Open Volume Research Articles

Modelling the primary damage in Fe and W: influence of the short-range interactions on the cascade properties: Part 2 – multivariate multiple linear regression analysis of displacement cascades

Neutrons and high energy ions create displacement cascades in materials, which have been simulated using Molecular Dynamics, for many decades now. The breakthrough of this work is to explore in a large statistics of more than 7000 cascades the relation between early cascade morphology and the final primary damage using a multivariate multiple regression analysis. For two energies in Fe and W, the total number of defects, the number of SIA and vacancy clusters and their full size distributions have been characterized using a multivariate multiple linear regression analysis based on 7 descriptors of the primary damage and 3 morphology descriptors. We find that the combination of the volume and the sphericity is significant. This analysis highlights several cascade properties, among them, that the large and spherical cascades create less defects and in particular, less mono defects than small and fragmented ones. 13 interatomic potentials differing either by their equilibrium part or the way they were hardened have been included in this study and the multivariate analysis shows that the choice of potential has a limited influence on the total number of defects but a large one on the number of mono vacancies. On average, soft potentials create cascades of larger volume, smaller sphericity and producing more defects than hard potentials. Finally, the formation of vacancy clusters is different in Fe than in W. In Fe, the fraction of vacancies in clusters is larger than that of SIAs and larger vacancy clusters are created than SIA clusters. In W, it is the opposite. The reasons are the differences of stopping power and threshold displacement energies, which result in different spatial distributions of open volumes that form during the expansion stage of the cascade.

Binary options trading: candlestick prediction using Support Vector Machine (SVM) on M5 time period

Many people choose to trade binary options because it is not difficult to understand. They need to predict whether the price will be higher or lower than their open position in a specific timeframe. The most popular timeframe for binary options traders is the M5 (5-minutes). Many traders prefer to use a candlestick chart model to predict. We use SVM (Support Vector Machine) to indicate the next-candlestick based on the previous-candlestick features in this research. This paper uses six features such as Open Value, Close Value, High Value, Low Value, Volume Value, and previous Candlestick Color on each candlestick. The result of the prediction accuracy using SVM is only 56%.

Surgeon Volume And Established Hospital Peri-operative Mortality Rate Together Predict Superior Outcomes After Open AAA Repair

ABSTRACT BACKGROUND In 2018, the SVS published hospital volume guidelines for elective open abdominal aortic aneurysm (AAA) repair, recommending elective open surgical repair for AAA be performed at centers with an annual volume of at least 10 open aortic operations of any type and a documented perioperative mortality of 5% or less. Recent work suggests a yearly surgeon volume of ≥7 open aortic cases for improved outcomes. The objective of this study is to assess the importance of hospital volume and surgeon volume at these cut points in predicting 1-year mortality after OSR for AAA. METHODS We evaluated patients undergoing elective open AAA repair using The New York Statewide Planning and Research Cooperative System database from 2003 to 2014. The effect of the SVS guidelines on postoperative mortality and complications was evaluated. Confounding between hospital and surgeon volume was identified using mixed-effects multivariate cox proportional hazards analysis. The effect of interactions between hospital volume, established hospital perioperative survival, and surgeon volume on post-operative outcomes was investigated. RESULTS The cohort consisted of 7,594 elective open AAA repairs performed by 542 surgeons in 137 hospitals over the 12 years. Analysis of the 2018 guidelines using the SPARCS database resulted in 1-year and 30-day mortality rates of 9.2% (8.3–10.1) and 3.5% (2.9-4.1) for centers that were within the guidelines and 13.6% (12.5–14.7) and 6.9% (6.1-7.8) for those that were outside the guidelines, respectively (both p CONCLUSIONS These data demonstrate centers that meet the SVS AAA volume guidelines are associated with improved 1-year and 30-day all-cause survival; however, are confounded by surgeon volume. Surgeon open aortic volume ≥7 and established hospital perioperative mortality of ≤5% each independently predict 1-year survival after open AAA repair, while hospital volume is less important. Surgeons with an annual volume of at least 7 open aortic operations of any type should perform elective open AAA repair at centers with a documented perioperative mortality of 5% or less.

Is Zygomatic Osteotomy a Viable Option to Achieve Symmetry and Stability in Post-traumatic Residual Deformity of the Zygomaticomaxillary Complex?

In residual deformity cases, it is difficult to reposition the zygomaticomaxillary-complex (ZMC) intraoperatively, due to resorbed fracture edges, and lack of zygoma analysis to 3-dimensionally quantify the deformity. Instability after zygomatic osteotomy and miniplate fixation (ZOMF) due to the gap between osteotomized segments, scar tissue, muscle pull, and other factors is also unknown. The study aims to evaluate symmetry and stability after ZOMF. In this prospective study, a ZMC analysis was designed and patients with unilateral post-traumatic residual deformity (>10weeks) of ZMC were treated with ZOMF. Measurements were evaluated on affected and unaffected sides at preoperatively, immediately, and 6months postoperatively using MIMICS software. The primary outcome variable was the symmetry and stability of ZMC. Secondary parameters were changes in orbital volume, diplopia, ocular motility, mouth opening, and patient satisfaction. P<.05 was considered statistically significant. The continuous variables were compared by paired t-test. The change within the continuous variable with time was assessed by repeated measure ANOVA, followed by multiple comparisons using the Bonferroni test. The changes within the categorical variable were assessed by the McNemar test. Ten patients were enrolled (mean age=29.2±9.97years; male:female=9:1; right:left=4:6). The mean duration from trauma to surgery was 34.84±31.35weeks. There was an improvement in the symmetry in anteroposteriorly (P=.005), mediolaterally (P=.001), and at the arch (P=.011) postoperatively. All parameters remained stable at 6months postoperatively (difference not significant, P>.05); with the median satisfaction score of 4 of 5. Significant improvement in mouth opening (P=.014) and orbital volume (P=.001) was noted. Virtual measurements as per the proposed protocol helped in communication and quantifying ZMC. Four-point fixation with miniplates provided enough stability over the 6-month follow-up period.

Identification of chemical surrounding and type of vacancy defects in the damaged region of ion irradiated Ni–Cr alloy

Identification of defects such as vacancy, ion-vacancy complex, vacancy clusters and voids etc. in the damaged region of ion-irradiated alloys is required to establish the structure–property relationship. Positron annihilation spectroscopy, due to very high propensity of positrons towards open volume defects, is extensively used to characterize the vacancy defects in the damaged region of ion irradiated alloys. However, in the absence of model calculations, experimental observations are qualitatively attributed to different possibility of defects in the damaged region. In the present study, positron lifetime and Doppler broadening calculations in different configurations of defects such as vacancy, vacancy cluster, ion-vacancy complex and implanted ions clusters have been performed in Ni–40% Cr alloy considering irradiation induced damage using H, He and Ar ions. The variations observed in positron lifetime and line shape parameters clearly show the effect of chemical surrounding and type of defects on positron annihilation characteristics. On comparison with experimental data, defect type and their chemical environment have been unequivocally identified in the damaged region of He ion-irradiated Ni–Cr alloy. The observed trends of positron annihilation characteristics could be applicable to a number of transition metal alloys for identification of ion-irradiation induced defects.

Operando Monitoring of Charging Processes in Battery Cathodes by Magnetometry and Positron Annihilation

Research in the field of modern battery materials demands characterization techniques which allow an inspection of atomistic processes during battery charging and discharging. Two powerful tools for this purpose are magnetometry and positron-electron annihilation. The magnetic moment serves as highly sensitive fingerprint for the oxidation state of the transition metal ions, thus enabling to identify the electrochemical ”active” ions. The positron lifetime on the other hand, is sensitive to open volume defects of the size of a few missing atoms down to single vacancies providing an unique insight into lattice defects induced by charging and discharging. An overview will be given on operando magnetometry studies of the important class of LiNiCoMn-oxide cathode materials (so-called NMC with Ni:Co:Mn ratios of 1:1:1 and 3:1:1) as well as of sodium vanadium phosphate cathodes. First operando positron annihilation studies on a battery cathode material (NMC 1:1:1) demonstrate the capability of this technique for battery research.

Preface

2020 International Conference on Defence Technology, Nanjing, China – Autumn Proceedings I am hugely delighted and excited to be writing this preface to the Autumn Proceedings of the 2020 International Conference on Defence Technology (ICDT). This is the second ICDT and is intended to be one in a long series of ICDT, taking place at intervals of approximately 18 months. The 2020 ICDT is co-chaired by Professor Changgen Feng and myself and supported by the China Ordnance Society.Due to circumstances beyond our control, the ICDT was postponed from 20-24 April to 26-30 October, 2020. We recognised it was important to many authors that their papers were published in April, as originally scheduled. Therefore, with the kind agreement of the publisher (Institute of Physics (IOP)), it was decided to publish the 2020 ICDT Proceedings in two editions, the first in Spring and the second in Autumn. The Spring edition is published and the papers are available at https://iopscience.iop.org/volume/1742-6596/1507.The ICDT provides an opportunity for scientists, engineers, and others to report, share and discuss current research and advances in defence technology and their visions for the future. The symposium allows exposure to the most current state-of-the-art technology in defence science, provides opportunities for interactions with some of the world’s leading experts in the field of defence science, and offers the chance to present, exhibit, and share scientific research and development with an international group of professionals.A wide range of papers is encouraged at the ICDT, from work in progress through to high quality scientific papers. These papers comprise an extensive range of defence science and technology areas covered by the symposium: energetic materials, explosion & impact, armour & protection, novel manufacturing processes, autonomous technology, application of composite materials, directed energy & pulsed laser, modelling & simulation, and photoelectronic information technology.This is the first ICDT Proceedings to be published by IOP Publishing Ltd as an open access volume of the Journal of Physics: Conference Series. The Proceedings were enabled by the good cooperation between the ICDT and Defence Technology journal, which is sponsored by the China Ordnance Society and published by KeAi Publishing Communications Ltd. I would like to thank the China Ordnance Society, the Editors and the Editorial Office, Ms. LI Ying, Ms. MA Xin, Ms. MA Yanhong and Ms. Liu Li for their dedicated, hard and expeditious work in producing this issue. I also thank the technical reviewers of the papers contained in these Proceedings and the sponsors of the ICDT who have helped to make the ICDT possible.I hope you will find these Autumn Proceedings stimulating and very interesting. ICDT provides an opportunity to develop an understanding of the entire realm of defence science and technology outside of the reader’s specialist area. I therefore highly commend these Autumn Proceedings to you.Clive Woodley, 2020 ICDT co-chair.Institute of Shock Physics, Imperial College, London, UK.Changgen FengBeijing Institute of Technology, ChinaBaoming LiNanjing University of Science and Technology, China Academy of Ordnance Science, China

Laparoscopic Hepatic Lobectomy for Symptomatic Polycystic Liver Disease

Introduction: Laparoscopic fenestration has largely replaced open fenestration of liver cysts. However, most hepatectomies for polycystic liver disease (PCLD) are performed open. Data on laparoscopic hepatectomy for PCLD is lacking. We present a series of patients who underwent laparoscopic hepatectomy for symptomatic PCLD. Methods: A retrospective review of patients who underwent surgery for PCLD at a single institution between 2010 and 2019 was performed. Patients were grouped based on operative approach. Pre- and post-operative volumes were calculated for patients who underwent resection. The primary outcomes were: volume reduction, re-admission and postoperative complications. Results: Twenty-six patients were treated for PCLD: 13 (50%) with laparoscopic fenestration, nine (34.6%) with laparoscopic formal hepatectomy, three (11.5%) with open formal hepatectomy and one (3.8%) with liver transplantation. Average length of stay for the patients who underwent laparoscopic resection was 3 days (IQR 2-3.5), with no readmissions. One patient developed postoperative atrial fibrillation. There were no other complications. Overall volume reduction was 51.4% (22.3-68.5), 32.2% (range 22.3-46.7) after open resection and 56% (range 38.8-68.5) after laparoscopic resection. Average length of follow-up for the patients who underwent laparoscopic resection was 26 months (IQR 4-102). Conclusion: Performing hepatectomy for PCLD is challenging as anatomic planes and vasculature are distorted. The laparoscopic approach even more so due to limited working domain from hepatomegaly. Volume reduction achieved through laparoscopic approach is comparable to volume reduction in previously published open resection series, and exceeded open volume reduction at our institution. Adequate volume reduction can be accomplished by laparoscopic means with acceptable postoperative morbidity.

Contrast-Free Detection of Focused Ultrasound-Induced Blood-Brain Barrier Opening Using Diffusion Tensor Imaging.

Focused ultrasound (FUS) has emerged as a non-invasive technique to locally and reversibly disrupt the blood-brain barrier (BBB). Here, we investigate the use of diffusion tensor imaging (DTI) as a means of detecting FUS-induced BBB opening at the absence of an MRI contrast agent. A non-human primate (NHP) was repeatedly treated with FUS and preformed circulating microbubbles to transiently disrupt the BBB (n = 4). T1- and diffusion-weighted MRI scans were acquired after the ultrasound treatment, with and without gadolinium-based contrast agent, respectively. Both scans were registered with a high-resolution T1-weighted scan of the NHP to investigate signal correlations. DTI detected an increase in fractional anisotropy from 0.21 ± 0.02 to 0.38 ± 0.03 (82.6 ± 5.2% change) within the targeted area one hour after BBB opening. Enhanced DTI contrast overlapped by 77.22 ± 9.2% with hyper-intense areas of gadolinium-enhanced T1-weighted scans, indicating diffusion anisotropy enhancement only within the BBB opening volume. Diffusion was highly anisotropic and unidirectional within the treated brain region, as indicated by the direction of the principal diffusion eigenvectors. Polar and azimuthal angle ranges decreased by 35.6% and 82.4%, respectively, following BBB opening. Evaluation of the detection methodology on a second NHP (n = 1) confirmed the across-animal feasibility of the technique. In conclusion, DTI may be used as a contrast-free MR imaging modality in lieu of contrast-enhanced T1 mapping for detecting BBB opening during focused-ultrasound treatment or evaluating BBB integrity in brain-related pathologies.

Defect characterization of damaged region of carbon implanted alumina: Effect of ion fluence and annealing

Alumina is considered as a promising host for production of embedded nanoclusters through ion implantation methods. Alumina is also being proposed to be a structural material as an isolating ceramics for thermo-nuclear fusion reactors wherein it will be exposed to high energy radiation. In addition, C-doped alumina is being proposed for medical dosimetery. In order to use alumina for all these applications, a better understanding of defects evolutions at atomic level is required. For this purpose, in the present study, α-alumina crystals have been implanted with C ions (50 keV) with total fluence of 1 × 1015, 5 × 1015, 1 × 1016 and 1 × 1017 ions/cm2 at room temperature. The ion implanted samples have been annealed at 500 °C for 2 h in ambient atmosphere. The ion implantation profile and vacancy distribution profiles have been calculated using computer code SRIM. Depth dependent defect distributions in ion implanted and annealed samples have been experimentally determined using depth dependent Doppler broadening spectroscopy. The experimental data have been analyzed using computer code VEPFIT. The S-E profiles of ion implanted samples confirm that Al vacancy and C ion-vacancy complexes are the primary defects produced due to ion implantation. At the highest implanted dose, amorphization of damaged region is observed. On thermal annealing, samples with lower fluence (1 × 1015 and 5 × 1015 ions/cm2) are recovered followed by annealing out of defects. On the other hand, samples with higher fluence (1 × 1016 and 1 × 1017 ions/cm2) indicate the formation of open volume defects such as vacancy clusters or voids which is confirmed through S-W correlation plots.

Mesoscale simulation of pull-out performance for corroded reinforcement with stirrup confinement in concrete by 3D RBSM

The confining effect of concrete cover and stirrups reduces the rate of bond deterioration due to corrosion. However, the large dispersion in recorded experimental data makes it difficult to clearly separate the influence of cover depth and stirrup confinement on bond degradation. This study utilises the discrete 3D Rigid Body Spring Model (RBSM) to conduct a meso-scale investigation regarding the effect of cover thickness and stirrup confinement on internal crack evolution and pull-out behaviour in corroded reinforced concrete models. The simulation scheme is divided into two stages. In stage 1, different degrees of corrosion are introduced, producing cracking in the cover concrete; in stage 2, the corroded main reinforcement is pulled out from the damaged concrete. 3D RBSM is advantageous because the concrete is randomly meshed to reduce mesh bias on crack propagation and the actual geometry of the deformed bars is modelled. The simulation results clarify that the presence of thicker cover delays crack initiation but increases the rate of crack opening. Stirrups do not have any significant effect on crack initiation but effectively restrict crack growth. An investigation of the internal stress in the simulation models shows that tensile stresses generated in stirrups during corrosion are responsible for reactionary confining pressure that restricts crack propagation. Load-displacement curves show reductions in pull-out capacity, stiffness and ductility with increasing corrosion damage. The relative influence of crack opening and stirrup volume on the rate of bond degradation with respect to average surface crack width are discussed and compared with published experimental results and an empirical equation.

Predictive control model for variable air volume terminal valve opening based on backpropagation neural network

To determine the valve opening for controlling air volume, the relationship among valve opening, static pressure and air volume is studied through experiment. A prediction model for valve opening based on back propagation neural network is proposed. Firstly, the appropriate number of hidden layers and neurons is determined by calculating the error of test set and training set. Secondly, the prediction effect of the model is tested under different conditions. The test result shows that the error between the predicted result and the expected result is less than 5%. Thirdly, the prediction results of the neural network model and the quadratic function model have high consistency. In contrast, neural networks have stronger nonlinear fitting capabilities and are more suitable for solving complex problems. Additionally, compared with the traditional feedback adjustment method, the approximation ability of the neural network model can be used to directly output the position of the VAV terminal demand valve, thus reducing the convergence time and stabilization time, and improving the energy-saving effect and indoor environment comfort. The proposed model can provide reference for the design and debugging of related air supply terminal products, not limited to ship VAV terminal.

A CNN-LSTM-Based Model to Forecast Stock Prices

Stock price data have the characteristics of time series. At the same time, based on machine learning long short-term memory (LSTM) which has the advantages of analyzing relationships among time series data through its memory function, we propose a forecasting method of stock price based on CNN-LSTM. In the meanwhile, we use MLP, CNN, RNN, LSTM, CNN-RNN, and other forecasting models to predict the stock price one by one. Moreover, the forecasting results of these models are analyzed and compared. The data utilized in this research concern the daily stock prices from July 1, 1991, to August 31, 2020, including 7127 trading days. In terms of historical data, we choose eight features, including opening price, highest price, lowest price, closing price, volume, turnover, ups and downs, and change. Firstly, we adopt CNN to efficiently extract features from the data, which are the items of the previous 10 days. And then, we adopt LSTM to predict the stock price with the extracted feature data. According to the experimental results, the CNN-LSTM can provide a reliable stock price forecasting with the highest prediction accuracy. This forecasting method not only provides a new research idea for stock price forecasting but also provides practical experience for scholars to study financial time series data.

Oxidation of amorphous HfNbTaTiZr high entropy alloy thin films prepared by DC magnetron sputtering

High entropy alloys represent a new type of materials with a unique combination of physical properties originating from the occurrence of single-phase solid solutions of numerous elements. The preparation of nanostructured or amorphous structure in a form of thin films promises increased effective surface and high intergranular diffusion of elements as well as a high affinity to oxidation. In this work, we studied HfNbTaTiZr thin films, deposited at room temperature by DC magnetron sputtering from a single bcc phase target. Films exhibit cellular structure (∼100 nm) with fine substructure (∼10 nm) made of round-shape amorphous clusters. The composition is close to equimolar with slight Ti enrichment and without any mutual segregation of elements. Oxidation at the ambient atmosphere leads to the formation of Ti, Zr, Nb, Hf, and Ta oxide clusters in the film up to the depth of 200–350 nm out of the total film thickness of 1650 nm. Oxygen absorption takes place preferentially in the large vacancy clusters located in between the amorphous cluster aggregates. The dominant type of defect are small open volumes with a size comparable with vacancy. The distribution of these defects is uniform with depth and is not influenced by the presence of oxygen in the film.

Densification behaviour and three-dimensional printing of Y2O3 ceramic powder by selective laser sintering

The selective laser sintering (SLS) of an yttria (Y2O3) ceramic powder was studied to understand both the effects of i) the initial yttria particle characteristics on the powder bed behaviour and ii) the process conditions (laser power, scanning speed, hatching space) on the sintering/melting of three-dimensionally printed objects. The roughness of the powder bed, a sensitive indicator of the layer bed quality, was determined through three-dimensional optical profilometry and the powder bed packing density was modelled using the discrete-element method. Complex shaped objects including spheres and open rings were successfully fabricated by the SLS three-dimensional printing. In addition, SLS cube-shaped samples were characterized by X-ray diffraction and scanning electron microscopy. The open pore volume fraction significantly decreased from 41% without a post-SLS heat treatment to 31% with a post-SLS heat treatment at 1750 °C for 20 h under secondary vacuum. Finally, an anisotropy in elastic properties has been highlighted, Young's modulus reaches 11 GPa in the stiffest direction.

Production Conditions of Nanoporous Ceramics Based on Mullite

A technology for producing nanoporous ceramics based on mullite (3Al2O3 ⋅ 2SiO2) is developed. The mechanochemical activation of oxides involved in the synthesis of mullite (γ-Al2O3 and amorphous SiO2) makes it possible to obtain single-phase 3Al2O3 ⋅ 2SiO2 and to reduce its sintering temperature to 1300°С. The effect of the pressing pressure and the amount of pore-forming additive (ammonium carbonate) on the value of open porosity, pore volume, and pore size distribution in sintered ceramics 3Al2O3 ⋅ 2SiO2 is established. Mullite nanoceramics with open porosity of 42–47%, pore size <200 nm, and compressive strength 50–65 MPa is obtained.

Breaking the Ice: Identifying Hydraulically Forced Crevassing

AbstractHydraulically forced crevassing is thought to reduce the stability of ice shelves and ice sheets, affecting structural integrity and providing pathways for surface meltwater to the bed. It can cause ice shelves to collapse and ice sheets to accelerate into the ocean. However, direct observations of the hydraulically forced crevassing process remain elusive. Here we report a novel method and observations that use icequakes to directly observe crevassing and determine the role of hydrofracture. Crevasse icequake depths from seismic observations are compared to a theoretically derived maximum dry crevasse depth. We observe icequakes below this depth, suggesting hydrofracture. Furthermore, icequake source mechanisms provide insight into the fracture process, with predominantly opening cracks observed, which have opening volumes of hundredths of a cubic meter. Our method and findings provide a framework for studying a critical process that is key for the stability of ice shelves and ice sheets and, therefore, future sea level rise projections.

Study of fly ash based zeolite by using slow positrons

After coal fly ash activation with alkaline NaOH solution by the hydrothermal method, it was possible to synthesize the zeolites type Cancrinite and Analcime. Slow positron beam experiments have been performed on two set of samples. One in which the NaOH concentration was varied and another one in which the synthesis temperature range was varied. The mineralogical composition was determined by X ray diffraction, the morphology of one of the zeolite samples as compared with the coal fly ash was observed by 3D X-ray imaging. Positron results suggest that increasing the NaOH concentration produces an increase in open volume and/or defects while increasing the temperature in the sample preparation diminishes it.

Application of the reciprocity theorem to scattering of surface waves by an inclined subsurface crack

In this paper the scattering of incident surface waves by an inclined subsurface crack in a homogenous, isotropic and linearly elastic half-space has been investigated in a two-dimensional plane strain configuration. The elastodynamic reciprocity theorem together with a virtual wave has been used to determine the amplitude of the scattered surface waves in the far field. It is found that the amplitude is in terms of the crack opening volume due to the incident surface waves. A special case of low frequency, for which the wavelength of the surface wave is sufficiently larger than the crack length, has been considered to illustrate the method. A specific expression of the amplitude has been obtained, which provides information on the angle, length and depth of the crack. It shows that the amplitude of the scattered surface wave increases first and then decreases as the crack angle changes from 0° to 90°. For the case of an inclined crack, the results of the numerical analysis together with the analytical solutions show excellent agreement when the crack length is much smaller than the wavelength. The results in this paper should be useful for the quantitative measurement of subsurface cracks.

Structural Changes and Electrodynamic Effects in Polymers under Fast Uniaxial Compression

Rheological explosion in polymers under uniaxial compression in an open volume occurs at the end of continuous rapid plastic deformation after several stages of creep. Two types of polymers were chosen for this study: brittle glassy amorphous polystyrene and thermoplastic semi-crystalline polypropylene. Electric pulses were detected during explosion, and their spectra were analyzed with two models. X-ray diffraction methods were used to investigate changes in the structure and morphology of polymers during deformation and rheological explosion. The pores appear in polymer in this process, and their shape and size distribution were derived from X-ray experiments. The main reason for the formation of pores in polymer samples in rheological explosion experiments is the intense microshifts in the polymer volume under the action of high applied pressure.