bluuebunny/crossref_metadata_2025 huggingface dataset:
Cycloplatinated(ii) complexes bearing 1,1′-bis(diphenylphosphino)ferrocene ligand: biological evaluation and molecular docking studies
Authors: Fereidoonnezhad Masood , Shahsavari Hamid R. , Abedanzadeh Sedigheh , Behchenari Behnoosh , Hossein-Abadi Mojdeh , Faghih Zahra , Beyzavi M. Hassan
Published: December 2017

Cycloplatinated(ii) complexes containing dppf ligand were prepared. These complexes exhibited high cytotoxicity and apoptosis-inducing activities to human cancer cell lines.
Molecular detection by liquid gated Hall effect measurements of graphene
Authors: Zhan Hualin , Cervenka Jiri , Prawer Steven , Garrett David J.
Published: December 2017

A liquid gated Hall effect measurement of graphene shows that the Hall coefficient is more sensitive to the change of l-histidine concentration in the pM range than the sheet resistance.
Multifunctional Cu–Ag2S nanoparticles with high photothermal conversion efficiency for photoacoustic imaging-guided photothermal therapy in vivo
Authors: Dong Lile , Ji Guanming , Liu Yu , Xu Xia , Lei Pengpeng , Du Kaimin , Song Shuyan , Feng Jing , Zhang Hongjie
Published: December 2017

The novel Cu–Ag2S/PVP NPs with high photothermal conversion efficiency could be employed as effective photoacoustic imaging guided photothermal therapy agents.
A comparative study of redox-active, ambipolar electrochromic triphenylamine-based polyimides prepared by electrochemical polymerization and conventional polycondensation methods
Authors: Hsiao Sheng-Huei , Liao Wei-Kai , Liou Guey-Sheng
Published: December 2017

The spectroscopic, electrochemical and electrochromic properties of polyimides with tetraphenylbenzidine (TPB) units prepared by electropolymerization and polycondensation were compared.
Enhanced sulfamethoxazole degradation in soil by immobilized sulfamethoxazole-degrading microbes on bagasse
Authors: Hu Shengbing , Hu Huimin , Li Wenlong , Ke Yaoyi , Li Minghua , Zhao Yuechun
Published: December 2017

The presence of sulfamethoxazole (SMX) in the environment is becoming a serious problem because of its toxicity and high risk to human health and microbial activity.
Nanosilica-supported thiosemicarbazide–glutaraldehyde polymer for selective Au(iii) removal from aqueous solution
Authors: Zhang Gengwei , Zhou Yang , Ding Zhao , Fu Likang , Wang Shixing
Published: December 2017

A thiosemicarbazide/nanosilica composite exhibited significant uptake toward Au(iii). Adsorption isotherms and kinetics revealed a synergistic effect of ionic interaction and chelation exists between Au(iii) and the synthesized nanocomposites.
Sphingolipidomic study of davidiin-treated HepG2 human hepatocellular carcinoma cells using UHPLC-MS
Authors: Xie Li-Min , Yau Lee-Fong , Jiang Zhi-Hong , Zhang Li-Yan , Xia Yun , Wang Jing-Rong
Published: December 2017

An improved sphingolipidomic approach demonstrated elevated dihydroceramide and sphinganine, which may be due to the inhibition effect of davidiin on DES.
Interfacial interaction and enhanced image contrasts in higher mode and bimodal mode atomic force microscopy
Authors: Shi Shuai , Guo Dan , Luo Jianbin
Published: December 2017

The higher and bimodal modes of the first and the third modes gain a clear advantage over traditional modes in image contrast.
Carbazole-based compounds containing aldehyde and cyanoacetic acid: optical properties and applications in photopolymerization
Authors: Abro Hussain Ahmed , Zhou Tengfei , Han Weixiang , Xue Tanlong , Wang Tao
Published: December 2017

Carbazole-based aldehyde and cyanoacetic acid containing dyes were synthesized and applied as photosensitizers in photopolymerization with a LED light source at 455 nm.
Synchronous magnetic control of water droplets in bulk ferrofluid
Authors: Katsikis Georgios , Breant Alexandre , Rinberg Anatoly , Prakash Manu
Published: December 2017

Synchronous magnetic 2D control of water droplets in bulk ferrofluid including generation, propagation, droplet break-up and droplet interactions.
Coordination-driven micellelization of block copolymers with gold(i) complexes induces remarkable phosphorescence enhancements with reversible mechanochromism
Authors: Wang Jun , He Qun , Wang Chen , Bu Weifeng
Published: December 2017

The coordination-driven self-assembly of block copolymers with gold(i) complexes yields spherical micelles with remarkable phosphorescence enhancements. One of the gold(i)-containing metallopolymers shows reversible mechanochromic luminescence.
Biomineralization-mimetic preparation of hybrid membranes with ultra-high loading of pristine metal–organic frameworks grown on silk nanofibers for hazard collection in water
Authors: Li Zhishang , Zhou Guanshan , Dai Huang , Yang Mingying , Fu Yingchun , Ying Yibin , Li Yanbin
Published: December 2017

The efficient incorporation of porous materials into membranes to prepare hybrid membranes for the development of a separation device for water pollution treatment is described.
An advanced elastomer with an unprecedented combination of excellent mechanical properties and high self-healing capability
Authors: Liu Jie , Liu Jun , Wang Sheng , Huang Jing , Wu Siwu , Tang Zhenghai , Guo Baochun , Zhang Liqun
Published: December 2017

An advanced elastomer was developed by incorporating a dual-dynamic network into cis-polyisoprene, which combines excellent mechanical properties with high self-healing capability.
Influence of water intercalation and hydration on chemical decomposition and ion transport in methylammonium lead halide perovskites
Authors: Jong Un-Gi , Yu Chol-Jun , Ri Gum-Chol , McMahon Andrew P. , Harrison Nicholas M. , Barnes Piers R. F. , Walsh Aron
Published: December 2017

The application of methylammonium (MA) lead halide perovskites, CH3NH3PbX3 (X = I, Br, Cl), in perovskite solar cells has made great recent progress in performance efficiency during recent years.
Super-compatible functional boron nitride nanosheets/polymer films with excellent mechanical properties and ultra-high thermal conductivity for thermal management
Authors: Wang Jiemin , Wu Yuanpeng , Xue Ye , Liu Dan , Wang Xuebin , Hu Xiao , Bando Yoshio , Lei Weiwei
Published: December 2017

Super compatible functional boron nitride (FBN) nanosheets and polyvinyl alcohol (PVA) composite films are well fabricated by facile aqueous vacuum filtering.
Molecular basis for the integration of environmental signals by FurB from Anabaena sp. PCC 7120
Authors: Sein-Echaluce Violeta C. , Pallarés María Carmen , Lostao Anabel , Yruela Inmaculada , Velázquez-Campoy Adrián , Luisa Peleato M. , Fillat María F.
Published: December 2017

FUR (Ferric uptake regulator) proteins are among the most important families of transcriptional regulators in prokaryotes, often behaving as global regulators. In the cyanobacterium Anabaena PCC 7120, FurB (Zur, Zinc uptake regulator) controls zinc and redox homeostasis through the repression of target genes in a zinc-dependent manner. In vitro, non-specific binding of FurB to DNA elicits protection against oxidative damage and avoids cleavage by deoxyribonuclease I. The present study provides, for the first time, evidence of the influence of redox environment in the interaction of FurB with regulatory zinc and its consequences in FurB–DNA-binding affinity. Calorimetry studies showed that, in addition to one structural Zn(II), FurB is able to bind two additional Zn(II) per monomer and demonstrated the implication of cysteine C93 in regulatory Zn(II) coordination. The interaction of FurB with the second regulatory zinc occurred only under reducing conditions. While non-specific FurB–DNA interaction is Zn(II)-independent, the optimal binding of FurB to target promoters required loading of two regulatory zinc ions. Those results combined with site-directed mutagenesis and gel-shift assays evidenced that the redox state of cysteine C93 conditions the binding of the second regulatory Zn(II) and, in turn, modulates the affinity for a specific DNA target. Furthermore, differential spectroscopy studies showed that cysteine C93 could also be involved in heme coordination by FurB, either as a direct ligand or being located near the binding site. The results indicate that besides controlling zinc homeostasis, FurB could work as a redox-sensing protein probably modifying its zinc and DNA-binding abilities depending upon environmental conditions.
Structural and biochemical characterization of the catalytic domains of GdpP reveals a unified hydrolysis mechanism for the DHH/DHHA1 phosphodiesterase
Authors: Wang Feng , He Qing , Su Kaixuan , Wei Tiandi , Xu Sujuan , Gu Lichuan
Published: December 2017

The Asp-His-His and Asp-His-His-associated (DHH/DHHA1) domain-containing phosphodiesterases (PDEs) that catalyze degradation of cyclic di-adenosine monophosphate (c-di-AMP) could be subdivided into two subfamilies based on the final product [5′-phosphadenylyl-adenosine (5′-pApA) or AMP]. In a previous study, we revealed that Rv2837c, a stand-alone DHH/DHHA1 PDE, employs a 5′-pApA internal flipping mechanism to produce AMPs. However, why the membrane-bound DHH/DHHA1 PDE can only degrade c-di-AMP to 5′-pApA remains obscure. Here, we report the crystal structure of the DHH/DHHA1 domain of GdpP (GdpP-C), and structures in complex with c-di-AMP, cyclic di-guanosine monophosphate (c-di-GMP), and 5′-pApA. Structural analysis reveals that GdpP-C binds nucleotide substrates quite differently from how Rv2837c does in terms of substrate-binding position. Accordingly, the nucleotide-binding site of the DHH/DHHA1 PDEs is organized into three (C, G, and R) subsites. For GdpP-C, in the C and G sites c-di-AMP binds and degrades into 5′-pApA, and its G site determines nucleotide specificity. To further degrade into AMPs, 5′-pApA must slide into the C and R sites for flipping and hydrolysis as in Rv2837c. Subsequent mutagenesis and enzymatic studies of GdpP-C and Rv2837c uncover the complete flipping process and reveal a unified catalytic mechanism for members of both DHH/DHHA1 PDE subfamilies.
The role of gut microbiota in the effects of maternal obesity during pregnancy on offspring metabolism
Authors: Zhou Liyuan , Xiao Xinhua
Published: December 2017

Obesity is considered a global epidemic. Specifically, obesity during pregnancy programs an increased risk of the offspring developing metabolic disorders in addition to the adverse effects on the mother per se. Large numbers of human and animal studies have demonstrated that the gut microbiota plays a pivotal role in obesity and metabolic diseases. Similarly, maternal obesity during pregnancy is associated with alterations in the composition and diversity of the intestine microbial community. Recently, the microbiota in the placenta, amniotic fluid, and meconium in healthy gestations has been investigated, and the results supported the “in utero colonization hypothesis” and challenged the traditional “sterile womb” that has been acknowledged worldwide for more than a century. Thus, the offspring microbiota, which is crucial for the immune and metabolic function and further health in the offspring, might be established prior to birth. As a detrimental intrauterine environment, maternal obesity influences the microbial colonization and increases the risk of metabolic diseases in offspring. This review discusses the role of the microbiota in the impact of maternal obesity during pregnancy on offspring metabolism and further analyzes related probiotic or prebiotic interventions to prevent and treat obesity and metabolic diseases.
False Belief Development in Children Who Are Hard of Hearing Compared With Peers With Normal Hearing
Authors: Walker Elizabeth A. , Ambrose Sophie E. , Oleson Jacob , Moeller Mary Pat
Published: December 2017

Purpose

This study investigates false belief (FB) understanding in children who are hard of hearing (CHH) compared with children with normal hearing (CNH) at ages 5 and 6 years and at 2nd grade. Research with this population has theoretical significance, given that the early auditory–linguistic experiences of CHH are less restricted compared with children who are deaf but not as complete as those of CNH.

Method

Participants included CHH and CNH who had completed FB tasks as part of a larger multicenter, longitudinal study on outcomes of children with mild-to-severe hearing loss. Both cross-sectional and longitudinal data were analyzed.

Results

At age 5 years, CHH demonstrated significant delays in FB understanding relative to CNH. Both hearing status and spoken-language abilities contributed to FB performance in 5-year-olds. A subgroup of CHH showed protracted delays at 6 years, suggesting that some CHH are at risk for longer term delays in FB understanding. By 2nd grade, performance on 1st- and 2nd-order FBs did not differ between CHH and CNH.

Conclusions

Preschool-age CHH are at risk for delays in understanding others' beliefs, which has consequences for their social interactions and pragmatic communication. Research related to FB in children with hearing loss has the potential to inform our understanding of mechanisms that support social–cognitive development, including the roles of language and conversational access.
Conceptual Scoring and Classification Accuracy of Vocabulary Testing in Bilingual Children
Authors: Anaya Jissel B. , Peña Elizabeth D. , Bedore Lisa M.
Published: December 2017

Purpose

This study examined the effects of single-language and conceptual scoring on the vocabulary performance of bilingual children with and without specific language impairment. We assessed classification accuracy across 3 scoring methods.

Method

Participants included Spanish–English bilingual children (
N
= 247) aged 5;1 (years;months) to 11;1 with and without specific language impairment. Children completed the English and bilingual versions of the Expressive One-Word Picture Vocabulary Test–Third Edition (Brownell, 2000a, 2001). Six scores, 2 representing monolingual scores in English and Spanish and 4 conceptual scores, were derived. The conceptual scores included within-test conceptual scores, which credited language responses in the other language during test administration, and across-test conceptual scores, which we compiled by examining responses across independent administrations of the test in each language.

Results

Across-test conceptual scoring resulted in the highest scores and better overall classification, sensitivity, and specificity than within-test conceptual scoring. Both were superior to monolingual scoring; however, none of the methods achieved minimum standards of 80% accuracy in sensitivity and specificity.

Conclusions

Results suggest that bilingual children are not always able to readily access their other language in confrontation naming tasks. Priming or inhibition may play a role in test performance. Across-test conceptual scoring yielded the highest classification accuracy but did not meet minimum standards.
Low profile SIW slot antenna with wide beam‐width radiation pattern
Authors: Liu Chun‐Mei , Xiao Shaoqiu , Zhang Zongtang , Feng Jiaxin
Published: December 2017

A linearly polarised antenna with wide beam‐width is proposed. This antenna is based on substrate integrated waveguide (SIW) cavity. The half‐power beam‐width is about 145° in the E‐plane, and 140° in the H‐plane. This proposed antenna has a low profile of 0.03λ0 (λ0 denotes to the space wavelength corresponding to the operating frequency centre) and a compact size of 0.31λ0 × 0.31λ0, which is very suitable for modern communication systems. The maximum gain is about 6 dBi, and the radiation efficiency is about 90% at the working frequency band. The cross polarisation is very small.
Performance analysis of spectrum sharing‐based multi‐hop decode‐and‐forward over Nakagami‐m fading channels subject to additive white generalised Gaussian noise
Authors: Badarneh Osamah S. , Almehmadi Fares S. , Kadoch Michel
Published: December 2017

In this work, the authors study the performance of decode‐and‐forward cognitive multi‐hop networks in an underlay spectrum sharing strategy for Nakagami‐m fading channels with additive white generalised Gaussian noise. To this end, new exact analytical expressions for the average bit error rate of M‐ary quadrature amplitude modulation (M‐QAM) and M‐ary phase shift keying are derived and evaluated. In addition, an exact expression for the average symbol error rate of M‐QAM is provided. Moreover, lower‐ and upper‐bound expressions for the ergodic capacity are obtained. Different scenarios are presented to study the influence of various key system parameters, such as fading severity, noise shaping parameter, and interference temperature, on the system performance. The obtained analytical results are supported with Monte Carlo simulations to confirm the accuracy of the analytical derivations.
Cluster head selection method for content‐centric mobile social network in 5G
Authors: Tulu Muluneh M. , Hou Ronghui , Li Chuanyin , Amentie Melkamu D.
Published: December 2017

In a social network, spreading information through the powerful leader of the community is highly valuable. Applying effective methods to identify influential nodes will leverage cellular networks in device‐to‐device local communication. In this study, entropy of betweenness centrality (EBC) combining the degree of the node and the degree of the neighbour node is proposed as a metric to select nodes from large and complex networks to disseminate information easily. EBC describes how the node is essential to connect two regions of the network. In the authors' work, nodes are identified by EBC, which is evaluated by susceptible‐infected (SI) model. Hence, if the source of infection in the SI model is one node and the percentage of infected nodes is the largest, which means that the source node is the most powerful node in the network. Simulation results show that the proposed method performs better than the existing methods to spread information in the mobile social network.
Game‐theoretic radio resource management for relay‐assisted access in wireless networks
Authors: Kai Cai Hong , Li Hui , Qian Liping
Published: December 2017

The radio resource management for relay‐assisted access where every terminal user communicates with the base station through relay users is studied. In particular, the problem formulation is to maximise the total utility across relay users and terminal users under the bandwidth constraint of device‐to‐device (D2D) links. To solve such an optimisation problem, the authors first explore the diversity of channels between the relay users and the terminal users based on the maximum weighted bipartite matching theory, and adopt Hungarian algorithm to select the best relay user for each terminal user. Then, to stimulate relay users to participate in the cooperation, they design a two‐stage Stackelberg game to jointly maximise the utilities of the selected relay user and the terminal user. In this doing, every terminal user can obtain the optimal data rate with the aid of relay. Finally, the authors' simulations show that the proposed relay user selection and game‐theoretic resource allocation scheme can effectively improve the downloading rates of terminal users and achieve a ‘win‐win’ strategy between the terminal users and relay users for relay‐assisted access using D2D communications.
Low‐latency and high‐reliability performance analysis of relay systems
Authors: Long Hang , Xiang Wei , Sun Yao
Published: December 2017

The latency and reliability of single‐relay and multi‐relay systems are investigated in this study. In a single‐relay system with the amplify‐and‐forward protocol, a new approximation analytical method is proposed for the outage probability, which can also be extended to be used in the multi‐relay system. The latency‐reliability trade‐off degree (LRTD) of single‐ and multi‐relay systems, i.e. the slope of the latency‐outage probability curve with logarithmic scales, is analysed and proved to be the same as the number of relay nodes. In the multi‐relay system, the relationship between the system LRTD and the channel state information overhead is investigated. The optimum number of relay nodes can be derived according to the approximate expression of the outage probability. A simple iterative method is proposed to obtain the optimum number of relay nodes. The convergence of the iterative method is also proved.
Energy‐efficient radio resource allocation in software‐defined wireless sensor networks
Authors: Zhang Yueyue , Zhu Yaping , Yan Feng , Xia Weiwei , Shen Lianfeng
Published: December 2017

The software‐defined wireless sensor networks (SDWSNs) have been proposed recently to solve the energy limitation of sensor nodes and extend the lifetime of the wireless sensor networks by fast node reconstruction and dynamical resource allocation. In this study, the authors investigate an energy‐efficient resource allocation algorithm in SDWSNs, in which radio resource allocation could be handled at central controllers with powerful storage and computation capacity. In this algorithm, the authors formulate an optimisation problem to minimise the energy consumption, under the individual constraint of quality of service. Then, the initial optimisation problem is transformed using semidefinite relaxation, to achieve centralised adaptive bandwidth and power allocation (CABPA). Additionally, two special cases are derived to reveal the performance of the CABPA. Furthermore, an OpenFlow‐based scheme is proposed for information exchanging and updating to realise the centralised resource allocation. Meanwhile, a distributed scheme with limited information about the whole network is developed to serve as a performance benchmark for the CABPA in the SDWSN. Finally, the simulation results reveal that the proposed CABPA performs better than the other algorithms, and it balances the power and bandwidth utilisation.
Terahertz band communication using plasma wave propagation in multilayer graphene heterostructures
Authors: Rakheja Shaloo
Published: December 2017

Graphene‐based heterostructures provide a viable platform to implement optoelectronic devices that can operate in the terahertz (THz) band. In this study, the authors focus on multilayer (ML) graphene as the building block to implement high‐frequency and low‐energy plasmonic interconnects for on‐chip signalling in next‐generation systems. Two specific plasmonic interconnect geometries are analysed: single waveguide (SWG) and parallel‐plate waveguide (PPWG). While SWG interconnects support propagating surface plasmons that are polarised in the transverse magnetic direction, in PPWG interconnects, nearly dispersion‐less quasi‐transverse electromagnetic modes are supported. The dispersion characteristics are derived by solving Maxwell's equations in the device setup in which ML graphene presents an impedance boundary condition. The effects of number of layers, electrostatic screening, and Fermi level are included in the model of intra‐band dynamical surface conductivity of ML graphene. The authors also develop analytical models of energy‐per‐bit and bandwidth density for both SWG and PPWG interconnects. The energy dissipation includes the effect of plasmon generation, detection, and modulation circuitry within a thermal‐ and shot‐noise‐limited transmission of information. They quantify optimal interconnect length scales for which plasmonic interconnects provide lower energy and higher bandwidth when compared against their electrical (copper/low‐κ) counterparts at the 2020 ITRS technology node.
Highly miniaturised semi‐loop meandered dual‐band MIMO antenna system
Authors: Jehangir Syed S. , Sharawi Mohammad S. , Shamim Atif
Published: December 2017

A novel dual‐band two‐element directional multiple‐input–multiple‐output (MIMO) antenna system is presented with 68% miniaturisation, which is achieved using a semi‐loop meandered driven element and a small ground plane. The centre frequency of operation is 2 GHz. The antenna system covers two bands: the telemetry L‐band 1.27–1.43 GHz and the global system for mobile communications/long‐term evolution band 1.8–2.133 GHz. The simulation and measurement results are in good agreement. The proposed antenna system mimics the quasi‐Yagi antenna configuration with a measured front‐to‐back ratio of around 15 dB at 1.35 GHz and 17 dB at 2 GHz, which is achieved without using a large ground plane, extra metallic structures, multiple reflector elements, or any complex technique. A gain of more than 5 dBi is measured for the single element with a total radiation efficiency of around 85% in both bands. The measured isolation of the proposed MIMO antenna is more than 15 dB with <0.0785 measured envelope correlation coefficient values in both bands.
Von Neumann stability analysis of the FDTD method applied to non‐magnetised plasma antennas
Authors: Ghaderi Mohammadreza , Moradi Gholamreza
Published: December 2017

The finite difference time domain (FDTD) analysis of plasma antennas, according to the fluid modelling of plasma has matured recently. By coupling other equations such as fluid or Boltzmann momentum relation to Maxwell's equation set, the famous Courant‐Fredrichs‐Lewy stability limit cannot guarantee the convergence of solutions. In plasma cases, explicitly coupling Maxwell's equations with the constitutive equation cause the stability condition to depend on the plasma parameters () in addition to mesh size, and the denser the plasma is, the less stable solutions are. Here, a well‐founded proof to a modified stability condition is presented using linear algebra for both collision‐less and collisional non‐magnetised plasma. Furthermore, the derived values are validated numerically.
Machine learning‐based IDS for software‐defined 5G network
Authors: Li Jiaqi , Zhao Zhifeng , Li Rongpeng
Published: December 2017

As an inevitable trend of future fifth generation (5G) networks, software‐defined architecture has many advantages in providing centralised control and flexible resource management. However, it is also confronted with various security challenges and potential threats with emerging services and technologies. As the focus of network security, intrusion detection systems (IDSs) are usually deployed separately without collaboration. They are also unable to detect novel attacks with limited intelligent abilities, which are hard to meet the needs of software‐defined 5G. In this study, the authors propose an intelligent IDS taking the advances in software‐defined technology and artificial intelligence based on software‐defined 5G architecture. It flexibly integrates security function modules which are adaptively invoked under centralised management and control with a global view. It can also deal with unknown intrusions by using machine learning algorithms. Evaluation results prove that the intelligent IDS achieves better performance with lower overhead. It is also verified that the selected machine learning algorithms show better accuracy and reduced false alarm rate in flow‐based classification.
Research of reactive power control strategy to reduce the reactive power exchange of AC and DC power grid
Authors: Ren‐chuan Tu , Cheng‐gong Zhao , Zhi‐jun Liu , Yong Cui , Wei Xie , De‐sheng Zhou
Published: December 2017

In order to solve the difficulties of steady‐state voltage regulating for ac power grid brought about by surplus reactive power during the small power running for dc project, the general practice is by adding station low reactor or static reactive power compensator to absorb surplus reactive power, or by adjusting the operation mode of ac/dc system to change converter consumption of reactive power, realising the balance of reactive power exchange. Via the detailed analysis and research of auxiliary converter reactive power control strategy (converter and low load reactive power optimisation function) based on different technical route of dc control system, deducing the relation between the converter reactive power consumption and α /γ, current, which show that increasing minimum γ can absorb surplus reactive power, effectively solving ac grid voltage rise during small power running. At the same time, engineering widely used for a low reactor or static reactive power compensator adopted in weak ac system with reactive power balance control strategy are discussed, putting forward the feasible suggestions of reactive power optimisation control strategy to reduce ac/dc power grid reactive power exchange. Experiments proved that the proposed method can effectively solve the surplus reactive power problem during dc low power operation, simplify the converter station reactive power configuration, can be applied in dc project, and has good applicability.
Wind turbine model validation based on state interval and error calculation
Authors: Li Qing , He Jing , Qin Shiyao , Shi Xiaoning
Published: December 2017

In order to simulate and evaluate wind farm low‐voltage ride through capability, wind turbine should be modelled and simulated as real‐life system operation. In this paper, a validation method based on state interval and error calculation is proposed. The model validation specified in domestic and international standards is introduced. The necessity of steady‐ and transient‐state interval definition is analysed through wind turbine transient behaviour research. Meanwhile, allowed tolerances are studied by wind farm simulation and comparison, using wind turbine models with different behaviours. A double‐fed induction generator (DFIG) wind turbine model is validated and the results show that the proposed method with different tolerance in steady‐ and transient‐state intervals is suitable for wind turbine model validation.
Model and control of fuel supply systems of hydrogen/oxygen fuel cell
Authors: Cheng Zhiping , Ren Peng , Xu Ya Li , Zhang Han Nian
Published: December 2017

Fuel supply systems have a great impact on output characteristics and lifetime of the hydrogen/oxygen fuel cell. On the basis of the fuel supply systems of the fuel cell, this study has studied the models of hydrogen supply system and oxygen supply system. Moreover, the fuzzy self‐adaptive proportional–integral–derivative (PID) controllers for hydrogen supply system are designed according to the characteristics of hydrogen and oxygen supply systems. The simulation results show that fuzzy self‐adaptive PID control method can achieve better performance for supply system.
Study on Electromechanical Transient‐Electromagnetic Transient Hybrid Simulation of Photovoltaic Grid‐connected System
Authors: Meng Hang , Liu Wenzhuo , Yang Mingyu , Ye Xiaohui , Song Xinli , Liu Tao
Published: December 2017

Large‐scale photovoltaic (PV) system is one of significant forms of solar energy resources applications, and it is composed of several elements as solar array, boost converter, inverter and load. To further analyse the dynamic response of single‐stage three‐phase PV generation system, especially the detailed simulation of dynamic characteristics of PV cells, DC bus and converter. This study established the electromagnetic transient (EMT) PV station model and conducted a research on EMT–electromechanical transient hybrid simulation. Besides, the PV power plant framework is developed in an independent designed large‐scale power system analysis software package called PSD‐PSModel hybrid simulation platform and the PV grid‐connected system hybrid simulation capabilities are realised. The achievement can contribute to facilitate the cooperation with the PV power station manufactures on the detailed electromagnetic model of actual PV power station and provide a reliable technical support to study the influence on the power system with PV generation integrated.
Cost comparison of AC and DC collector grid for integration of large‐scale PV power plants
Authors: Li Weilin , He Kun , Wang Yaqiang
Published: December 2017

This paper presents a detailed comparison between the traditional ac collector‐grid configuration and dc collector‐grid configuration for large‐scale photovoltaic (PV) power plants. In particular, the cost of these two configurations have been analysed and discussed in detail. A comparison of the total losses in these components helps to identify the configuration that has the potential to operate at higher efficiency and hence generate maximum revenue. The economic viability metrics are calculated and a sensitivity analysis to the most challenging price ratios is presented.
Reactive power optimisation design and fault ride through of MMC‐PLUS
Authors: Yang Zhihan , Xiang Wang , Yao Liangzhong , Wang Zhibing , Wen Jinyu
Published: December 2017

To integrate bulk wind power, a modular multilevel converter (MMC)‐PLUS composed of the series connection of line commutated converter (LCC) and MMC is investigated. The system combines the advantages of LCC and MMC, such as high power, high voltage, self‐commutating and direct current (DC) fault blocking capability. However, due to the coupled control of active power and reactive power, much reactive power should be compensated during the operation of LCC. The study makes a detailed analysis and optimisation of reactive power compensation devices taking into account the PQ operation curve of MMC and making full use of the capacity of MMC. In addition, further studies the control strategy of DC fault isolation and system restart under DC fault. The effectiveness of the reactive power configuration and DC fault strategy is verified by simulations in PSCAD/EMTDC.
Control and operation of a hybrid HVDC integrating wind farm based on SB‐MMC and LCC
Authors: Sun Shida , Xiang Wang , Yao Liangzhong , Li Yan , Wen Jinyu
Published: December 2017

To integrate offshore wind power, a hybrid high‐voltage DC (HVDC) system consisting of the self‐blocking modular multilevel converter (SB‐MMC) and line commutated converter (LCC) is investigated. The SB‐MMC is installed at the sending end to support the wind farm and the LCC is installed at the power grid side. The start‐up strategy of the hybrid system is studied. To eliminate the transients during start‐up, a virtual limiting resistor is introduced for the LCC and a grouping sequentially charging method is proposed for the SB‐MMC. The DC fault behaviour and isolation of the hybrid system is analysed. The response during AC fault and commutation failure at LCC is considered. Finally, the feasibility of start‐up, DC fault isolation and AC fault ride through of the hybrid HVDC system is verified by simulations in power systems computer‐aided design/electro‐magnetic transient design and control.
AC and DC fault ride through hybrid MMC integrating wind power
Authors: Cao Shuai , Xiang Wang , Yao Liangzhong , Yang Bo , Wen Jinyu
Published: December 2017

To transmit bulk wind power over long distance, using high‐voltage direct current (HVDC) transmission technology with overhead lines is a preferred approach. Since direct current (DC) faults are frequent in overhead lines, this study adopts the hybrid modular multilevel converter (MMC) based on half bridge sub‐module and full bridge sub‐module to integrate wind power. The design of controllers, the alternating current (AC) and DC fault ride‐through strategy of the hybrid MMC‐HVDC system will be presented. Since the wind power continues injecting into the system during the faults, the damping resistor is adopted to dissipate the surplus wind power. The coordination control of the damping resistor and the chopper resistor inside the wind turbine is designed. Finally, the performance during AC, DC faults ride though is verified by extensive simulations.
Research on optimal storage capacity of DC micro‐grid system in PV station
Authors: Wu Ming , Sun Li Jing , Zhang Hai , Wang Wei , Luo Guo Min
Published: December 2017

Existing methods to determine the battery bank capacity of micro‐grid composed of photovoltaic (PV) generation and energy storage device are classified and summarised. In the viewpoint of peak load filling and implementing continuous power supply by independent and grid‐connected micro‐grid composed of PV generation and energy storage device, the method for optimal configuration of battery bank capacity is researched. A method of optimising the storage capacity of DC micro‐grids considering the randomness of PV and load is proposed to maximise the local absorption of renewable energy. Based on the K‐means algorithm, the engineering selection basis of PV and storage capacity in DC micro‐grid system is given, and its economic benefit is evaluated. Finally, the efficiency and economy of the energy storage capacity selection method are verified by practical application of 31.5 MW PV power station in Badaling, Beijing.
Adaptation virtual inertia control strategy of DFIG and assessment of equivalent virtual inertia time constant of connected power system
Authors: Tian Xinshou , Wang Weisheng , Chi Yongning , Li Yan , Liu Chao
Published: December 2017

As the mechanical parts of doubly fed induction generator (DFIG) are decoupled from electrical part, the total equivalent rotary inertia of power system are decreased with growing continuously of wind power penetration, which will bring pressure to frequency stability of system. On the basis of analysing operation and control characteristics of DFIG, the equivalent virtual inertia time constant of DFIG, wind farms based on DFIG, and connected power system was calculated. A virtual inertia control strategy of DFIG using rotor current direct control based on equivalent virtual inertia time constant was proposed. The proposed virtual inertia control strategy of DFIG includes traditional control function module, status assessment module, and additional virtual inertia control module. The time domain simulation was carried out on the basis of theoretical analysis, the simulation results show that the proposed virtual inertia control strategy of DFIG can provide efficacious frequency support to the power grid at all kinds of operating conditions, and the frequency stability of power system with large‐scale wind power was improved.
Numerical stability analysis of PMSG‐based wind energy conversion system: a simple example of drive system
Authors: Ye Hua , Tang Yanan , Pei Wei , Kong Li
Published: December 2017

In a permanent magnetic synchronous generator (PMSG)‐based wind energy conversion system (WECS), numerical instability in a simulation environment may occur due to the use of a single integration method. In the WECS, for example, unreasonable numerical oscillations of the drive train with a weak damping may appear. Here, based on the two‐mass shaft model of the drive train, numerical effect of using the weight‐averaged integration method that is used to discretise the differential equation of the drive train is analysed. Through appropriate adjustments of the weighting factor and time‐step size, accurate simulation of the drive train stability can be achieved. Therefore, the consistency of the simulation performance with real WECS behaviour is guaranteed. The obtained numerical oscillatory stability facilitates the studies of the dynamics of a complete PMSG‐based WECS. A small size wind farm is employed to present efficient results by suppressing numerical oscillations on the drive train.
Transient reactive power characteristics of HVDC during commutation failure and impact of HVDC control parameters
Authors: Tu Jingzhe , Pan Yan , Zhang Jian , Zeng Bing , Jia Junchuan , Yi Jun
Published: December 2017

HVDC commutation failure and recovery, the reactive power exchanged between HVDC and AC systems will change largely, showing the external characteristic of ‘large capacity reactive impact load’, so it is quite necessary to carry out studies on this problem. In this study, first, the HVDC sending‐side and receiving‐side reactive power equations in steady state and transient process are given. Second, the HVDC sending‐side and receiving‐side reactive power characteristics during commutation failure and recovery are analysed. Finally, the impact of the HVDC control system parameters is studied. All the contents are verified by simulation of the HVDC equivalent case system.
Modelling and simulation of the photovoltaic power station considering the LVRT and HVRT
Authors: Fan Shichao , Chao Pupu , Zhang Feifei
Published: December 2017

With the increasing capacity of the photovoltaic (PV) power station, the flexibility and security of power grid face significant challenges. It is necessary for the PV power station to have the capability of voltage ride through (VRT). Based on the newest technical rule (Q/GDW 1617‐2015), the control strategies of the low VRT (LVRT) and the high VRT (HVRT) are investigated and improved here by fitting and analysing of the field test data of the PV plant. The improved LVRT control strategy is able to accurately simulate the active power ramp recovery process of the field test data and is able to provide the dynamic voltage support by the reactive power control. The proposed HVRT control strategy makes the PV power station absorb a certain amount of reactive power to restrict the voltage within specific ranges required by the HVRT grid codes. By comparing with the requirements of the technical rule for connecting PV power station to power grid (Q/GDW 1617‐2015) and the simulation results conducted on Matlab/Simulink platform, the proposed LVRT and HVRT control strategies are validated.
Research on technical scheme of outdoor‐layout relay protection in smart substation
Authors: Shuang Song , Xingjin Qiao , Qiangsheng Bu , Yi Yang , Liangliang Song
Published: December 2017

The scheme of secondary equipment outdoor layout in smart substation has become the development trend in constructing smart substation. In this study, some schemes about outdoor layout relay protection in smart substation using electronic transformer are provided and compared, which is mainly focused on technical ideas, implementation plan and their advantages and disadvantages in engineering application. In addition, aiming at the problem of changing in testing, operation and maintenance work under this new mode, the authors provide a brief introduction on assembly line automatically closed‐loop test technology of outdoor layout, miniaturisation relay protection equipment. The research results have been initially applied in design, test, operation and maintenance work in smart substation.
Wind power fluctuation mitigation based low‐frequency oscillation
Authors: Sun Yushu , Ye Hua , Sun Xiaozhe , Miao Fufeng
Published: December 2017

Owing to the stochastic and intermittent of output power of wind farms, the large‐scale grid‐connected wind power could have a remarkable impact on the power system operation. In this study, wind power fluctuation (WPF) mitigation is achieved from the perspective of power system low‐frequency oscillation (LFO). Firstly, in order to meet fluctuation mitigation requirement, model predictive control algorithm is applied to smooth WPF. Secondly, the Hilbert–Huang transform method is used to obtain the influences of wind power before and after smoothing on system LFO. In addition, wind power is decomposed into high, medium and low bands by empirical mode decomposition, and then the impacts of different bands wind power on system LFO are studied. Finally, the influences of wind power with different fluctuation rates on system LFO are analysed based on the WSCC 3‐machine 9‐bus power system, which provides a theoretical reference for smoothing WPF.
Solution of wind turbine blade Doppler and its characteristic analysis
Authors: Tang Bo , Zou Fang , Sun Ziang , Huang Hansheng , Ye Li
Published: December 2017

The Doppler effect caused by the dynamic rotation of the wind turbine blades is an important evidence for the identification of the wind farm clutter at the nearby radar stations. Due to the difficulty in obtaining the accurate radar echo signal of wind turbine blades by the existing methods, the accurate Doppler spectrum cannot be obtained. For that reason, the problem of accurate simulation of radar echo for wind turbine blades is avoided, and a new idea is proposed to solve the Doppler spectrum by using the dynamic radar cross section (RCS) of the blade through the study of the mechanism of the Doppler effect. Based on the matured dynamic RCS exact solution techniques of electrically large size targets, the time‐domain RCS curve of blades in the dynamic motion state is obtained with the quasi‐static method, using the hybrid algorithm of physical optics (PO) method and of equivalent currents method. Based on this method, calculation and analysis of the wind turbine blades' Doppler characteristics in the rotation, torque conditions provide a reference for the recognition of radar target signal of the wind turbine, the reduction of RCS, and wind farm clutter suppression of the nearby radars.
Unbalanced steady‐state model of synchronous machine for EMT initialisation
Authors: Ju Yuntao
Published: December 2017

Unbalanced load flow solution provides the initialisation of electromagnetic transient (EMT) simulation model for the unbalanced active distribution network. The most electro‐magnetic transient program (EMTP) software use the d –q ‐axis‐based synchronous machine's parameters, so the existed sequence component‐based model is not suitable for the EMT model initialisation. In this study, an unbalanced steady‐state synchronous machine model is presented which is derived from the original dynamic model and its parameters are consistent with EMT dynamic model. It is more precise than the sequence component parameters based model. Furthermore, the saturation phenomenon of main flux is also considered in this model. The proposed model is validated and compared with Modelica simulation results.
Early phases in the stellar and substellar formation and evolution
Authors: Barrado D. , de Gregorio Monsalvo I. , Huélamo N. , Morales-Calderón M. , Bayo A. , Palau A. , Ruiz M. T. , Rivière-Marichalar P. , Bouy H. , Morata Ó. , Stauffer J. R. , Eiroa C. , Noriega-Crespo A.
Published: December 2017

Aims. The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs.

Methods. We have conducted deep observations at 870 μm obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information.

Results. We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70 μm, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects.

Conclusions. Our findings provide additional evidence concerning the BD formation mechanism, which seems to be a downsized version of the stellar formation.