromethyl groups exhibits a notably high methane storage capacity of 248 cm3 (STP) cm−3 and a working capacity of 185 cm3 (STP) cm−3.
Two-dimensional covalent triazine framework as an ultrathin-film nanoporous membrane for desalination
Authors: Lin Li-Chiang , Choi Jongwon , Grossman Jeffrey C.
Published: August 2015

A bottom-up approach for designing promising RO desalination membranes using highly tunable two-dimensional covalent triazine frameworks (CTFs).
Correction: Thymidylate synthase inspired biomodel reagent for the conversion of uracil to thymine
Authors: Singh Palwinder , Kumar Arun , Kaur Sukhmeet , Singh Amrinder
Published: August 2015

Correction for ‘Thymidylate synthase inspired biomodel reagent for the conversion of uracil to thymine’ by Palwinder Singh et al., Chem. Commun., 2015, 51, 9961–9964.
Radiation-induced formation of Co3O4 nanoparticles from Co2+(aq): probing the kinetics using radical scavengers
Authors: Alrehaily L. M. , Joseph J. M. , Wren J. C.
Published: August 2015

The kinetics of γ-radiation-induced Co3O4 nanoparticle formation occurs in four distinct stages. Scavengers and [Co2+]0 affect the kinetics in different stages, and consequently influence the final particle sizes. Radiolysis model calculations on the effects of radical scavengers provide insights into their role in controlling particle formation.
Growth of colloidal PbS nanosheets and the enhancement of their photoluminescence
Authors: Jiang Zhoufeng , Bhandari Ghadendra B. , Premathilaka Shashini M. , Khan Simeen , Dimick Douglas M. , Stombaugh Cody , Mandell Angelic , He Yufan , Peter Lu H. , Sun Liangfeng
Published: August 2015

Dual photoluminescence peaks observed during the synthesis of PbS nanosheets reveal their growth mechanism – two-dimensional attachments of the quantum dots.
Enhanced electrochemical performance of a ZnO–MnO composite as an anode material for lithium ion batteries
Authors: Song Min Seob , Nahm Sahn , Cho Won Il , Lee Chongmok
Published: August 2015

A reduced ZnO–MnO composite electrode exhibits improved electrochemical performance as an anode material for lithium ion batteries.
Precipitation and surface adsorption of metal complexes during electropolishing. Theory and characterization with X-ray nanotomography and surface tension isotherms
Authors: Nave Maryana I. , Chen-Wiegart Yu-chen Karen , Wang Jun , Kornev Konstantin G.
Published: August 2015

Using X-ray nano-tomography, a gel-like phase formed at the tungsten surface during electropolishing was discovered and attributed to a complex process of precipitation and sintering of tungsten-based nuclei.
Magneto-electronic properties of graphene nanoribbons with various edge structures passivated by phosphorus and hydrogen atoms
Authors: Yu Z. L. , Wang D. , Zhu Z. , Zhang Z. H.
Published: August 2015

Magneto-electronic properties of graphene nanoribbons with various edge structures passivated by P and H is studied. It shows that if the edge of GNRs is a mixture of zigzag edge and reconstructed Klein edge, they are nonmagnetic for H passivation but obviously magnetic for P passivation.
Assembly and relaxation behaviours of phosphatidylethanolamine monolayers investigated by polarization and frequency resolved SFG-VS
Authors: Wei Feng , Xiong Wei , Li Wenhui , Lu Wangting , Allen Heather C. , Zheng Wanquan
Published: August 2015

Polarization and frequency resolved SFG-VS to distinguish the head/tail groups of lipids, to resolve the assembly and relaxation kinetics of monolayers.
Peptide self-assembly for nanomaterials: the old new kid on the block
Authors: De Santis Emiliana , Ryadnov Maxim G.
Published: August 2015

Self-assembling peptide materials are categorised according to main nanomaterial forms in relation to non-peptide materials.
Enantioselective conjugate addition of cyanide to chalcones catalyzed by a magnesium-Py-BINMOL complex
Authors: Dong Cheng , Song Tao , Bai Xing-Feng , Cui Yu-Ming , Xu Zheng , Xu Li-Wen
Published: August 2015

An efficient asymmetric conjugate addition of trimethylsilyl cyanide (TMSCN) to chalcones, catalyzed by bifunctional Py-BINMOL-Mg complex, with moderate to good enantioselectivities and in good yields, has been realized in this work.
Synthesis and spectroscopic characterization of group 4 post-metallocenes bearing (σ-aryl)-2-phenolate-6-pyridyl and -isoquinolinyl auxiliaries
Authors: Lo Jerry C. Y. , So Loi-Chi , Chan Michael C. W.
Published: August 2015

The title complexes have been characterized for X = F by multinuclear NMR (including [1H,19F]-HMBC) experiments, confirming that the observed 19F–1H (and –13C) coupling occurs with chemical connectivity across C–H⋯F–C interactions, and their catalytic efficiencies for ethylene polymerization have been investigated.
Reduced inorganic sulfur in surface sediment and its impact on benthic environments in offshore areas of NE China
Authors: Sheng Yanqing , Sun Qiyao , Bottrell Simon H. , Mortimer Robert J. G.
Published: August 2015

Geochemical cycling and biological toxicity of sulfur in marine sediments is closely related to the activity of organisms.
Differences in microbial communities and performance between suspended and attached growth anaerobic membrane bioreactors treating synthetic municipal wastewater
Authors: Harb Moustapha , Xiong Yanghui , Guest Jeremy , Amy Gary , Hong Pei-Ying
Published: August 2015

Two different lab-scale anaerobic membrane bioreactors (AnMBRs) were operated under mesophilic conditions (35 °C) and compared based on their microbial community and microbial foulant characteristics.
Fabrication of highly ordered mesoporous silica with the assistance of phosphate
Authors: Wang Yan-Qing , Zheng Chun-Ming , Liu Zhao-Jia , Guo Ming-Lin
Published: August 2015

Highly ordered mesoporous silica was prepared with the assistance of phosphate at a pH of 6.15 using sodium silicate as a silicon source.
Red colored CPL emission of chiral 1,2-DACH-based polymers via chiral transfer of the conjugated chain backbone structure
Authors: Li Fei , Wang Yuxiang , Wang Ziyu , Cheng Yixiang , Zhu Chengjian
Published: August 2015

Chiral polymers incorporating a chiral 1,2-DACH moiety and BODIPY can exhibit strong mirror image Cotton effects and emit red colored CPL signals via the effective chiral transfer of the conjugated polymer chain backbone.
The utilization of post-synthetic modification in opto-electronic polymers: an effective complementary approach but not a competitive one to the traditional direct polymerization process
Authors: Li Qianqian , Li Zhen
Published: August 2015

By presenting some typical examples, the recent progress of opto-electronic polymers is reviewed, which were only accessible from the post-synthetic modification strategy.
Visible-light photoredox catalysis: direct synthesis of fused β-carbolines through an oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade in batch and flow microreactors
Authors: Chandrasekhar D. , Borra Satheesh , Kapure Jeevak Sopanrao , Shivaji Ghule Shailendra , Srinivasulu Gannoju , Maurya Ram Awatar
Published: August 2015

Fused β-carbolines were synthesized via a visible light photoredox catalyzed oxidation/[3 + 2] cycloaddition/oxidative aromatization reaction cascade in batch and flow microreactors.
Cu-Mediated 2,2,2-trifluoroethylation of terminal alkynes using 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123)
Authors: Han En-Jian , Sun Yan , Shen Qian , Chen Qing-Yun , Guo Yong , Huang Yan-Gen
Published: August 2015

Cu-Promoted coupling reactions of HCFC-123 with terminal alkynes give trifluoroethylated internal alkynes.
Influence of ionic strength on the interaction of THA and its Cu(ii) complex with DNA helps to explain studies on various breast cancer cells
Authors: Das Piyal , Bhattacharya Debalina , Karmakar Parimal , Das Saurabh
Published: August 2015

Purpurin, a structural analogue of anthracycline anticancer drugs, was used to understand how environmental changes affect its biophysical interactions with DNA and along with its Cu(ii) complex, the activity it shows on breast cancer cells.
Raising the efficiency of petrolatum deoiling process by using non-polar modifier concentrates separated from paraffin wastes to produce different petroleum products
Authors: Zaky Magdy T. , Mohamed Nermen H. , Farag Amal S. , Soliman Fathi S.
Published: August 2015

Deoiling of crude petrolatum was enhanced by the addition of 1 wt% of non-polar modifier concentrates separated from slack wax waste. The hard waxes produced had larger crystal sizes than those separated without using a modifier.
Direct synthesis of butadiynyl-substituted pyrroles under solvent- and transition metal-free conditions
Authors: Tomilin Denis N. , Pigulski Bartłomiej , Gulia Nurbey , Arendt Agata , Sobenina Lyubov N. , Mikhaleva Al'bina I. , Szafert Sławomir , Trofimov Boris A.
Published: August 2015

The work describes a convenient and highly efficient C–H butadiynylation of substituted pyrroles under mild and solvent-free conditions.
Nickel doped nanohydroxyapatite: vascular endothelial growth factor inducing biomaterial for bone tissue engineering
Authors: Anu Priya B. , Senthilguru K. , Agarwal T. , Gautham Hari Narayana S. N. , Giri S. , Pramanik K. , Pal K. , Banerjee I.
Published: August 2015

Biomaterial induced activation of vascular endothelial growth factor (VEGF) pathway for angiogenesis is now gaining recognition as an effective option for tissue engineering.
Synthesis of exfoliated polystyrene/anionic clay MgAl-layered double hydroxide: structural and thermal properties
Authors: Alansi Amani M. , Alkayali Waed Z. , Al-qunaibit Maha H. , Qahtan Talal F. , Saleh Tawfik A.
Published: August 2015

Synthesis of exfoliated polystyrene/layered double hydroxide (PS/LDH) nanocomposites with enhanced thermal stability.
Systematic development of novel cationic self-nanoemulsifying drug delivery systems of candesartan cilexetil with enhanced biopharmaceutical performance
Authors: Sharma Gajanand , Beg Sarwar , Thanki Kaushik , Katare O. P. , Jain Sanyog , Kohli Kanchan , Singh Bhupinder
Published: August 2015

The current studies entail systematic development, optimization and evaluation of cationic self-nanoemulsifying drug delivery systems (C-SNEDDS) for enhancing the oral bioavailability of candesartan cilexetil.
In situ construction of an SnO2/g-C3N4 heterojunction for enhanced visible-light photocatalytic activity
Authors: Chen Xi , Zhou Banghong , Yang Shuanglei , Wu Hanshuo , Wu Yuxin , Wu Laidi , Pan Jun , Xiong Xiang
Published: August 2015

Herein, the SnO2/g-C3N4 nanocomposite was rationally designed and successfully synthesized via a facile hydrothermal method.
Mechanism of UV-assisted TiO2/reduced graphene oxide composites with variable photodegradation of methyl orange
Authors: Lu Zeyu , Chen Guochang , Hao Wenbin , Sun Guoxing , Li Zongjin
Published: August 2015

TiO2/reduced graphene oxide (TiO2/rGO) composites were synthesized by ultraviolet irradiation method, and the mechanism of TiO2/rGO composites with variable photodegradation efficiency of methyl orange was proposed.
Catalytic hydrogenolysis of glycerol to propanediols: a review
Authors: Wang Yanli , Zhou Jinxia , Guo Xinwen
Published: August 2015

This study summarizes the most significant reports regarding the catalytic hydrogenolysis of glycerol to propanediols.
Electrochemical sensors cleaned by light: a proof of concept for on site applications towards integrated monitoring systems
Authors: Pifferi V. , Soliveri G. , Panzarasa G. , Ardizzone S. , Cappelletti G. , Meroni D. , Falciola L.
Published: August 2015

The potential for on site applications of a SiO2–Ag NPs–TiO2 self-cleaning electrode was demonstrated.
Highly efficient conversion of biomass-derived levulinic acid into γ-valerolactone over Ni/MgO catalyst
Authors: Lv Jinkun , Rong Zeming , Wang Yong , Xiu Jinghai , Wang Yue , Qu Jingping
Published: August 2015

Hydrogenation of levulinic acid (LA) was investigated with Ni/MgO for the production of γ-valerolactone (GVL).
Electron induced chemistry for acetaldehyde
Authors: Vinodkumar Minaxi , Limbachiya Chetan , Desai Hardik , Vinodkumar P. C.
Published: August 2015

A detailed theoretical study is carried out for electron interactions with acetaldehyde (CH3CHO) with impact energies ranging from 0.01 to 5000 eV.
Influence of interface properties on charge density, band edge shifts and kinetics of the photoelectrochemical process in p-type NiO photocathodes
Authors: Liu Qian , Wei Lifang , Yuan Shuai , Ren Xin , Zhao Yin , Wang Zhuyi , Zhang Meihong , Shi Liyi , Li Dongdong , Li Aijun
Published: August 2015

The surface structure of NiO is correlated to observed changes in the band energy, energetic distribution of the trap states density, charge interface transfer, charge transport, and as a result the p-type DSSC device performance.
Novel synthesis of silver/reduced graphene oxide nanocomposite and its high catalytic activity towards hydrogenation of 4-nitrophenol
Authors: Meng Nannan , Zhang Shujie , Zhou Yifeng , Nie Wangyan , Chen Pengpeng
Published: August 2015

Ag/RGO nanocomposites were prepared via reducing AgNO3 in a macroscopic RGO aerogel directly through a convenient impregnation process, which exhibited high activity in the catalytic hydrogenation of 4-nitrophenol.
Rapid prototyping of microchannels with surface patterns for fabrication of polymer fibers
Authors: Goodrich Payton J. , Sharifi Farrokh , Hashemi Nastaran
Published: August 2015

Microfluidic technology has provided innovative solutions to numerous problems, but the cost of fabricating microfluidic channels is impeding its expansion. We created multilayer microchannels significantly quicker and cheaper than current methods.
Coordination behaviour of new open chain and macrocyclic peptidomimetic compounds with copper(ii)
Authors: Wadhavane Prashant D. , Gorla Lingaraju , Ferrer Armando , Altava Belén , Burguete M. Isabel , Izquierdo M. Ángeles , Luis Santiago V.
Published: August 2015

Two valine-derived bis(amino amides) ligands have been prepared and fully characterized.
Graded-lattice AAO photonic crystal heterostructure for high Q refractive index sensing
Authors: Lee Jungmin , Bae Kyuyoung , Kang Gumin , Choi Minjung , Baek Seunghwa , Yoo Do-sik , Lee Chang-Won , Kim Kyoungsik
Published: August 2015

We present a low-cost and versatile high Q colorimetric refractive index sensor based on anodic aluminum oxide (AAO) graded-lattice photonic crystal heterostructure (PCH) template controlled by voltage pulse and electrolyte temperature.
A quantitative definition of hypervalency
Authors: Durrant Marcus C.
Published: August 2015

The concept of hypervalency has had a long but troubled history. Although several attempts have been made to dispense with the concept altogether, it remains in widespread use. By developing a simple but quantitative measure of hypervalency, the concept can be rehabilitated to provide valuable chemical insights in the context of Lewis models.
Identification of diborane(4) with bridging B–H–B bonds
Authors: Chou Sheng-Lung , Lo Jen-Iu , Peng Yu-Chain , Lin Meng-Yeh , Lu Hsiao-Chi , Cheng Bing-Ming , Ogilvie J. F.
Published: August 2015

The irradiation of diborane(6) dispersed in solid neon at 3 K with far-ultraviolet light generated diborane(4), B2H4, with bridging B–H–B bonds.
Liquid marble and water droplet interactions and stability
Authors: Ueno Kazuyuki , Bournival Ghislain , Wanless Erica J. , Nakayama Saori , Giakoumatos Emma C. , Nakamura Yoshinobu , Fujii Syuji
Published: August 2015

The interactions between two individual water droplets were investigated in air using a combination of coalescence rig and high speed video camera.
Phase-selective gelators based on closed-chain glucose derivatives: their applications in the removal of dissolved aniline/nitrobenzene, and toxic dyes from contaminated water
Authors: Zhang Xin , Song Jiefang , Ji Wei , Xu Ning , Gao Ning , Zhang Xuhong , Yu Haitao
Published: August 2015

Easy-to-implement methods were realized with glucose-based gelators for the efficient removal of aniline/nitrobenzene, and toxic dyes from contaminated water.
Template-free ultraspray pyrolysis synthesis of N/Fe-doped carbon microspheres for oxygen reduction electrocatalysis
Authors: Marzorati S. , Vasconcelos J. M. , Ding J. , Longhi M. , Colavita Paula E.
Published: August 2015

Starting from low-cost materials and in the absence of nanostructured templates, C-microspheres with N/Fe active sites for ORR were synthesized via a continuous-flow and scalable USP method.
A hybrid photoelectrode with plasmonic Au@TiO2 nanoparticles for enhanced photoelectrochemical water splitting
Authors: Peerakiatkhajohn Piangjai , Butburee Teera , Yun Jung-Ho , Chen Hongjun , Richards Ryan M. , Wang Lianzhou
Published: August 2015

Herein we present a new p–n heterojunction photoelectrode design utilizing Cu2O and TiO2-P25 loaded with only 1 wt% Au@TiO2 plasmonic core–shell structure for the photoelectrochemical (PEC) process.
Hierarchical hybrid nanostructures of Sn3O4 on N doped TiO2 nanotubes with enhanced photocatalytic performance
Authors: Yu Xin , Wang Longfei , Zhang Jian , Guo Weibo , Zhao Zhenhuan , Qin Yong , Mou Xiaoning , Li Aixue , Liu Hong
Published: August 2015

Sn3O4/N-TiO2 hierarchical hybrid nanostructures exhibit enhanced photocatalytic activity in the decomposition of MO and promote hydrogen evolution from water.
Controllable synthesis of tetrapod gold nanocrystals with precisely tunable near-infrared plasmon resonance towards highly efficient surface enhanced Raman spectroscopy bioimaging
Authors: Cai Jing , Raghavan Vijay , Bai Yu Jie , Zhou Ming Hui , Liu Xiao Li , Liao Chun Yan , Ma Pei , Shi Lei , Dockery Peter , Keogh Ivan , Fan Hai Ming , Olivo Malini
Published: August 2015

Tetrapod gold nanocrystals have been controllably synthesized with tunable near-infrared plasmon resonance.
Electrically conductive and electromagnetic interference shielding of polyethylene composites with devisable carbon nanotube networks
Authors: Jia Li-Chuan , Yan Ding-Xiang , Cui Cheng-Hua , Jiang Xin , Ji Xu , Li Zhong-Ming
Published: August 2015

A segregated structure results in an EMI SE up to 46.4 dB in CNT/polyethylene composites with only 5 wt% CNTs.
Optimum designs of high mobility wireless systems with channel estimation errors
Authors: Sun Ning , Wu Jingxian , Fan Pingzhi
Published: August 2015

This research studies the optimum system designs of high mobility wireless communication systems with imperfect channel state information. In high mobility systems, the channel estimation error is usually inevitable and might have significant impacts on system performance. The impacts of channel estimation errors on system performance are quantified through the development of a spectral efficiency lower bound. With the help of the asymptotic analysis of the channel estimation mean squared error, the spectral efficiency lower bound is expressed as explicit functions of a number of system parameters, such as the maximum Doppler frequency, the percentage of pilots in the transmitted symbols, and the ratio of energy allocated between data symbols and pilot symbols. The optimum pilot percentage and energy allocation factor that jointly maximise the spectral efficiency lower bound are identified through analytical studies. It is discovered that, in term of maximising spectral efficiency, the optimum performance can be achieved by optimising the energy allocation factor when the pilots sample the fast time‐varying fading at its Nyquist rate.
Identification of multi‐input systems using simultaneous perturbation by pseudorandom input signals
Authors: Tan Ai Hui , Barker H. Anthony , Godfrey Keith R.
Published: August 2015

This study describes how sets of spectrally independent and uncorrelated pseudorandom perturbation signals created by a freely available MATLAB program may be used to simultaneously perturb the inputs of multi‐input systems to facilitate their identification. It is shown that with appropriate choices of signals with periods N, N /2, N /4 and so on, the signals in a set have no common harmonics over the common period N, and that a very large number of sets are available in the program. The ways in which these signals may be applied is described and illustrated by two application examples.
Potential feedback control for the power control in wireless sensor networks
Authors: Phan Dat Duong , Moulay Emmanuel , Coirault Patrick , Poussard Anne‐Marie , Vauzelle Rodolphe
Published: August 2015

The aim of this study is to develop a new feedback stabilisation strategy involving a non‐linear potential feedback control (PFC) for scalar discrete‐time systems with disturbances by using Lyapunov functions. The main interest of the PFC is to achieve the stabilisation with a constraint on the state space. The authors apply this strategy for the uplink power control in a real wireless sensor network and compare with the adaptive transmission power control (ATPC) usually used in telecommunications. A study of the energy saving is also provided.
Observer design for a class of non‐linear systems with linearisable error dynamics
Authors: Boutat Driss , Liu Da‐Yan
Published: August 2015

This study aims to study the existence of a change of coordinates which permits to transform a class of non‐linear dynamical systems into the so‐called non‐linear observer canonical form. Moreover, an algorithm used to construct such a change of coordinates is given. Based on this form, the authors can design an observer with a linear error dynamic. This study is motivated by the results obtained by Krener and Respondek in 1985, where they studied the existence of change of coordinates for a class of multi‐outputs non‐linear systems. In 1989, Xia and Gao improved their work. The objective of this study is to show that the counterexample given by Xia and Gao for one result obtained by Krener and Respondek is not a real counterexample. For this purpose, they consider the case where the difference between any two observability indices is not larger than 1. Moreover, they allow a diffeomorphism on the outputs in the obtained non‐linear observer canonical form.
Fault detection based on higher‐order sliding mode observer for a class of switched linear systems
Authors: Van Gorp Jeremy , Defoort Michael , Djemai Mohamed , Veluvolu Kalyana Chakravarthy
Published: August 2015

This study considers the fault detection problem for a class of switched linear systems when the observer matching condition is not satisfied. Without using decoupling transformations, a residual signal, based on reduced order sliding mode observers, is introduced for the detection of faults which occur on the continuous part of the system. Two numerical simulations on the cascade multicellular converter and on the boost converter illustrate the effectiveness of the proposed fault detection scheme.
Event‐triggered distributed ℋ∞ state estimation with packet dropouts through sensor networks
Authors: Ding Derui , Wang Zidong , Shen Bo , Dong Hongli
Published: August 2015

This study is concerned with the event‐triggered distributed ℋ∞ state estimation problem for a class of discrete‐time stochastic non‐linear systems with packet dropouts in a sensor network. An event‐triggered communication mechanism is adopted over the sensor network with hope to reduce the communication burden and the energy consumption, where the measurements on each sensor are transmitted only when a certain triggering condition is violated. Furthermore, a novel distributed state estimator is designed where the available innovations are not only from the individual sensor, but also from its neighbouring ones according to the given topology. The purpose of the problem under consideration is to design a set of distributed state estimators such that the dynamics of estimation errors is exponentially mean‐square stable and also the prespecified ℋ∞ disturbance rejection attenuation level is guaranteed. By utilising the property of the Kronecker product and the stochastic analysis approaches, sufficient conditions are established under which the addressed state estimation problem is recast as a convex optimisation one that can be easily solved via available software packages. Finally, a simulation example is utilised to illustrate the usefulness of the proposed design scheme of event‐triggered distributed state estimators.
H∞ control for a class of multi‐agent systems via a stochastic sampled‐data method
Authors: Wei Guoliang , Wang Licheng , Liu Yurong
Published: August 2015

In this study, the stochastic sampled‐data approach is developed to deal with the H∞ control problem for a class of linear multi‐agent systems. For each agent, signals should be transmitted to the control input, including not only its own measurements, but also the output information received from the neighbour agents. The relationships of information communications between the whole multi‐agents are totally reflected by a weighted directed graph with a fixed topology structure. To the addressed problem, the author's focus is to design an output feedback controller for each agent such that, for the external energy bounded disturbances, the exponential stability in the mean square sense and interference rejection ability under consideration can be guaranteed. By assuming that the sampling period of each agent switches between two values in a probabilistic way, the stochastic sampling phenomenon is well characterised in every sampling tasks. In virtue of Lyapunov theory and semi‐definite programming method, sufficient conditions are derived to ensure the exponential stability as well as H∞ performance, and the feedback controllers are also designed by solving some certain matrix inequalities. Finally, a numerical simulation is given to demonstrate the validness of the proposed control strategy.
Robust stabilisation of uncertain time‐delay dynamical systems with unknown bounds of uncertainties: a non‐linear control method
Authors: Wu Hansheng
Published: August 2015

In this study, the problem of robust stabilisation is considered for a class of uncertain dynamical systems with state delays. Here, it is assumed that the upper bounds of the delayed state perturbations, uncertainties and external disturbances are completely unknown. For such a class of uncertain time‐delay dynamical systems, a novel design method is presented in which a class of continuous memoryless robust stabilising controllers is constructed. In particular, by making use of the presented method, it is not required to introduce some adaptive schemes to update the unknown upper bounds, which makes the control schemes simpler than adaptive robust control schemes reported in the control literature. Moreover, such a control scheme proposed in this study will be called adaptation‐free robust control scheme. It is also shown that the solutions of the resulting closed‐loop time‐delay dynamical systems can be guaranteed to be uniformly ultimately bounded. Finally, the simulations of some numerical examples are provided to demonstrate the validity of the theoretical results.
Robust finite‐time bounded control for discrete‐time stochastic systems with communication constraint
Authors: Song Jun , Niu Yugang , Zou Yuanyuan
Published: August 2015

This study is concerned with the problem of finite‐time stochastic bounded (FTSB) control for discrete‐time stochastic system with communication constraint, in which there may exist external bounded disturbance and state‐dependent noise. In particular, the state of system may loss when transmitted via communication networks. In this study, a compensating strategy is employed to cope with the packet dropout. Moreover, the concepts on FTSB are introduced and relevant issues are discussed. By constructing suitable Lyapunov–Krasovskii functional, sufficient conditions dependent on both dropout probability and specified work time are derived to ensure the FTSB of the closed‐loop system. Meanwhile, a prescribed H∞ performance is also achieved. Finally, an F‐18 aircraft model is employed to illustrate the proposed approach.
Event‐based state estimation for stochastic hybrid systems
Authors: Lee Sangjin , Hwang Inseok
Published: August 2015

This study presents a state estimation algorithm for the stochastic hybrid system with event‐based sampling. In event‐based sampling, sensors transmit their measurements to an estimator only when predefined events happen, to reduce the communication cost. On the basis of the event‐based sampling, the hybrid state estimation problem is formulated as to compute the probability density of the hybrid state with the sequence of noisy measurements generated at certain events. This hybrid state estimation problem is challenging since it requires computation of the exponentially increasing number of probabilities of the discrete state histories and evaluation of the multivariate integration. The proposed event‐based hybrid state estimation algorithm utilises the interacting multiple model approach and pseudo measurement generation method to overcome these difficulties. The algorithm is then demonstrated with an illustrative aircraft tracking example.
Stabilisation control for planar bilinear systems by using switching law to minimise return ratio
Authors: Cong Shen , Chen Jiaqi
Published: August 2015

By using piecewise constant control, the authors embed planar bilinear system into switching control model. On the basis of interpreting switching stabilisation mechanism in terms of return ratio, they develop a systematic approach to solve the piecewise constant control from the switching law that minimises return ratio. The existence and construction of stabilisation control in a strong way rely on an invariant that characterises the interrelation of the system matrices.
Quality‐by‐design by skewed spherical structured singular value
Authors: Kishida Masako , Braatz Richard D.
Published: August 2015

This study develops numerical algorithms to compute an ellipsoidal set of input parameters, called a design space, that ensures that the system outputs lie within a set of design specifications in quality‐by‐design. The algorithm is based on a proposed skewed spherical structured singular value νs, for which this study derives upper bounds and proves the (scaled) main loop theorems and small‐gain theorem for the Frobenius norm. Three examples are included to illustrate applications of the numerical algorithms.
Integral‐based event‐triggered control scheme for a general class of non‐linear systems
Authors: Mousavi Seyed Hossein , Ghodrat Mohsen , Marquez Horacio J.
Published: August 2015

In this study, an integral‐based event‐driven mechanism is proposed for a general class of non‐linear systems. The proposed scheme is less conservative than earlier work on the subject and achieves asymptotic stability without forcing the derivative of the Lyapunov function to be negative between samples. A rigorous proof is given, showing that the proposed triggering condition is more effective than the corresponding traditional approaches. Simulation results are provided to illustrate the effectiveness of the proposed solution.
Data‐driven consensus control for networked agents: an iterative learning control‐motivated approach
Authors: Meng Deyuan , Du Wen , Jia Yingmin
Published: August 2015

This study considers an iterative learning control approach to achieve accurate coordination performances of the output data sequences for multiple plants that are involved in a networked environment. To realise such a desirable control objective, an update process of the input data sequence is needed to refine its output performance iteratively for each plant, which uses the local or nearest neighbour knowledge. The nominal multi‐agent systems are employed as the plants’ description, for which input–output data‐driven consensus problems are addressed in a hybrid networked environment given by signed directed graphs with both cooperative and antagonistic interactions. It is proved that the output data can be guaranteed to achieve bipartite consensus or remain stable for the multi‐agent networks under structurally balanced or structurally unbalanced signed graphs. Moreover, the convergence conditions are derived, which need less knowledge of the agents’ plant, and the proposed consensus results can be developed to take into account the plant uncertainties and noises. Simulation tests are performed to verify the effectiveness of the learning approach in refining high input–output data‐driven consensus performances of networked agents.
Robust finite‐time stability and stabilisation for switched linear parameter‐varying systems and its application to bank‐to‐turn missiles
Authors: Liu Yifan , Yang Jianying , Li Chunzhi
Published: August 2015

Finite‐time stability analysis and controller synthesis for switched linear parameter‐varying (LPV) systems are discussed in this paper. A new finite‐time stability condition and robust finite‐time controller design method are presented for switched LPV systems with two different structured uncertainty modelling assumptions (i.e. affine linear structured uncertainty or polytopic structured uncertainty). On the one hand, by using the piecewise parameter‐dependent Lyapunov‐like function, a less conservativeness finite‐time stability condition is established. On the other hand, the new condition based on linear matrix inequalities relieves the controller design burden of dealing with specific applications. Finally, the provided design method is highly desirable to treat the problem of attitude control of bank‐to‐turn missiles with different channels coupling, and computer simulations demonstrate the effectiveness and superiority of the theoretical results.
Robust H∞ control for time‐delay networked control systems with probability constraints
Authors: Wang Shuo , Yu Mei , Sun Ximing
Published: August 2015

In this study, the probability‐guaranteed H∞ control of networked control systems (NCSs) with time‐varying networked‐induced delays is addressed. The time‐varying delays are modelled as polytopic uncertainty by a new approximation method based on real Jordan form. The system uncertainty lies in a parameter hyper‐rectangle box which can shrink, i.e. the probability can be less than one with a better disturbance attenuation level. By the uniformity principle and the one‐to‐one correspondence between the time delays and the vertices of polytopic system, a sufficient condition for the NCS to achieve prescribed performance with a given probability is derived. The controller synthesis problem is also proposed to meet the probabilistic requirement by solving a set of bilinear matrix inequalities iteratively. A uniform distribution is assumed for all the delays and thus the maximal probability guaranteeing the given performance can be calculated.
Coordination control design for formation reconfiguration of multiple spacecraft
Authors: Zhou Ning , Xia Yuanqing
Published: August 2015

This study investigates the high precision control design of formation reconfiguration for a group of spacecraft with obstacle/collision avoidance and unknown disturbances. First, by utilising the null‐space‐based method, a set of pre‐designed velocities are calculated for each spacecraft to perform the tasks with the obstacle/collision avoidance task has a higher priority. Second, a task‐based adaptive non‐singular fast terminal sliding mode coordination control algorithm (TANCCA) is proposed, which can guarantee all the spacecraft to implement the formation reconfiguration while avoiding obstacles/collisions under an unknown disturbed environment. To solve the chattering problem caused by the discontinuity of TANCCA, a modified TANCCA (MTANCCA) is then developed, which is continuous and chattering‐free. Finally, the authors use the solution to the formation reconfiguration control problem for six spacecrafts in a circular Low Earth Orbit at 600 km altitude. The results of the simulation show that the MTANCCA is successful in achieving the obstacle/collision avoidance, disturbance rejection, fast convergence, and high control precision without any collisions or rules broken.
Optimal proportional–integral–derivative set‐point weighting and tuning rules for proportional set‐point weights
Authors: Hast Martin , Hägglund Tore
Published: August 2015

In this study, design of low‐order feedforward controllers from both reference signal and measurable disturbance for proportional–integral–derivative (PID) controllers is considered. The feedforward controllers from reference are equivalent to the use of a PID controller with set‐point weighting. The design problem is formulated as a convex optimisation problem and then solved for a batch of process models. The optimal proportional set‐point weights are then used to derive tuning rules that minimise the integrated absolute error. Examples illustrate the usefulness of the proposed method and tuning rules.
Mixed sliding mode fuzzy control for discrete‐time non‐linear stochastic systems subject to variance and passivity constraints
Authors: Chang Wen‐Jer , Chen Po‐Hsun , Ku Cheung‐Chieh
Published: August 2015

In this study, a novel multi‐objective sliding mode fuzzy control technique is presented for a class of discrete‐time non‐linear stochastic systems that are represented by Takagi–Sugeno (T–S) fuzzy models. Subject to variance and passivity constraints, parallel distributed compensation based sliding mode fuzzy control approach is investigated for the discrete‐time T–S fuzzy models. Combining Lyapunov theory, passivity theory and covariance theory, sufficient conditions are derived to satisfy stability, passivity and variance constraints. The iterative linear matrix inequality algorithm is employed in this study to solve these sufficient conditions. The contribution of this study is to develop a novel sliding mode fuzzy control method such that the closed‐loop discrete‐time non‐linear stochastic system achieves passivity constraint and individual state variance constraints, simultaneously. At last, the simulations of controlling a discrete‐time non‐linear ship steering system are given in a numerical example to demonstrate the effectiveness and usefulness of proposed sliding mode fuzzy control methodology.
Synchronisation analysis of Boolean networks based on equivalence
Authors: Chen Hongwei , Liang Jinling , Liu Yang , Huang Tingwen
Published: August 2015

This study studies the synchronisation of two Boolean networks (BNs) coupled in the drive‐response configuration, and presents a number of new results. A new indicator variable, which plays an important role in characterising the synchronised nodes between the drive BN and the response BN, is defined by coordinate equivalence. Consequently, some necessary and sufficient conditions are derived for the general synchronisation of the drive‐response BNs. Moreover, the upper bound of time to check the criterion is given. Two examples are provided to illustrate the efficiency of the obtained results.
Noise modelling in time‐of‐flight sensors with application to depth noise removal and uncertainty estimation in three‐dimensional measurement
Authors: Belhedi Amira , Bartoli Adrien , Bourgeois Steve , Gay‐Bellile Vincent , Hamrouni Kamel , Sayd Patrick
Published: August 2015

Time‐of‐flight (TOF) sensors provide real‐time depth information at high frame‐rates. One issue with TOF sensors is the usual high level of noise (i.e. the depth measure's repeatability within a static setting). However, until now, TOF sensors’ noise has not been well studied. The authors show that the commonly agreed hypothesis that noise depends only on the amplitude information is not valid in practice. They empirically establish that the noise follows a signal‐dependent Gaussian distribution and varies according to pixel position, depth and integration time. They thus consider all these factors to model noise in two new noise models. Both models are evaluated, compared and used in the two following applications: depth noise removal by depth filtering and uncertainty (repeatability) estimation in three‐dimensional measurement.