bluuebunny/crossref_metadata_2025 huggingface dataset:
Modified cell-permeable JNK inhibitors efficiently prevents islet apoptosis and improves the outcome of islet transplantation
Authors: Noguchi Hirofumi , Miyagi-Shiohira Chika , Nakashima Yoshiki , Ebi Nana , Hamada Eri , Tamaki Yoshihito , Kuwae Kazuho , Kobayashi Naoya , Saitoh Issei , Watanabe Masami
Published: July 2018

We previously reported that treatment with a JNK inhibitory peptide (11R-JNKI) prevents islet apoptosis and enhances the islet function in vivo. In the present study, we explored more efficient JNK inhibitors. The inhibition of the JNK activity by five types of deletion peptides in 11R-JNKI was investigated. One of the peptides, 8R-sJNKI(-9), significantly prevented JNK activation. At a concentration of 1 µM, 8R-sJNKI(-9) inhibited JNK activity similarly to 10 µM 11R-JNKI and the inhibition of the JNK activity by 10 µM 8R-sJNKI(-9) was significantly greater than that by 10 µM 11R-JNK. To evaluate the effects of 8R-sJNKI(-9), porcine islets were cultured with 1 µM of 8R-sJNKI(-9) or 8R-mutant sJNKI(-9) (8R-mJNKI(-9)). After 1 day of culture, the numbers of islets in the 8R-sJNKI(-9)-treated group was significantly higher than that in the 8R-mJNKI(-9)-treated group. After islet transplantation, the blood glucose levels reached the normoglycemic range in 58.3% of streptozotocin-induced diabetic mice in the 8R-sJNKI(-9) group and 0% of the mice in the 8R-mJNKI(-9)-treated group. These data suggest that 8R-sJNKI(-9) inhibits islet apoptosis and improves islet function.
High-quality thulium iron garnet films with tunable perpendicular magnetic anisotropy by off-axis sputtering – correlation between magnetic properties and film strain
Authors: Wu C. N. , Tseng C. C. , Fanchiang Y. T. , Cheng C. K. , Lin K. Y. , Yeh S. L. , Yang S. R. , Wu C. T. , Liu T. , Wu M. , Hong M. , Kwo J.
Published: July 2018

Thulium iron garnet (TmIG) films with perpendicular magnetic anisotropy (PMA) were grown on gadolinium gallium garnet (GGG) (111) substrates by off-axis sputtering. High-resolution synchrotron radiation X-ray diffraction studies and spherical aberration-corrected scanning transmission electron microscope (Cs-corrected STEM) images showed the excellent crystallinity of the films and their sharp interface with GGG. Damping constant of TmIG thin film was determined to be 0.0133 by frequency-dependent ferromagnetic resonance (FMR) measurements. The saturation magnetization (Ms) and the coercive field (Hc) were obtained systematically as a function of the longitudinal distance (L) between the sputtering target and the substrate. A 170% enhancement of PMA field (H⊥) was achieved by tuning the film composition to increase the tensile strain. Moreover, current-induced magnetization switching on a Pt/TmIG structure was demonstrated with an ultra-low critical current density (jc) of 2.5 × 106 A/cm2, an order of magnitude smaller than the previously reported value. We were able to tune Ms, Hc and H⊥ to obtain an ultra-low jc of switching the magnetization, showing the great potential of sputtered TmIG films for spintronics.
One-step synthesis of 1,6-hexanediamine modified magnetic chitosan microspheres for fast and efficient removal of toxic hexavalent chromium
Authors: Yue Rui , Chen Qiumeng , Li Siqi , Zhang Xiaodan , Huang Yuming , Feng Ping
Published: July 2018

Here, we reported a novel one-step hydrothermal route for the facile synthesis of 1,6-hexanediamine functionalized magnetic chitosan microspheres (AF-MCTS), which were characterized by TEM, FT-IR and XPS to look into its morphology, surface functional groups, and adsorption mechanism of Cr(VI) from the aqueous solution. Cr(VI) adsorption on AF-MCTS as a function of contact time, Cr(VI) concentration, pH, and ionic strength was investigated. The adsorption process follows the Langmuir isotherm model and pseudo-second-order kinetic model. The AF-MCTS exhibited high performance for Cr(VI) removal with very fast adsorption rate (reaching equilibrium within 5 min) and high adsorption capacity (208.33 mg/g), which was 1.1 to 12 times that of other chitosan-based adsorbents. Cr(VI) adsorption onto AF-MCTS was an endothermic and spontaneous process. The recovery and reuse of AF-MCTS was demonstrated 11 times without obvious decrease in adsorption capacity. Mechanism study suggested that –OH rather than –NH2groups in AF-MCTS were the electron donors for reducing Cr(VI) to Cr3+. Consumption or addition of H+could trigger the reversible supramolecular coordination between Cr3+and chitosan. Given the easy preparation, low cost, and remarkable performance, AF-MCTS composite is expected to show promising potential for the practical application in removing toxic Cr(VI) from aqueous media.
Topolectrical Circuits
Authors: Lee Ching Hua , Imhof Stefan , Berger Christian , Bayer Florian , Brehm Johannes , Molenkamp Laurens W. , Kiessling Tobias , Thomale Ronny
Published: July 2018

Invented by Alessandro Volta and Félix Savary in the early 19th century, circuits consisting of resistor, inductor and capacitor (RLC) components are omnipresent in modern technology. The behavior of an RLC circuit is governed by its circuit Laplacian, which is analogous to the Hamiltonian describing the energetics of a physical system. Here we show that topological insulating and semimetallic states can be realized in a periodic RLC circuit. Topological boundary resonances (TBRs) appear in the impedance read-out of a topolectrical circuit, providing a robust signal for the presence of topological admittance bands. For experimental illustration, we build the Su-Schrieffer–Heeger circuit, where our impedance measurement detects the TBR midgap state. Topolectrical circuits establish a bridge between electrical engineering and topological states of matter, where the accessibility, scalability, and operability of electronics synergizes with the intricate boundary properties of topological phases.
39 years of directional wave recorded data and relative problems, climatological implications and use
Authors: Pomaro Angela , Cavaleri Luigi , Papa Alvise , Lionello Piero
Published: July 2018

The dataset consists of 39 years of directional wave time series recorded since 1979 at the CNR-ISMAR “Acqua Alta” oceanographic research tower, located in the Northern Adriatic Sea. The extent of the time series allows us to describe the wave climate in the North Adriatic region and to identify trends and links with large scale climate patterns obtained from a single and permanent observational source. The northern part of the Adriatic Sea is characterized by two main wind and correspondingly wave regimes, strongly forced by the regional orography. The high sensitivity of this particular area to even small variations of large scale meteorological patterns allows to explore possible links of the local wave, hence wind, activity with large-scale north hemisphere circulation or weather regimes. Different wave gauges have been used since the start of the measurements, progressively upgraded and repositioned during maintenance operations. The recorded wave data have been thoroughly verified and corrected where necessary.
Sequence-specific 5mC detection in live cells based on the TALE-split luciferase complementation system
Authors: Tsuji Shogo , Shinoda Kouki , Futaki Shiroh , Imanishi Miki
Published: July 2018

The newly developed TALE-split luciferase complementation system enabled sequence-specific 5mC detection of genomic DNA in live cells.
Aggregation enhanced excimer emission (AEEE) of benzo[ghi]perylene and coronene: multimode probes for facile monitoring and direct visualization of micelle transition
Authors: Hussain Ejaz , Niu Niu , Zhou Huipeng , Shahzad Sohail Anjum , Yu Cong
Published: July 2018

Excimer to monomer transition of multimode probes facilitating the accurate monitoring and direct visualization of monomer–micelle transition.
Algorithm for optimal denoising of Raman spectra
Authors: Barton Sinead J. , Ward Tomas E. , Hennelly Bryan M.
Published: July 2018

The algorithm enhances Savitzky–Golay smoothing with maximum likelihood estimation, which outperforms traditional smoothing in terms of peak fidelity and SNR.
Quantification of estrogens in infant formulas by isotope dilution liquid chromatography-tandem mass spectrometry
Authors: Liu Shuan , Li Xiaomin , Zhao Yingchen , Yin Xiong , Zhang Qinghe , Li Xiuqin , Tang Guangshi , Li Hongmei
Published: July 2018

Isotope dilution liquid chromatography-tandem mass spectrometry without any derivatization step was developed to screen estrogens in real infant formula samples.
Electronic modulation of carbon-encapsulated NiSe composites via Fe doping for synergistic oxygen evolution
Authors: Xu Bo , Chen Zhiming , Yang Xiaodong , Wang Xiaomei , Huang Yucheng , Li Cuncheng
Published: July 2018

Carbon-encapsulated Fe-doped NiSe was easily synthesized as an efficient OER catalyst.
Fe3+chelating quinoline–hydrazone hybrids with proven cytotoxicity, leishmanicidal, and trypanocidal activities
Authors: Coa Juan Carlos , Cardona-Galeano Wilson , Restrepo Albeiro
Published: July 2018

Neglected tropical diseases cause great concern in developing countries where there are millions of reported infected humans. Our calculations support a direct relationship between biological activity and the Fe3+chelating ability of the shown set of quinoline–hydrazone hybrids.
Catalytic function of VOx/Al2O3for oxidative dehydrogenation of propane: support microstructure-dependent mass transfer and diffusion
Authors: Luo Qun-Xing , Zhang Xiao-Kang , Hou Bo-Li , Chen Jian-Gang , Zhu Chao , Liu Zhong-Wen , Liu Zhao-Tie , Lu Jian
Published: July 2018

The intrinsic effect of the support microstructure on the catalytic function of VOx/Al2O3in the oxidative dehydrogenation of propane (ODHP) was studied.
Multimodal Prussian blue analogs as contrast agents for X-ray computed tomography
Authors: Promdet Premrudee , Rodríguez-García Bárbara , Henry Alexandria , Nguyen Cathie , Khuu Thien , Galan-Mascaros Jose-Ramon , Sorasaenee Karn
Published: July 2018

Heavy alkaline cation uptake converts Prussian blue analogs (PBAs) into competitive contrast agents for X-ray computed tomography.
Highly selective and sensitive chemosensor based on 2,3-diaminophenazine hydrochloride for the detection of cyanide in pure water and its application in plant seed samples
Authors: Yong Bi-Rong , Wei Tai-Bao , Qu Wen-Juan , Lin Qi , Zhang You-Ming , Yao Hong
Published: July 2018

A 2,3-diaminophenazine hydrochloride (Q1) shows a ultrasensitive visible and fluorescence response for cyanide in pure water via hydrogen bonding.
The construction of an electrochemical sensing interface based on nano-CeO2 cubes for highly sensitive detection of bisphenol A
Authors: Dang Yuan , Cui Rongrong , Wang Xiaojiao , Zhou Yuanzhen
Published: July 2018

A highly sensitive electrochemical sensor for BPA was established based on the CeO2 nanocubes with abundant oxygen vacancies in lattice.
Effects of methyl groups in a pyrimidine-based flexible ligand on the formation of silver(i) coordination networks
Authors: Marchetti Fabio , Pettinari Riccardo , Di Nicola Corrado , Pettinari Claudio , Paul Anup , Crispini Alessandra , Giorno Eugenia , Lelj Francesco , Stoia Sonia , Amati Mario
Published: July 2018

A methyl substituted pyrimidine-based ligand affords coordination polymers with almost linearly coordinated Ag(i) ions regardless of the silver(i) salt used.
Designed formation of Co3O4/ZnCo2O4/CuO hollow polyhedral nanocages derived from zeolitic imidazolate framework-67 for high-performance supercapacitors
Authors: Zhou Saisai , Ye Zhaochun , Hu Sizhong , Hao Chen , Wang Xiaohong , Huang Chengxiang , Wu Fangsheng
Published: July 2018

The construction of Co3O4/ZnCo2O4/CuO hollow polyhedron nanocages derived from zeolitic imidazolate framework-67 for high performance supercapacitors is reported.
MOF-derived sponge-like hierarchical porous carbon for flexible all-solid-state supercapacitors
Authors: Cao Xiao-Man , Sun Zhi-Jia , Zhao Si-Yu , Wang Bing , Han Zheng-Bo
Published: July 2018

Novel 3D sponge-like hierarchical porous carbons using different-sized MOFs (Zn(tbip)) as precursors are successfully prepared via a one-step pyrolysis process, and are promising for application in high-performance flexible all-solid-state supercapacitors.
Reaction of silylallenes with triplet molecular oxygen
Authors: Xia Yuanzhi , Lee Nam-Kyu , Sabbasani Venkata R. , Gupta Saswata , Lee Daesung
Published: July 2018

A facile formal ene reaction of trisubstituted silylallenes with triplet molecular oxygen involving the cleavage of a C(sp2)–H bond has been described.
Bright insights into palladium-triggered local chemotherapy
Authors: Bray Thomas L. , Salji Mark , Brombin Alessandro , Pérez-López Ana M. , Rubio-Ruiz Belén , Galbraith Laura C. A. , Patton E. Elizabeth , Leung Hing Y. , Unciti-Broceta Asier
Published: July 2018

We report fundamental insights into the validity, reliability and clinical feasibility of using heterogeneous Pd catalysts as implantable devices to accurately activate chemotherapy within a tumour.
Bis-pyrene probes of foldamer conformation in solution and in phospholipid bilayers
Authors: Lister Francis G. A. , Eccles Natasha , Pike Sarah J. , Brown Robert A. , Whitehead George F. S. , Raftery James , Webb Simon J. , Clayden Jonathan
Published: July 2018

An optimized fluorescent probe, developed using spectroscopic and crystallographic analysis, reported on peptide foldamer conformation in different environments and revealed that phospholipid chirality can influence conformation.
Machine intelligence decrypts β-lapachone as an allosteric 5-lipoxygenase inhibitor
Authors: Rodrigues Tiago , Werner Markus , Roth Jakob , da Cruz Eduardo H. G. , Marques Marta C. , Akkapeddi Padma , Lobo Susana A. , Koeberle Andreas , Corzana Francisco , da Silva Júnior Eufrânio N. , Werz Oliver , Bernardes Gonçalo J. L.
Published: July 2018

Using machine learning, targets were identified for β-lapachone.
Supercooling of functional alkyl-π molecular liquids
Authors: Lu Fengniu , Jang Keumhee , Osica Izabela , Hagiwara Keita , Yoshizawa Michito , Ishii Masashi , Chino Yoshiaki , Ohta Kazuchika , Ludwichowska Kinga , Kurzydłowski Krzysztof Jan , Ishihara Shinsuke , Nakanishi Takashi
Published: July 2018

The formation of a metastable supercooled alkyl-π molecular liquid was prohibited by subtle alteration of the molecular structure.
Design and performance analyses of solar arrays towards a metric of energy value
Authors: Boivin Adrian B. , Westgate Timothy M. , Holzman Jonathan F.
Published: July 2018

In this work, the contemporary approach of analyzing and optimizing solar technology according to conversion efficiency is expanded upon to recognize an emerging paradigm for supply and demand of solar power.
Permeability and viscoelastic fracture of a model tumor under interstitial flow
Authors: Tran Quang D. , Marcos Marcos , Gonzalez-Rodriguez David
Published: July 2018

Interstitial flow induces deformation and fracture in a model tumor.
ARGET-ATRP synthesis and swelling response of compositionally varied poly(methacrylic acid-co-N,N-diethylaminoethyl methacrylate) polyampholyte brushes
Authors: Ramirez Rachel , Woodcock Jerimiah , Kilbey S. Michael
Published: July 2018

Local comonomer sequence of random polyampholyte brushes synthesized by ARGET ATRP facilitates ionization and promotes self-neutralization across a wide pH range, including in the presence of an added osmolyte.
Self-doped W–WOx nanocermet multilayer films fabricated by single tungsten target reactive sputtering for selective solar absorption
Authors: Wang Wei , Wen Huaixing , Ling San , Li Zhengtong , Su Jingbu , Wang Chengbing
Published: July 2018

Self-doped W–WOx nanocermet multilayer selective solar absorber coatings have been successfully synthesized using only a single tungsten target by limited reactive sputtering.
Famatinite Cu3SbS4 nanocrystals as hole transporting material for efficient perovskite solar cells
Authors: Zeng Qiang , Di Yunxiang , Huang Chun , Sun Kaiwen , Zhao Yuan , Xie Haipeng , Niu Dongmei , Jiang Liangxing , Hao Xiaojing , Lai Yanqing , Liu Fangyang
Published: July 2018

We have developed inorganic copper antimony sulfide (Cu3SbS4) nanocrystals as a hole transporting material (HTM) for PSCs by a hot-injection and spray-deposition technique.
Electron extraction layer based on diketopyrrolopyrrole/isoindigo to improve the efficiency of inverted perovskite solar cells
Authors: Wang Rui , Qiao Jianhui , He Bizu , Tang Xiaosheng , Wu Fei , Zhu Linna
Published: July 2018

Incorporating DPP/ISO-based interfacial material to improve the performance of inverted PSCs.
Porphyrin-based thick-film bulk-heterojunction solar cells for indoor light harvesting
Authors: Yin Hang , Chen Song , Cheung Sin Hang , Li Ho Wa , Xie Yuemin , Tsang Sai Wing , Zhu Xunjin , So Shu Kong
Published: July 2018

A thick-film (∼200 nm) porphyrin-based P1:PC71BM BHJ solar cell achieves an optimized PCE of 18.2%, under a 300 lux illumination of a 3000 K LED tube.
Power and discrete rate adaptation in BER constrained wireless powered communication networks
Authors: Lei Ming , Zhang Xingjun , Yu Bocheng , Dong Xiaoshe
Published: July 2018

Optimal system throughput is a crucial design issue in wireless powered communication networks. Unlike related literature, this study considers the problem of maximising throughput (MTP) for a practical scenario, in which each user node (UN) selects its own rate from a discrete rate set and controls its transmission power according to its own channel state. The MTP with a bit‐error‐rate constraint is investigated based on two general uplink access methods. The formulation size is exponentially large with respect to the problem input. A novel greedy algorithm based on the column generation method (GA‐CGM) is proposed to solve the problem efficiently. The GA‐CGM decomposes the problem into a master problem and a subproblem. The master problem is solved by the simplex method. The subproblem is solved by a greedy algorithm due to its non‐linearity programming model. The max–min throughput problem (MMTP) is also considered, because of the ‘doubly near‐far’ phenomenon which leads to the unfair throughput among different UNs. Experimental results demonstrate that the proposed solutions are close to the optimal solutions for MTP and MMTP problems. They also show increasing the transmission power of a base station or decreasing the path‐loss exponent improves the throughput performance.
Event‐triggered leader–following consensus of non‐linear multi‐agent systems with switched dynamics
Authors: Zou Wencheng , Xiang Zhengrong
Published: July 2018

This study investigates the leader–following consensus problem for a class of switched non‐linear multi‐agent systems via event‐triggered protocols, where the switching signal of each agent is different. Both centralised and decentralised event‐triggered protocols are proposed for the switched non‐linear multi‐agent systems. The results are then extended to the self‐triggered control cases, respectively. It is proved that the practical leader–following consensus can be achieved by designed protocols. Moreover, the feasibility of the proposed control schemes is further verified by excluding the Zeno behaviour. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.
New computation method for average dwell time of general switched systems and positive switched systems
Authors: Zhang Junfeng , Li Miao , Zhang Ridong
Published: July 2018

Average dwell time (ADT) of switched systems is dependent on two parameters: the decay coefficient of the subsystems and the increase coefficient of the Lyapunov functions of different subsystems, namely, and , respectively. In the literature, the two parameters are prescribed because popular computation techniques cannot deal with bilinear conditions easily. A new method for the computation of ADT is presented in this study, where a suggested optimisation algorithm is proposed to obtain a loose ADT condition. The advantages of the method lie in twofold: (i) the parameters and do not need to be given, and (ii) the presented ADT conditions are tractable to solve. The method is also extended to mode‐dependent ADT (MDADT), ADT in asynchronous control, and ADT and MDADT of positive switched systems.
Multi‐frequency dual polarisation radiometer common aperture antenna feeding system
Authors: Hongjian Wang , Qiyan Hao , Min Yi , Dehai Zhang , Xingchao Dong , Yang Liu , Xue Chen
Published: July 2018

This study presents a design of a tri‐band dual polarisation common aperture feed horn used for the radiometer. The proposed feeding system is made up of a corrugated horn, an orthomode transducer (OMT) and two pairs of a high‐pass filter (HPF) and a band‐pass filter (BPF). The broadband profiled corrugated horn loaded with teeth (rings) is adopted as the feed of the radiometer. Wideband finline OMT is developed to realise a bandwidth ratio in excess of 2:1. Two different HPFs and BPFs are employed to block and pass waves of different frequencies. The feeding structure is then simulated, fabricated and tested. The measured results show that the radiation patterns possess good symmetry at all three working frequencies of interest (18.7, 23.8 and 37 GHz). Furthermore, the cross‐polarisation levels are below −23 dB and voltage standing‐wave ratios are lower than 1.5 throughout all working bands.
Design of a 24 GHz FMCW radar system based on sub‐harmonic generation
Authors: El Agroudy Naglaa , El‐Shennawy Mohammed , Joram Niko , Ellinger Frank
Published: July 2018

This study presents a novel frequency modulated continuous wave (FMCW) radar system based on sub‐harmonic generation, where a 24 GHz frequency divider‐by‐10 is used as an active reflector tag. A practical prototype is designed and fabricated on a GF45nm‐Silicon on Insulator (SOI) technology for the 24 GHz building blocks, while a GF0.18 µm 7WL Bipolar Complementary Metal Oxide Semiconductor (BiCMOS) technology was used for the 2.4 GHz receiver and baseband. System measurement results show that as opposed to conventional primary radars, the proposed system is immune to strong multi‐path interferences resulting from direct reflections of the interrogating signal. The system achieves a ranging precision of 3.7 mm with loop measurements. Moreover, when measured in an indoor environment, the ranging results show a ranging precision and accuracy of 5.8 and 22.3 cm, respectively, which outperform other FMCW radars in the literature.
Low‐complexity GNSS anti‐spoofing technique based on Doppler frequency difference monitoring
Authors: Tu Jiaxun , Zhan Xingqun , Zhang Xin , Zhang Zhenjun , Jing Shuai
Published: July 2018

Single‐antenna global navigation satellite system (GNSS) spoofing, where all spoofing signals are broadcast by the same antenna, is a great threat to mass market location‐based services. This study proposes an anti‐spoofing technique based on Doppler frequency difference (DFD) monitoring against single‐antenna spoofing, which requires only a standalone receiver with a single antenna. When the receiver moves randomly, the DFD between two authentic satellite signals is non‐linear in time domain, whereas between two single‐antenna spoofing signals is linear. This study deduces the DFD model and converts the problem of spoofing detection into a sequence linearity detection problem. The hypothesis based on DFD is given, and the statistic is constructed by the method of sequence block processing. This technique has low complexity because it only requires the knowledge of the Doppler frequency without additional information. The detection performance is verified by simulations and real data experiments. The simulation results show that the detection probability can exceed 99.99% easily at 0.001% false alarm probability when the receiver's motion state changes sufficiently. The real data experiments show that the proposed technique can effectively detect GNSS spoofing and distinguish spoofing signals from authentic signals.
Two unbiased converted measurement Kalman filtering algorithms with range rate
Authors: Liu Hongqiang , Zhou Zhongliang , Yu Lei , Lu Chunguang
Published: July 2018

The strong non‐linear relationship between the range rate and the target state can be introduced using the range rate to track a target. A linear measurement equation can be constructed based on the geometrical relationship between the range rate and the velocity components. Then, the linear Kalman filtering (KF) algorithm can be used. To improve the performance of the converted measurement method, a novel multiplicative unbiased converted measurement KF algorithm with range rate (UCMKF‐R) is developed. To eliminate the conversion bias, one‐step prediction estimation is used to replace the position measurement to calculate the converted measurement error covariance in the UCMKF‐R algorithm, which removes the correlation between the converted measurement error covariance and the measurement noise. Thus, a Decorrelated UCMKF‐R (DUCMKF‐R) is proposed. The experimental results show that the measurement conversion of the DUCMKF‐R algorithm is unbiased, consistent and has an estimation bias that is close to zero. The proposed UCMKF‐R and DUCMKF‐R algorithms are compared with the state‐of‐the‐art approaches, namely, the Sequential Extended KF algorithm, the Sequential Unscented KF algorithm, and the Converted Measurement KF with Range Rate algorithm. The experimental results show that the proposed algorithms have good performance.
Optimal tone detection for optical fibre vector hydrophone
Authors: Peng Chengyan , Zhang Xueliang , Song Zhangqi , Meng Zhou
Published: July 2018

An optimal tone detector based on the Neyman–Pearson criterion is proposed for the optical fibre vector hydrophone (OFVH). The detector takes account of the difference between noise levels on the acoustic pressure channel and the three particle acceleration channels of an OFVH. Explicit expressions for the impulse responses of pre‐filters that are central to the proposed detector are given. Analyses show that the proposed detector is equivalent to the minimum variance distortionless response beamformer for the OFVH. In the case of identical noise on all particle acceleration channels, the signal‐to‐noise ratio (SNR) gain of the detector is dB ( is the noise power ratio of OFVH channels at the tone frequency), whereas the SNR gain also depends on target direction and is bounded by and dB when noise on all particle acceleration channels are different. Results from both simulations and lake experiment data show that the proposed detector outperforms tone detectors that use (i) the acoustic pressure signal, (ii) the particle acceleration signals and (iii) equally the combination of acoustic pressure signal and particle acceleration signals.
Analyses of launch sites lightning protection systems by 3D numerical modelling and experimental tests
Authors: Aslani Farshad , Yahyaabadi Mostafa , Vahidi Behrooz
Published: July 2018

The lightning progression model has been implemented in this article to study the performance of the lightning protection system to the launch site. For this purpose, a real‐size exemplary protective system has been used for simulation and a laboratory‐scale exemplary system has been applied for both simulation and experimental testing applications. Surveys and simulations are both conducted in a three‐dimensional space and vulnerable areas on equipment surface – areas with the greatest demolition potentiality are identified as well. Implementing various charge models, the protective system and the installation consisting of launch pad, spacecraft, three lightning towers and catenary wires is modelled at first and the impulse experiments are eventually performed on the lab‐made model in a high‐voltage laboratory. The good level of conformity observed between simulation and experimental test results verifies the above‐mentioned method accuracy and application to real‐size systems.
Relationship between PD magnitude distribution and pulse burst for positive coronas
Authors: Tang Ju , Luo Xinyu , Pan Cheng
Published: July 2018

Statistical characteristics of discharge magnitude are significant for insulation diagnosis by monitoring partial discharge (PD) in power apparatuses. However, hitherto, investigations on the PD magnitude distribution in SF6 gas under direct current voltage are insufficient. A current pulse measuring circuit and a ultra‐high‐frequency (UHF) antenna were simultaneously employed to investigate characteristics of positive corona in 0.3 MPa SF6 gas. It is found that compared to the UHF antenna, the common measurement impedance used in laboratories caused several current pulses overlapped, resulting in pulse burst phenomenon. The pulse burst was easily mistaken as a single PD, which actually contained several PDs, thereby negatively affecting obtaining a real discharge magnitude distribution. Moreover, the discharge magnitude distributions were compared when a pulse burst was treated as a single PD and several PDs, respectively. It is found the former and latter one had forms of non‐skewed two‐parameter Weibull distribution with large‐scale parameters and positively skewed two‐parameter Weibull distribution with small‐scale parameters, respectively. Based on this understanding, the change of the distributions with time was investigated, and the results showed that the distribution would have a permanent form of two‐parameter Weibull distribution after a 24‐h transition time.
Development of a high sensitive magnetic flux leakage instrument for imaging of localised flaws in small diameter ferromagnetic steel tubes
Authors: Sharatchandra Singh Waikhom , Mukhopadhyay Chandan Kumar , Purna Chandra Rao Bhagi
Published: July 2018

The authors report the development of a high sensitive, 16 channel magnetic flux leakage (MFL) instrument for imaging of localised flaws in small diameter ferromagnetic steel tubes. The instrument consists of a magnetising unit of two bobbin coils wound on a ferrite core, a sensing unit of flexible giant magneto‐resistive (GMR) sensor array and an image visualisation unit. 3D‐non‐linear finite‐element modelling has been carried out to optimise the inter‐coil spacing of the bobbin coils and to identify the number of GMR elements and their locations between the bobbin coils. A series of experiments has been carried out to evaluate the flaw detection performance of the MFL instrument. Studies reveal that the instrument can image as small as 1.1 mm diameter hole and 0.46 mm deep shallow outer diameter circumferential notch in 17.2 mm diameter Mod. 9Cr–1Mo steel tubes used as steam generator material in prototype fast breeder reactor, with a signal‐to‐noise ratio better than 8 dB. Studies also indicate that intensity of MFL signal measured by the instrument increases with increase in hole diameter and notch depth. The instrument is portable and easy to use for field inspection of ferromagnetic steel components.
Pattern recognition of unknown partial discharge based on improved SVDD
Authors: Gao Jiacheng , Zhu Yongli , Jia Yafei
Published: July 2018

The pattern recognition of a partial discharge (PD) is critical to evaluate the insulation condition of electric equipment of high voltage. However, much attention had been paid to recognise PD types which are known, but it is ignored that the types which did not appear previously. To solve the above problems, a method to recognise unknown PD types based on improved support vector data description (SVDD) algorithm is introduced in this study. Tri‐training algorithm and double thresholds set based on Otsu algorithm are used to improve the traditional SVDD classifiers. PD samples collected from different artificial defects models are finally classified by the improved fuzzy c‐means clustering algorithm. Experiments compared the improved SVDD with existing one‐class classification methods such as SVDD, one‐class support vector machine and probability density function estimation. The results show that the proposed method has much higher recognition accuracy. It is verified that the improved SVDD is an efficient method which can be applied to the recognition of unknown PD types.
Influences of surface tips of a shield ball on the discharge characteristics of a long sphere‐plane air gap under positive switching impulses
Authors: Geng Jianghai , Lv Fangcheng , Ding Yujian , Zhao Yingyu , Li Peng , Wang Ping
Published: July 2018

The study established a test platform for a long sphere‐plane air gap in the test hall of the ultra‐high voltage (UHV) direct current(DC) Testing Site. Under the sphere‐plane gaps with 3, 5 and 7 m distance, the study carried out the experiment on discharge characteristics under switching impulses on a shield ball on which surface tips had different lengths at different locations. By comparing with the test data obtained under conditions with a smooth surface of the shield ball and the same gap distance, the discharge laws under the influence of surface tips on the shield ball are shown as follows: the presence of the tips greatly decreased the discharge voltage of the sphere‐plane gap with the maximum decrease amplitude of 39.0%. Moreover, the decrease degree was increasingly significant with the growing length of tips. The influence of the same length of tips on the discharge voltage of the gap gradually declined with the growth of the gap distance. The presence of tips significantly reduced the discharge voltage, especially in the perpendicular line of the shield ball. The results indicate that it's necessary to strictly control the machining and installation to avoid the occurrence of tips in UHV DC engineering.
Facile design and fabrication of capillary valve for mixing using two‐step PDMS moulding
Authors: Lai Chia‐Chun , Chung Chen‐Kuei
Published: July 2018

The traditional capillary mixing using a closed channel and a mixing unit without the delay valve encounters problems of backflow and clogging. Here, the polydimethylsiloxane (PDMS) mixing channel with the facile delay valve and open surface design has been demonstrated using the two‐step moulding for long‐term‐hydrophilic capillary‐pumping. The triggering of delay valve before the mixing unit is controlled by the specific channel height calculated using capillary theory. It can eliminate the problems of backflow, clogging and bubble defect. Also, the channel height in an open channel is reduced to 150 µm compared to the close one of 250 µm by numerical analysis. The CO2‐laser‐ablated polymethylmethacrylate (PMMA) mother mould can avoid the complicated fabrication process using photolithography and SU8 mould. Using the unique two‐step PDMS moulding method can greatly diminish the defect from the laser‐ablated PMMA mould for a smoother surface. The naturally hydrophobic PDMS is modified using the polyethylene glycol and O2 plasma treatment to solve the sticking problem and prolong the hydrophilicity up to 164 h and more which is tested in the contact angle aging measurement.
Numerical study of the Vishniac instability in cooled supernova remnants
Authors: Minière J. , Bouquet S. E. , Michaut C. , Sanz J. , Mancini M.
Published: July 2018

Aims. The Vishniac instability is thought to explain the complex structure of radiative supernova remnants (SNRs) when a blast wave has propagated from a central explosion.

Methods. In this paper, we present numerical studies with the two-dimensional (2D) code HADES. We compare simulations of non-cooling perturbed SNRs, with simulations of perturbed SNRs experiencing radiative losses. In the first case, a low adiabatic index involves a high compression rate that can mimic the effect of radiative losses, whereas a cooling function is used in the second case.

Results. The development of the perturbation is analyzed with and without cooling. First, we show that with no cooling but with a low adiabatic index, the perturbation grows in agreement with the theory. Second, although in a first stage the initial Vishniac instability (VI) vanishes for SNR undergoing radiative losses and a large adiabatic index equal to 5/3, simulations show that at a later time a new and growing perturbation appears and the mode l′ of this new perturbation is twice the mode l of the initial one (l′ = 2 × l).

Conclusions. Simulating SNR evolutions in similar conditions to theoretical conditions, that is, an adiabatic expansion and adiabatic index lower than 1.2, VI is found to occur in accordance with theoretical predictions. When cooling, instead of a low adiabatic index, which is included in the model, simulations demonstrate that in the late stage of SNR evolution, a doubled mode VI develops even for an adiabatic index equal to 5/3. These two phenomena, VI for high adiabatic index and the mode doubling process, are new and demonstrated in this paper.
Spectroscopic diagnostics of dust formation and evolution in classical nova ejecta
Authors: Shore Steven N. , Paul Kuin N. , Mason Elena , De Gennaro Aquino Ivan
Published: July 2018

A fraction of classical novae form dust during the early stages of their outbursts. The classical CO nova V5668 Sgr (Nova Sgr. 2015b) underwent a deep photometric minimum about 100 days after outburst that was covered across the spectrum. A similar event was observed for an earlier CO nova, V705 Cas (Nova Cas 1993) and a less optically significant event for the more recent CO nova V339 Del (Nova Del 2013). This study provides a “compare and contrast” of these events to better understand the very dynamical event of dust formation. We show the effect of dust formation on multiwavelength high resolution line profiles in the interval 1200 Å–9200 Å using a biconical ballistic structure that has been applied in our previous studies of the ejecta. We find that both V5668 Sgr and V339 Del can be modeled using a grey opacity for the dust, indicating fairly large grains (≳0.1 μ) and that the persistent asymmetries of the line profiles in late time spectra, up to 650 days after the event for V5668 Sgr and 866 days for V339 Del, point to the survival of the dust well into the transparent, nebular stage of the ejecta evolution. This is a general method for assessing the properties of dust forming novae well after the infrared is completely transparent in the ejecta.
Signatures of multiple episodes of AGN activity in the core of Abell 1795
Authors: Kokotanekov G. , Wise M. W. , de Vries M. , Intema H. T.
Published: July 2018

In this paper we analyze AGN activity signatures in the rich nearby galaxy cluster Abell 1795 aiming to confirm and characterize the long-term feedback history in the system. We combine radio observations at 610 and 235 MHz from the Giant Metrewave Radio Telescope (GMRT) with 3.4 Msec X-ray data from the Chandra Observatory. Extracting radial temperature profiles, as well as X-ray and radio surface brightness profiles in three directions showing major morphological disturbances, we highlight the signatures of activity in the system. For the first time we observe radio emission corresponding to the NW X-ray depression, which provides evidence in favor of the classification of the depression as a cavity. We identify two other X-ray cavities situated NW and SW of the AGN. While the central radio emission corresponding to the inner cavities shows a flatter spectral index, the radio extensions associated with the farthest X-ray cavities consist of aged plasma. All observed signatures both in radio and X-ray are consistent with several consecutive episodes of AGN activity, which gave rise to the observed morphology NW and SW from the core. In the southern region, we confirm the cooling wake hypothesis for the origin of the long tail. The deep X-ray data also allows us to distinguish significant distortions in the tail’s inner parts, which we attribute to the activity of the AGN.
Stellar contributions to the line profiles of high-resolution transmission spectra of exoplanets
Authors: Borsa F. , Zannoni A.
Published: July 2018

Context. In-depth studies of exoplanetary atmospheres are starting to become reality. In order to unveil their properties in detail, we need spectra with a higher signal-to-noise ratio (S/N) and also more sophisticated analysis methods.

Aims. With high-resolution spectrographs, we can not only detect the sodium feature in the atmosphere of exoplanets, but also characterize it by studying its line profile. After finding a clearly w-shaped sodium line profile in the transmission spectrum of HD 189733b, we investigated the possible sources of contamination given by the star and tried to correct for these spurious deformations.

Methods. By analyzing the single transmission spectra of HD 189733b in the wavelength space, we show that the main sodium signal that causes the absorption in the transmission spectrum is centered on the stellar rest frame. We concentrate on two main stellar effects that contaminate the exoplanetary transmission spectrum: center-to-limb variations (CLVs) and stellar rotation. We show the effects on the line profile: while we correct for the CLV using simulated theoretical stellar spectra, we provide a new method, based directly on observational data, to correct for the Rossiter–McLaughlin contribution to the line profile of the retrieved transmission spectrum.

Results. We apply the corrections to the spectra of HD 189733b. Our analysis shows line profiles of the Na D lines in the transmission spectrum that are narrower than reported previously. The correction of the sodium D2 line, which is deeper than the D1 line, is probably still incomplete since the planetary radius is larger at this wavelength. A careful detrending from spurious stellar effects followed by an inspection in the velocity space is mandatory when studying the line profile of atmospheric features in the high-resolution transmission spectrum of exoplanets. Since the line profile is used to retrieve atmospheric properties, the resulting atmospheric parameters could be incorrectly estimated when the stellar contamination is not corrected for. Data with higher S/N coupled with improved atmospheric models will allow us to adapt the magnitude of the corrections of stellar effects in an iterative way.
Effect of noise on measurements of diffusivity in transparent liquid mixtures by digital speckle photography
Authors: De Leo Cinzia , Paoletti Domenica , Ambrosini Dario
Published: July 2018

Interfacing two liquid mixtures in a diffusion cell induces noise in the initial state of the diffusing system, which produces a gap between the diffusion boundary and the ideally boundary assumed in the theory. Measured diffusivity values systematically drift with time and they are often corrected by using a linear shift of the zero-time of the process after sufficiently long time when the system reaches the free one-dimensional diffusion regime. In data analysis methods which involve optical correlation between pairs of successive digital images of the cell, it is not easy to establish how long the transient lasts. We show that when the initial perturbation between solution and solvent relaxes slowly toward the diffusive regime no simple zero-time correction can be applied.
Investigation of the expansion dynamics of silicon plasmas generated by double nanosecond laser pulses
Authors: Min Q. , Su M. G. , Wang B. , Wu L. , He S. Q. , Sun D. X. , Cao S. Q. , Dong C. Z.
Published: July 2018

A systematic investigation of the expansion dynamics of plasma plumes generated by two Q-switched Nd:YAG lasers at 1064 nm wavelength operating on a silicon target was undertaken for the inter-pulse delay times of 0, 100, 200, and 400 ns using a technique involving fast-gated intensified charge-coupled device imaging. Our results indicate that the plasmas exhibit free expansion in a vacuum environment at an inter-pulse delay time of 0 ns. With increasing inter-pulse delay time, the plasma front becomes sharpened and an interaction boundary is formed. Moreover, using the radiation intensity distribution along the plasma axis of symmetry, the formation and evolution mechanism of the plasmas generated by the double pulses was analyzed at different inter-pulse delay times. Finally, the experimental results of the expansion of the plasma core and front were compared with a radiation hydrodynamics model and a drag model, and were found to be generally in good agreement.
A predictive model for plastic relaxation in (0001)-oriented wurtzite thin films and heterostructures
Authors: Markurt T. , Schulz T. , Drechsel P. , Stauss P. , Albrecht M.
Published: July 2018

In this work, we present an experimental and theoretical study of the process of plastic strain relaxation of (0001)-oriented wurtzite heterostructures. By means of transmission electron microscopy and atomic force microscopy, we show that plastic relaxation of tensile strained AlxGa1-xN/GaN heterostructures proceeds predominantly by nucleation of a-type misfit dislocations in the 13⟨112¯0⟩|0001 slip-system driven by a three-dimensional surface morphology, either due to island growth or due to cracking of the layer. Based on our experimental results, we derive a quantitative model for the dislocation nucleation process. With the shear stress gradients at the nucleation sites of a-type misfit dislocations obtained by the finite element method, we calculate the critical thickness for plastic relaxation of strained wurtzite films and heterostructures as dependent on the surface morphology. The crucial role of the growth mode of the film on the strain relaxation process and the resulting consequences is discussed in the paper.
Nonlinear optical response of a gold surface in the visible range: A study by two-color sum-frequency generation spectroscopy. II. Model for metal nonlinear susceptibility
Authors: Busson B. , Dalstein L.
Published: July 2018

We present a modeling of the nonlinear optical response of a metal surface in order to account for recent experimental results from two-color Sum-Frequency Generation (SFG) experiments on gold. The model allows calculating the surface and bulk contributions and explicitly separates free and bound electron terms. Contrary to the other contributions, the perpendicular surface component is strongly model-dependent through the surface electron density profiles. We consider three electron density schemes at the surface, with free and bound electrons overlapping or spilling out of the bulk, for its calculation. The calculated SFG signals from the metal rely only on bulk quantities and do not need an explicit definition of the density profiles. In the particular case of gold, when the free electrons overlap with the bound ones or spill out of the bulk, the free electron response completely dominates through the perpendicular surface terms. When the bound electrons spill out, the situation is more balanced, still in favor of the free electrons, with lower amplitudes and different dispersion line shapes. As for silver, the free electron contributions dominate and the calculated slow amplitude growth from blue to red follows the experimental trends.
The effects of size distribution functions on contact between fractal rough surfaces
Authors: Xu Kuo , Yuan Yuan , Chen Jianjiang
Published: July 2018

In the fractal rough surface characterized by Weierstrass-Mandelbrot function, the amount of asperities with frequency index n is γ times the amount of asperities with frequency index n-1. According to the property, the revised size distribution functions and truncated size distribution functions of asperities with frequency index n are developed for the two-dimensional and three-dimensional fractal rough surfaces, respectively. The relations between real contact area and total contact load are obtained. The comparison between predictions of present model, the revised MB model and experimental data are given. The results show these asperities whose frequency indexes range from nmin to nmin+5 are major contribution to real contact area and total contact load. For given initial frequency index and total contact load, the real contact area of present model is smaller than that of the revised MB model. With an increase in initial frequency index, the results of present model gradually approach to that of the revised MB model. When initial frequency index nmin is less than the elastic critical frequency index nec, the trends of present model are in better agreement with experiment than that of the revised MB model.