bluuebunny/crossref_metadata_2025 huggingface dataset:
Colonoscopic band ligation for internal hemorrhoids - A tertiary care experience
Authors: Jalihal Umesh , S. Satya Prakash B , B. Avinash , Karanth Dheeraj
Published: September 2019

Background and objectives: Rubber band ligation (BL) is the most widely used technique for treatment of symptomatic internal haemorrhoids (IH) that are refractory to conservative treatment. The aim of this study is to assess the efficacy of colonoscopic BL as therapy for symptomatic IH.

Methods: Patients seen at our center with symptomatic IH who underwent BL between January 2006 and December 2011 were included in this prospective study. The clinical and colonoscopic details were entered in uniform structured data forms.

Results: Two hundred and eighteen consecutive patients with symptomatic IH were enrolled in the study. The presentations were rectal bleeding in 150 (69%) and prolapse in remaining 68 (31%) patients. Twenty-four patients (11%) had chronic liver disease (child B-C). Same operator treated all the patients. The severity of the IH was classified by using Goligher grading system. The mean age of patients was 48.3 + 15 years with range of 22 - 85 years. The mean follow up was 3months (range 1 month - 36 months). In 209 patients (96%) there was at least 1 grade reduction in hemorrhoids as well the symptoms were controlled. Two patients required surgery and another 7 patients required repeat session of banding. After banding session 32 (15%) patients had perianal pain and 13 (6%) had mild bleeding.

Conclusions: Colonoscopic BL is a safe, and effective outpatient therapeutic procedure for symptomatic internal hemorrhoids. Furthermore, the BL is safe and effective in patients of coagulopathy associated with chronic liver disease. (J Dig Endosc 2013;4(1):6–9)
Successful completion of upper gastrointestinal endoscopy: A retrospective comparative study on patients who had endoscopy with sedation and without sedation
Authors: Davies Joseph Benjamin , Roy Sunil Kanti
Published: September 2019

Introduction: Sedation of patients before esophagoduodenoscopy (EGD) is common practice. It is expensive, increases the time required to perform the procedure and increases risks of complications. We have set out to determine if sedation improves EGD completion rates.

Methods: 1539 EGDs were performed in the UK by an experienced endoscopist. The age, sex, premedication and completion data made at each procedure were recorded. A completed procedure was defined by the ability of the endoscopist to reach the second part of the duodenum. We measured the difference in the completion rates of EGD between sedated and non sedated patients.

Results: The completion rate for all procedures was 96.6%. 97.8% of procedures were complete in non sedated patients vs. 94.7% in sedated patients (p = 0.001). Male patients were more likely to have the EGD without sedation, as were those over the age of 65. There were no significant differences in the completion rates of EGD between patients who received IV sedation plus topical local anesthesia and those who received IV sedation alone.

Conclusion: The effect of sedation on EGD completion rates is previously undocumented. In order to reduce numbers of failed procedures and prevent exposing patients to the risks of sedation, we suggest these patients should be targeted for more intense pre-procedure counseling. Adequate explanation and reassurance may reduce numbers of patients who request IV sedation by reducing anxiety and increasing expectations of comfort. Reducing numbers of sedated patients may also result in a faster, more cost effective service. (J Dig Endosc 2013;4(2):33-38)
A comparative study of epitaxial InGaAsBi/InP structures using Rutherford backscattering spectrometry, X-ray diffraction and photoluminescence techniques
Authors: Sharpe M. K. , Marko I. P. , Duffy D. A. , England J. , Schneider E. , Kesaria M. , Fedorov V. , Clarke E. , Tan C. H. , Sweeney S. J.
Published: September 2019

In this work, we used a combination of photoluminescence (PL), high resolution X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) techniques to investigate material quality and structural properties of MBE-grown InGaAsBi samples (with and without an InGaAs cap layer) with targeted bismuth composition in the 3%–4% range. XRD data showed that the InGaAsBi layers are more homogeneous in the uncapped samples. For the capped samples, the growth of the InGaAs capped layer at higher temperature affects the quality of the InGaAsBi layer and bismuth distribution in the growth direction. Low-temperature PL exhibited multiple emission peaks; the peak energies, widths, and relative intensities were used for comparative analysis of the data in line with the XRD and RBS results. RBS data at a random orientation together with channeled measurements allowed both an estimation of the bismuth composition and analysis of the structural properties. The RBS channeling showed evidence of higher strain due to possible antisite defects in the capped samples grown at a higher temperature. It is also suggested that the growth of the capped layer at high temperature causes deterioration of the bismuth-layer quality. The RBS analysis demonstrated evidence of a reduction of homogeneity of uncapped InGaAsBi layers with increasing bismuth concentration. The uncapped higher bismuth concentration sample showed less defined channeling dips suggesting poorer crystal quality and clustering of bismuth on the sample surface.
Compositional accuracy in atom probe tomography analyses performed on III-N light emitting diodes
Authors: Di Russo E. , Cherkashin N. , Korytov M. , Nikolaev A. E. , Sakharov A. V. , Tsatsulnikov A. F. , Bonef B. , Blum I. , Houard J. , Da Costa G. , Blavette D. , Rigutti L.
Published: September 2019

Laser-assisted atom probe tomography (APT) and high-resolution dark-field electron holography (HR-DFEH) were performed to investigate the composition of a polar [0001] GaN/AlxGa1 − xN/InyGa1 − yN light emitting diode. In particular, the III-site fraction of both AlxGa1 − xN and InyGa1 − yN alloys was studied adopting a comparative approach. HR-DFEH allows mapping the projected strain with a subnanometer spatial resolution which is used for the calculation of the two-dimensional alloy composition distribution. APT provides three-dimensional alloys composition distribution with a nanometer spatial resolution. However, here we reveal that important inaccuracies affect local composition measurements. A Ga-poor composition is obtained in high DC-electric field regions. Moreover, such inaccuracies may be locally enhanced where the [0001] pole intersects the surface of the analyzed specimen, leading to a lower fraction of Ga measured. III-site fractions closer to the nominal values were measured at low field conditions. Ga loss is thought to be due to preferential DC field induced evaporation of Ga ions between laser pulses. This is explained in terms of formation of a metallic layer on the tip surface during APT analysis, where weak Ga-Ga bonds are formed, promoting the loss of Ga at high field conditions.
Verification of gyrokinetic particle simulation of current-driven instability in fusion plasmas. IV. Drift-tearing mode
Authors: Shi Hao , Zhang Wenlu , Feng Hongying , Lin Zhihong , Dong Chao , Bao Jian , Li Ding
Published: September 2019

The drift-tearing instability due to diamagnetic drift effects is verified using the Gyrokinetic Toroidal Code (GTC). First, the classical (2,1) resistive tearing mode is verified in a cylindrical geometry with a fluid model. The dependence of the growth rate of the resistive tearing mode on the beta value of the plasma is obtained and is found to qualitatively agree with the theoretical prediction. A drift-tearing mode is subsequently generated when the equilibrium pressure gradient is significant. In this mode, diamagnetic drift effects result in a reduced growth rate and a real frequency equal to the electron diamagnetic frequency. The scaling relation between the diamagnetic frequency and the growth rate of the drift-tearing mode has been calculated. This relation shows good agreement with the theoretical prediction for a relatively small resistivity; however, an obvious deviation arises when the resistivity is large.
Optimal motion of triangular magnetocapillary swimmers
Authors: Sukhov Alexander , Ziegler Sebastian , Xie Qingguang , Trosman Oleg , Pande Jayant , Grosjean Galien , Hubert Maxime , Vandewalle Nicolas , Smith Ana-Sunčana , Harting Jens
Published: September 2019

A system of ferromagnetic particles trapped at a liquid-liquid interface and subjected to a set of magnetic fields (magnetocapillary swimmers) is studied numerically using a hybrid method combining the pseudopotential lattice Boltzmann method and the discrete element method. After investigating the equilibrium properties of a single, two, and three particles at the interface, we demonstrate a controlled motion of the swimmer formed by three particles. It shows a sharp dependence of the average center-of-mass speed on the frequency of the time-dependent external magnetic field. Inspired by experiments on magnetocapillary microswimmers, we interpret the obtained maxima of the swimmer speed by the optimal frequency centered around the characteristic relaxation time of a spherical particle. It is also shown that the frequency corresponding to the maximum speed grows and the maximum average speed decreases with increasing interparticle distances at moderate swimmer sizes. The findings of our lattice Boltzmann simulations are supported by bead-spring model calculations.
Plastic Flow of Solid 4He and 3He at Low Temperatures (Review Article)
Authors: Maidanov V. A. , Rudavskii E. Ya. , Smirnov S. N. , Sokolov S. S.
Published: September 2019

A review of experimental and theoretical studies of the plastic flow of solid helium in the temperature range of 0.1–1.0 K is presented. The most reliable and interesting results were obtained in the two scientific groups where a plastic flow was observed between interconnected chambers containing solid helium that occurred after an overpressure in one of the chambers, and in which the direct contact of solid helium with the superfluid phase was excluded in the measuring cell. A significantly different nature of plastic flow was found in solid 4He and 3He: if in solid 4He the plastic flow rate decreases with decreasing temperature, which corresponds to a thermally activated process, then in solid 3He at temperatures below ≈0.2 K, quantum creep was first recorded when the flow rate ceased to depend on temperature. Only in one group in the experiments conducted near the melting curve, an increase in the flow rate of 4He was observed with decreasing temperature, which allowed the authors to conclude that some form of superfluidity manifested itself. In the thermally activated region of the plastic flow of 4He and 3He, the values of the activation energy and the activation volume, where the activation volume exceeds the atomic volume by a factor from 30 to 70. The analysis of the possible physical mechanisms of plastic flow of solid helium was carried out.
Effects of InAlN underlayer on deep traps detected in near-UV InGaN/GaN single quantum well light-emitting diodes
Authors: Polyakov A. Y. , Haller C. , Smirnov N. B. , Shiko A. S. , Shchemerov I. V. , Chernykh S. V. , Alexanyan L. A. , Lagov P. B. , Pavlov Yu. S. , Carlin J.-F. , Mosca M. , Butté R. , Grandjean N. , Pearton S. J.
Published: September 2019

Two types of near-UV light-emitting diodes (LEDs) with an InGaN/GaN single quantum well (QW) differing only in the presence or absence of an underlayer (UL) consisting of an InAlN/GaN superlattice (SL) were examined. The InAlN-based ULs were previously shown to dramatically improve internal quantum efficiency of near-UV LEDs, via a decrease in the density of deep traps responsible for nonradiative recombination in the QW region. The main differences between samples with and without UL were (a) a higher compensation of Mg acceptors in the p-GaN:Mg contact layer of the sample without UL, which correlates with the presence of traps with an activation energy of 0.06 eV in the QW region, (b) the presence of deep electron traps with levels 0.6 eV below the conduction band edge (Ec) (ET1) and at Ec 0.77 eV (ET2) in the n-GaN spacer underneath the QW, and the presence of hole traps (HT1) in the QW, 0.73 eV above the valence band edge in the sample without UL (no traps could be detected in the sample with UL), and (c) a high density of deep traps with optical ionization energy close to 1.5 eV for the LEDs without UL. Irradiation with 5 MeV electrons led to a strong decrease in the electroluminescence (EL) intensity in the LEDs without UL, while for the samples with UL, such irradiation had little effect on the EL signal at high driving current, although the level of driving currents necessary to have a measurable EL signal increased by about an order of magnitude. This is despite the 5 times higher starting EL signal of the sample with UL. Irradiation also led to the appearance in the LEDs with UL of the ET1 and HT1 deep traps, but with concentration much lower than without the UL, and to a considerable increase in the Mg compensation ratio.
Hotspot relaxation time in disordered niobium nitride films
Authors: Zhang Lu , You Lixing , Yang Xiaoyan , Tang Yan , Si Mengting , Yan Kaixin , Zhang Weijun , Li Hao , Zhou Hui , Peng Wei , Wang Zhen
Published: September 2019

The hotspot relaxation time (τth) was systematically studied on superconducting nanowire single-photon detectors (SNSPDs) made from ultrathin NbN films with different substrates and chemical compositions. The τth values were measured to be between 9.2 ps and 41.1 ps at the bath temperature of 2.15 K. The temperature dependence of τth ∝ TC−1.5 was observed, which indicated a dominant electron-phonon scattering relaxation mechanism in disordered NbN films. In addition, the increase in τth results in a higher latching probability in NbN-based SNSPDs with the same electrical response time (τe). The experimental results confirmed that the devices suffered latching when the ratio of the electric and thermal relaxation time was less than 133. This observation is an interesting reference for the design and process optimization of SNSPDs.
Binary mixtures of semicrystalline polymers with low-molecular-mass compounds: thermal behaviour and phase structure
Authors: Pochivalov Konstantin V. , Basko Andrey V. , Kudryavtsev Yaroslav V.
Published: September 2019

The results of phase equilibrium studies in mixtures of semicrystalline polymers with low-molecular-mass compounds are summarized and analyzed. A new classification of phase diagrams for such mixtures is proposed. Alternative points of view on the phase composition of semicrystalline polymers are presented. The phase structure evolution during the thermally induced phase separation of mixtures is monitored and the morphology of the forming capillary porous bodies as precursors of polymeric membranes is described. The general regularities concerning the influence of the nature of mixture components, polymer molecular mass, temperature scanning rate and other factors on the topology of phase diagrams are considered. Experimental methods used to construct the phase diagrams of mixtures and to study features of their phase structure are compared.

The bibliography includes 203 references.
Lead chalcogenide quantum dots for photoelectric devices
Authors: Shuklov Ivan A. , Razumov Vladimir F.
Published: September 2019

The review concerns the state of the art in methods of synthesis of colloidal lead chalcogenide quantum dots (QDs). The most recent data on the mechanisms of chemical transformations involving various precursors are discussed. Particular attention is paid to the influence of (i) trace impurities in the reactants used and (ii) post-synthesis treatment on the physicochemical properties of QDs used in photoelectric devices.

The bibliography includes 129 references.
The Safavid-Qizilbash Ecumene and the Formation of the Qizilbash-Alevi Community in the Ottoman Empire, c. 1500–c. 1700
Authors: Yıldırım Rıza
Published: September 2019

Alevis, the largest religious minority of Turkey, also living in Europe and the Balkans, are distinguished from both Sunnis and Shiʿites by their latitudinarian attitude toward Islamic Law. Conceptualizing this feature as “heterodoxy,” earlier Turkish scholarship sought the roots of Alevi religiosity in Turkish traditions which traced back to Central Asia, on the one hand, and in medieval Anatolian Sufi orders such as the Yasawi, Bektashi, Qalandari, and Wafaʾi, on the other. A new line of scholarship has critiqued the earlier conceptualization of Alevis as “heterodox” as well as the assumption of Central Asian connections. In the meantime, the new scholarship too has focused on medieval Anatolian Sufi orders, especially the Bektashi and Wafaʾi, as the fountainhead of Alevi tradition. Critically engaging with both scholarships, this paper argues that it was the Safavid-Qizilbash movement in Anatolia, Azerbaijan, and Iran rather than medieval Sufi orders, that gave birth to Alevi religiosity.
Rethinking Idris-i Bidlisi: An Iranian Bureaucrat and Historian between the Shah and the Sultan
Authors: Genç Vural
Published: September 2019

A bureaucrat and historian of Iranian origin, Idris-i Bidlisi (b. Ray/Iran 1457–d. Istanbul 1520), is undoubtedly one of the most original and important intellectual figures in the Ottoman‒Iranian borderland in the sixteenth century. He lived in a very turbulent period and established different relationships with Iranian and Ottoman dynasties at the end of the fifteenth century and at the beginning of the sixteenth century. He and his works have been the focus of long-standing historical debates in Turkey that have continued to the present day. Until now, most modern scholarly works on Bidlisi have failed to provide a proper, in-depth textual and historical analysis. As a result, such modern works have come to present a skewed, romanticized image of Bidlisi, largely detached from the nature and dynamics of the historical context in which Bidlisi lived and evolved as an intellectual and writer. This paper provides a realistic appraisal of Bidlisi and discusses the shortcomings of modern historiography on him. By looking at Bidlisi and his corpus, and more specifically at the ways in which the latter was shaped by Bidlisi’s patronage relationships, the paper aims to open up a window into Bidlisi’s evolving mindset and worldview. In other words, through an in-depth analysis of his corpus and new archival sources the paper strives to unveil the intellectual life and career of an Iranian bureaucrat and historian positioned between Ottoman‒Iranian borderland and provide a glimpse into the nature of patronage in the sixteenth century.
Encoding of speech in noise in adults using hearing aids
Authors: El-Assal Hiba Ahmed , El-Gharib Amani Mohamed , Kolkaila Enaas Ahmad , Elmahallawy Trandil Hassan
Published: September 2019

Introduction:

Subjects using hearing aids complains of difficulty in speech understanding in noise. Speech auditory brainstem response (S-ABR) provides cues for temporal and spectral encoding of speech in the brainstem.

Objective:

This work was designed to evaluate speech processing in patients fitted with hearing aid using S-ABR and to study the effect of noise reduction algorithm on speech processing in patients fitted with hearing aids.

Materials and method:

This study included 20 adults with mild to severe SNHL fitted with HA at least 3 months with aided threshold in all frequencies better than or equal to 30 dB. Hearing aid was used with all the subjects and was programed for each subject according to his audiogram followed by aided evaluation using S-ABR. Through sound field in four different test conditions with NR algorithm on in quiet and in the presence of noise then with the NR off in quiet and in the presence of noise were performed.

Results:

There was a statistically significant delay in the S-ABR onset and offset in noise compared to quiet. The effect of noise on S-ABR while the NR was on showed statistically significant difference in the onset response in both quiet and noise. When the NR was off, there was marked effect of noise on both the onset response and offset response.

Conclusions:

It was found that hearing aid users are vulnerable to noise regarding the speech encoding at the level of the brainstem. Noise reduction algorithm maintains the neural activity in response to speech and improves speech perception in noise.
Navigating between international recognition paradigms: prospects and challenges for Nagorno Karabakh
Authors: Ter-Matevosyan Vahram , Ghazaryan Edita
Published: September 2019

The Nagorno Karabakh conflict remains a perplexing challenge for the regional security of the South Caucasus. In spite of decades of negotiations under the auspices of the OSCE Minsk Group, the final resolution of the conflict remains a distant goal. Against this background, since 2012 several US and Australian states as well as the Basque Parliament started to support the right of the people Nagorno Karabakh to self-determination. The resolutions passed by these states were not only unprecedented but were also inconsistent with the foreign policies of their federal governments. The present paper examines the underlying reasons for nine US states (California, Rhode Island, Massachusetts, Michigan, Georgia, Hawaii, Maine, Louisiana, and Colorado), and the most populous state of Australia, New South Wales, to have recognized the right of the people of Nagorno Karabakh to self-determination. The paper also looks at the legal and political implications deriving from these resolutions as well as possible prospects for this pattern of recognitions. The paper argues that recognition of de facto states by federal sub-states is a new, albeit isolated, phenomenon. It may potentially enhance visibility of de facto states and help them to gain more support for their pursuit of international recognition.
Reconstruction of attosecond pulses in the presence of interfering dressing fields using a 100 kHz laser system at ELI-ALPS
Authors: Hammerland D , Zhang P , Kühn S , Jojart P , Seres I , Zuba V , Varallyay Z , Charalambidis D , Osvay K , Luu T T , Wörner H J
Published: September 2019

Attosecond Pulse Trains (APT) generated by high-harmonic generation (HHG) of high-intensity near-infrared (IR) laser pulses have proven valuable for studying the electronic dynamics of atomic and molecular species. However, the high intensities required for high-photon-energy, high-flux HHG usually limit the class of adequate laser systems to repetition rates below 10 kHz. Here, APT’s generated from the 100 kHz, 160 W, 40 fs laser system (HR-1) currently under commissioning at the extreme light infrastructure attosecond light pulse source (ELI-ALPS) are reconstructed using the reconstruction of attosecond beating by interference of two-photon Transitions (RABBIT) technique. These experiments constitute the first attosecond time-resolved photoelectron spectroscopy measurements with attosecond pulses performed at 100 kHz repetition rate and one of the first experiments performed at ELI-ALPS in the framework of projects commissioning its newly installed technologies. These RABBIT measurements were taken with an additional IR field temporally locked to the extreme-ultraviolet APT, resulting in an atypical ω beating. We show that the phase of the 2ω beating recorded under these conditions is strictly identical to that observed in standard RABBIT measurements within second-order perturbation theory. This work highlights an experimental simplification for future experiments based on attosecond interferometry (or RABBIT), which is particularly useful when lasers with high average powers are used.
Channeling effects in gold nanoclusters under He ion irradiation: insights from molecular dynamics simulations
Authors: Ghaderzadeh Sadegh , Ghorbani-Asl Mahdi , Kretschmer Silvan , Hlawacek Gregor , Krasheninnikov Arkady V
Published: September 2019

The interpretation of helium ion microscopy (HIM) images of crystalline metal clusters requires microscopic understanding of the effects of He ion irradiation on the system, including energy deposition and associated heating, as well as channeling patterns. While channeling in bulk metals has been studied at length, there is no quantitative data for small clusters. We carry out molecular dynamics simulations to investigate the behavior of gold nanoparticles with diameters of 5–15 nm under 30 keV He ion irradiation. We show that impacts of the ions can give rise to substantial heating of the clusters through deposition of energy into electronic degrees of freedom, but it does not affect channeling, as clusters cool down between consecutive impact of the ions under typical imaging conditions. At the same time, high temperatures and small cluster sizes should give rise to fast annealing of defects so that the system remains crystalline. Our results show that ion-channeling occurs not only in the principal low-index, but also in the intermediate directions. The strengths of different channels are specified, and their correlations with sputtering-yield and damage production is discussed, along with size-dependence of these properties. The effects of planar defects, such as stacking faults on channeling were also investigated. Finally, we discuss the implications of our results for the analysis of HIM images of metal clusters.
Some Features of Geometric Nonlinear Damping on Isolation Performance
Authors: Gatti G , Tehrani M G
Published: September 2019

The addition of nonlinear characteristics to improve the dynamic performance of isolation systems and vibration absorbers has been extensively investigated in the past decades. Both nonlinear stiffness and nonlinear damping have been largely analysed. A common way in which this can be achieved in practice, is by arranging linear elements (springs and viscous dampers) in a specific geometrical configuration. This paper focuses on the fundamental effect of geometrical nonlinear damping in a vibration isolation system, and briefly revises two of the classical implementation mechanisms. They can achieve a better performance than linear systems, by assuring lower damping force at lower displacements, and higher damping force at higher displacements. However, strong nonlinear effects can manifest around resonances, causing non-negligible higher-order harmonics to appear, and making the approximate frequency response obtained by the harmonic balance, unuseful. This paper proposes a new strategy to limit such undesired dynamic effects. For this aim, a coupling is introduced on purpose in the damping mechanism, which allows tailoring the damping force for the specific need.
Dynamic analysis of vibrating flip-flow screens equipped with support and shear rubber springs
Authors: Gong Sanpeng , Oberst Sebastian , Wang Xinwen
Published: September 2019

Vibrating flip-flow screens provide an effective means of screening highly viscous or fine materials, and the dynamic characteristics of the main and the floating screen frames are largely responsible for a flip-flow screen’s screen performance and its processing capacity. An accurate dynamic model of the rubber shear springs used within the frame of the screen is critical for its dynamic analysis – to understand deficiencies and improve its performance. In this paper, the Sjöberg model is used to predict the frequency-and amplitude-dependent behaviour of the rubber shear springs. A friction model represents the amplitude dependency of the rubber shear springs. The fractional derivative model is used to describe its frequency dependency with its elasticity being represented by a linear spring. This model is further validated by cyclic tests of the rubber shear springs. Furthermore, dynamic response of the VFFS have been analysed using the Sjöberg model and the Kelvin-Voigt model, respectively. Experimental results indicate that dynamic response of VFFS can be better predict using the Sjöberg model than Kelvin-Voigt model in time region as well as in the frequency domain.
A substantial rise in the area and population affected by dryness in South Asia under 1.5 °C, 2.0 °C and 2.5 °C warmer worlds
Authors: Aadhar Saran , Mishra Vimal
Published: September 2019

Millions of people in South Asia face water scarcity every year. Previous studies based on the multi-model ensemble mean reported a decline in dryness (the ratio of potential evapotranspiration and precipitation) in South Asia under the warming climate. However, using observations and simulations from skilful climate models (BEST-GCMs) that simulate the critical monsoon features and show less bias to simulate observed climate, we show that dryness has significantly increased over the Gangetic Plain and parts of Pakistan during 1951–2016. Moreover, a rise in global mean temperature of 1.5 °C from the pre-industrial level will result in an increased dryness over half of South Asia affecting more than 790(±336) million people. Population affected by dryness is projected to 890 (±485) and 1960 (±1033) million under 2.0° and 2.5° warming worlds, respectively. Previously reported reduced aridity under the warming climate based on multi-model ensemble is mainly due to the GCMs that have less skill to simulate monsoon features. The GCMs with less skill project a higher increase (∼25%) in the monsoon season precipitation, which is largely due to their higher sensitivity of convective precipitation to warming. We show that the risk of water scarcity and dryness in South Asia under warming climate is higher than previously reported.
Low-frequency resonant vibration energy harvester using piezoelectric stacks with force magnification frames
Authors: Duan Xiangjian , Cao Dongxing
Published: September 2019

The piezoelectric stack energy harvester (PSEH) is often used to transform ambient large amplitude vibrational energy, such as road vibrations and pressure fluctuations, because of its ability to withstand large external excitation force. However, due to the high natural frequency of the piezoelectric stack, it is difficult to generate resonance phenomenon, which leads to low energy efficiency for the energy harvester. In this paper, a piezoelectric stack energy harvester with force magnification frame (FMF) is proposed and studied for energy harvesting from low-frequency pressure ripples. First, a force magnification frame is designed to enhance the pressure transferring ability. The FMF is able to, not only amplify the exciting force acting on the piezoelectric stack but also decrease the natural frequency of the PSEH. Based on finite element method (FEM) analysis, the natural frequency of the PSEH with FMF is obtained. The natural frequency of the PSEH is successfully reduced, and the open-circuit voltage output of the PSEH under low-frequency resonance conditions is much higher than for off-resonance conditions. The results validate that the PSEH with FMF is efficient for lower frequency vibration environments.
Vortex-induced vibrational tristable energy harvester: Design and experiments
Authors: Zhou S , Li J , Wang J , Li G , Wang Q
Published: September 2019

Wind energy harvesters have been widely studied for their great application potential to power small wireless sensors. Meanwhile, the unique dynamic characteristics of vibrational tristable energy harvesters have been theoretically and experimentally verified. More importantly, such vibrational tristable energy harvesters have excellent broadband energy harvesting performance under low-frequency and low-level excitations. This paper aims to develop a new kind of aeroelastic energy harvesters for enhancing wind energy harvesting performance. In detail, a vortex-induced vibrational tristable energy harvester is designed by using the magnetic force to realize the tristable configuration. A mathematical model of the presented harvester is provided. Experimental results verify that the presented vortex-induced vibrational tristable energy harvester performs better than the traditional linear vortex-induced vibration energy harvester.
Theoretical and experimental study of bistable symmetric shells built by locally nanostructuring an isotropic plate
Authors: Yi Shenghui , He Xiaoqiao , Lu Jian
Published: September 2019

A new bistable symmetric isotropic shell is proposed and studied by using nano-technique, surface mechanical attrition treatment (SMAT), to locally treat a rectangular region within a plate. Plastic deformations accumulate in the treated region with the impacts from randomly fast moving balls during the process. The impacts also induce nanotwins and mesh the grains of the material into nanoscales, which largely increase the elastic deformation ability of the processed plate. With sufficient plastic deformations accumulated and stretching the plate under the constraint from the untreated region, the induced residual stress field buckles the plate to hold two different stable configurations and, thus, the bistable characteristic is generated for the nanostructured plate. A numerical model is developed to predict the stable configurations with verification by experiments. The parameters to design the stable configurations of the bistable shells are systematically discussed experimentally and numerically.
Detection and analysis of high temperature fatigue fracture surface oxygen diffusion of GH4133B superalloy used in turbine disk of aero-engine
Authors: Zhao R G , Deng L Y , Liu Y F , Ji N , Ren C L , Li X M
Published: September 2019

The chemical contents on the fatigue fracture surface of GH4133B superalloy piece suffering tension-tension fatigue and operated at high temperature 600 ºC is analyzed using an energy dispersive spectrometer, and the element content percentages at the position of carbide inclusion and that of second-phase particle in the fatigue source region are measured. It is shown that under the conditions of high temperature and air environment, the carbon element in the carbide inclusion can be easily oxidized, which results in accelerating fatigue crack nucleation and microcrack generation, reducing the fatigue crack initiation lifetime. The oxygen concentration is detected on the fatigue fracture surface along the crack propagation direction, the oxygen diffusion model is constructed, and the oxygen concentration gradient equation is derived. It is found that the oxygen content decreases gradually along the crack propagation direction, suggesting that at the crack initiation and short crack propagation stage, the alloy element reacts sufficiently with oxygen for a long time, and the oxidation accelerates the crack initiation, while at the long crack growth stage, the crack propagation rate is faster, so the alloying elements do not have adequate time for reacting with oxygen, resulting in the low oxygen content, and the oxidation has a small influence on the long crack propagation rate.
Simulation and experimental research on ultrasonic drawing of copper shaped wires
Authors: Liu S , Xie T , Cao H Q , Shan X B
Published: September 2019

Ultrasonic vibrations contribute to drawing force reduction and surface finish improvement in the production of round wires. However, their effects on the drawing of irregular-shaped wires are rarely reported, as the process involves not only the shrinkage but also the reshaping of the cross-sections, which increases the difficulty in both numerical and experimental research. This work aims to investigate the influences of ultrasonic amplitude, drawing velocity, and area reduction ratio on the drawing force during the manufacturing of copper wires with rectangular, pentagon, and hexagon cross sections. The surface microtopography of the wire products was inspected using the Leica digital microscope and Hitachi scanning electron microscope (SEM). A remarkable drawing force reduction by up to 47% was observed when ultrasonic vibrations were added, especially for larger ultrasonic amplitude and lower drawing velocity occasions. The surface finish, however, was actually worse compared with under conventional drawing conditions, especially when ultrasonic amplitude exceeded 7 μm. This paper provides a potentially valuable method to enhance the efficiency of industrial production of irregular-shaped wires.
Analysis of high temperature fatigue lifetime of GH4133B superalloy used in turbine disk of aero-engine
Authors: Ren C L , Zhao R G , Liu Y F , Ji N , Deng L Y , Li X M
Published: September 2019

Based on the S-H cavity model theory and the thermodynamic diffusion equation, the high temperature fatigue lifetime equation is deduced, and the influence of stress amplitude and mean stress on fatigue lifetime is quantitatively analyzed. At high temperature of 650°C, according to the test data of fatigue lifetime of GH4133B superalloy under different stress ratios or alternatively at various maximum stress levels, the nonlinear regression analysis method is applied to identify the material parameters in the fatigue lifetime equation, and a 3D N
f-σm-σa curve surface is plotted. The comparison between theoretic fatigue lifetime N
fp and test one N
ft indicates that the fatigue lifetime equation derived from the microstructure evolution of metallic materials can accurately predict the fatigue lifetime of GH4133B superalloy under different cyclic loading parameters. Finally, a parameter γ is introduced to characterize the effect of mean stress σm and stress amplitude σa on fatigue lifetime N
f of GH4133B superalloy. It is suggested that the effect of mean stress σm on N
f is larger than that of stress amplitude σa on N
f under the condition of tensile-tensile fatigue loading.
Nonlinear dynamics and parameter control for metamaterial plate with negative Poisson’s ratio
Authors: Zhu S T , Li J , Zhou J , Quan T T
Published: September 2019

The metamaterial with negative Poison’s ratio is widely used due to its special mechanical and physical properties. Based on the theory of periodic solution and bifurcation of nonlinear dynamics, we mainly focus on the nonlinear vibration behaviors and parameter control of a simply supported concave hexagonal composite sandwich plate with negative Poisson’s ratio in auxetic honeycombs subjected to in-plane and transverse excitation. The Melnikov function is improved by introducing the curvilinear coordinate frame and Poincaré map to detect the existence and number of the periodic solutions. The effects of the forcing excitation coefficient on nonlinear dynamics as well as the parameter control conditions are presented. Numerical method is performed to obtain the phase portraits of the number and corresponding positions of multiple periodic orbits.
Integrated design of structure and anisotropic material based on the BESO method
Authors: Yan X L , Xu Q W , He J , Huang D F , Huang X D
Published: September 2019

An Integrated structural and material topology optimization method considering optimal material orientation is presented based the on bi-direction evolutionary structural optimization (BESO) method. It is assumed that the macrostructure is composed of uniform cellular material but with different orientation. The homogenization method is used to calculate the effective material properties which builds a connection between material and structure. The continuous material orientation design variables and the discrete topology design variables are treated hierarchically in an iteration. The principal stress method is adopted and embedded to determine the optimal material orientation, meanwhile the topologies of the macrostructure and its material microstructure are concurrently optimized by using the BESO method. Numerical examples are conducted to demonstrate the effectiveness of the proposed optimization algorithm.
Low-velocity impact response of 3D-printed lattice sandwich panels
Authors: Wang Sheng , Xu Yingjie , Zhang Weihong
Published: September 2019

This paper investigates the low velocity response of sandwich panels with four different lattice cores by conducting drop-weight impact tests. Sandwich panels are made of galvanized sheet and 3D-printed lattice cores in this study. Four different types of lattice, including body-centered cubic (BCC), z-reinforced body-centered-cubic (BCCz), gyroid lattice and Schwarz P lattice, are selected for the cores of sandwich panels respectively. Functional graded versions of these lattices are also examined, which features a density gradient along impact direction. Low-velocity impact response of a solid sandwich panel with the same quality is tested as a comparison. Experimental results show that lattice sandwich panels absorb more energy compared with solid sandwich panels. In addition, the graded lattice cores can further improve the energy absorption capacity of sandwich panels.
Failure analysis of composite tube hinge and optimization design
Authors: Li Bowen , Ye Hongling , Zhang Yang
Published: September 2019

Composite materials with intriguing mechanical properties are introduced into special deployable structure. The tube hinge in this research is investigated, which has a base tube structure with one slot. However, due to large rotation and large nonlinearity, the composite tube hinge has material failure, thus leading to deployment failure. To overcome the problem, Hashin failure criterion is used for checking the extent to which the material is damaged in folding processes. The optimal model is established base on response surface methodology, which aimed at maximizing the strain energy and minimizing the peak moment to ensure full deployment stably. The failure index during folding processes are subjected (less than 1) to avoid material damage. The length of slot L, width of slot D, diameter R and thickness T of tube hinge are chosen as the design variables. Using the non-dominated sorting genetic algorithm, the optimum parameters are obtained by solving the multi-objective optimal model. The proposed method has significance on designing novel deployable structures with high stability and reliability.
Concurrent wind and base vibration energy harvesting with a broadband bistable aeroelastic energy harvester
Authors: Zhao Liya
Published: September 2019

This paper presents a novel energy harvesting device driven by concurrent aeroelastic vibration and base vibratory excitation. The harvester undergoes flow-induced limit-cycle oscillation under galloping instability, and at the same time, inertia force induced vibration is present due to the base vibratory excitation. A limitation with a traditional linear aeroelastic energy harvester is that effective energy harvesting from combined sources is only achievable within a narrow frequency range. To overcome this issue, bistability is introduced by exploiting nonlinear restoring force. A lumped aero-electro-mechanical model is established to incorporate the mutual coupling between the wind flow, piezoelectric element, nonlinear structure and circuit. Dynamic responses are investigated for different bistable configurations. Results show that the proposed harvester achieves a significantly widened bandwidth over which the two excitation frequencies are forced to lock into each other, and both vibratory and aeroelastic energy are effectively harnessed.
The lightweight topology optimization of plate/shell structures with different mechanical performance constraints
Authors: Wang W W , Ye H L , Sui Y K
Published: September 2019

The plate/shell structures are popular among in engineering because they show great potential in lightweight design under pressure loads. This paper develops a lightweight topology optimization method of plate/shell structures considering different mechanical performances based on independent, continuous and mapping (ICM) method. A mathematical formulation is established to describe the plate/shell topology optimization problem with minimum volume or mass as objective, the critical buckling load and nodal displacement as constraints. The finite element model is employed to subdivide the design domain and the existing state of each element is described as a topology design variable. In addition, linear buckling and static analyses are used to get the critical buckling load and nodal displacement of plate/shell structures and relevant information of elements and nodes used in the process of topology optimization. The filter functions are introduced to recognize element properties and map the 0-1 integer programming model into a formulation with continuous variables. Sensitivity analysis and Taylor expansion are applied to achieve a standard quadratic programming model. Finally, numerical examples are provided to test the effectiveness and feasibility of the theory above, and discuss the influence of constraints on optimal structures. This study can provide a theoretical basis for the lightweight topology optimization of plate/shell structures.
The Photoacoustic Effect of Multilayered Graphene Films
Authors: Yang Nizi , Li Shuang , Li Cheng , Fan Xueliang
Published: September 2019

This paper presents a theoretical model of the photoacoustic effect for mutilayered graphene films based on the photoacoustic theory of solids and the thermoacoustic theory of graphene films. The expression of sound pressure of the photoacoustic signal from a mutilayered graphene film is therefore derived according to the theoretical formula. An acoustic platform is built to measure the output sound pressure generated by graphene film on a polyethylene terephthalate (PET) substrate, and the experimental values are compared with the corresponding theoretical values. The results show that the trends of the two in the frequency domain are identical, thereby validating the proposed theoretical model. The graphene film speaker has a wide range of frequency response, and the output sound pressure of the film varies linearly with the input optical power. In the far-field region below 17000 Hz, the output sound pressure of the film gradually rises with an increase of the incident light frequency under constant incident light power. The frequency response of the film is relatively stable in the near-field region by comparison.
Linker length affects photostability of protein-targeted sensor of cellular microviscosity
Authors: Kubánková Markéta , Chambers Joseph E , Huber Roland G , Bond Peter J , Marciniak Stefan J , Kuimova Marina K
Published: September 2019

Viscosity sensitive fluorophores termed ‘molecular rotors’ represent a convenient and quantitative tool for measuring intracellular viscosity via Fluorescence Lifetime Imaging Microscopy (FLIM). We compare the FLIM performance of two BODIPY-based molecular rotors bound to HaloTag protein expressed in different subcellular locations. While both rotors are able to penetrate live cells and specifically label the desired intracellular location, we found that the rotor with a longer HaloTag protein recognition motif was significantly affected by photo-induced damage when bound to the HaloTag protein, while the other dye showed no changes upon irradiation. Molecular dynamics modelling indicates that the irradiation-induced electron transfer between the BODIPY moiety and the HaloTag protein is a plausible explanation for these photostability issues. Our results demonstrate that binding to the targeted protein may significantly alter the photophysical behaviour of a fluorescent probe and therefore its thorough characterisation in the protein bound form is essential prior to any in vitro and in cellulo applications.