bluuebunny/crossref_metadata_2025 huggingface dataset:
Average carbon content change during gas-solid decarburization of 2 mm iron sheet with a high carbon content
Authors: Cheng Rong , Ai Liqun , Hong Lu-kuo , Sun Cai-jiao
Published: January 2020

The average carbon content after decarburization is an important criterion in judging the feasibility of the solid-state steelmaking process. To investigate the change mechanism of the average carbon content, the gas-solid decarburization of 2 mm iron sheet in weak oxidizing atmosphere (Ar + H2 + H2O) at 1293, 1353, and 1413 K is studied. The influences of decarburization time and temperature are considered. Increasing both the temperature and time can enhance decarburization. The gas-solid decarburization reaction of 2 mm iron sheets is nearly a first-order reaction, and the activation energy of the decarburization reaction is 144.9 kJ/mol. It was found that the diffusion of carbon from the interior of the sheet to the reaction interface is the rate-controlling step. The relationship between decarburization time, temperature, and average carbon content is precisely described by an empirical formula. A new segmented heating method is developed. With this new method, 0.28 mass% C sheets can be produced from 4.15 mass% C sheets with thickness of 2 mm in 70 min.
Problems of transformation in the tourism industry in the digital economy
Authors: Bozhuk Svetlana , Pletneva Natalya , Maslova Tatiana , Evdokimov Konstantin
Published: January 2020

The article is devoted to researching of current conditions of the tourism industry from consumers behavior position. In this work, the consumer is considered a legitimate participant in the creation of a tourist product. The aim of the work is to identify the impact of digital technology on the transformation of the decision-making process by tourists. The tasks are to assess the state of the digital tourism infrastructure, classify the available services to identify unfilled niches; to find out the attitude of consumers to various kinds of travel applications and their place in travel planning. The empirical basis of the work has been the research data by Google, PayPal, Booking.com which allowed to analyze tourists’ behavior in the Internet and to identify the main travel trends for 2019. For achieve the research aim, authors applied an online survey of 100 consumers aged 18-35 too. As a result, the main directions of tourism transformation in the digital economy were determine and classification of applications in the category of "travel" were created.
US-China Trade War: Causes and Outcomes
Authors: Kapustina Larisa , Lipková Ľudmila , Silin Yakov , Drevalev Andrei
Published: January 2020

The article reviews the chronology and analyses the causes and possible consequences of the trade war between the US and China. The authors identify four main reasons that led to the greatest trade conflict between the two economies in history associated with intentions of the US: a) to reduce the deficit of bilateral trade and increase the number of jobs; b) to limit access of Chinese companies to American technologies and prevent digital modernization of the industry in the PRC; c) to prevent the growth of China’s military strength; and d) to reduce the federal budget deficit. It is confirmed and concluded that trade wars have no winners. Taking into account the two countries’ GDP scale and export volumes, the US-China trade war will come amid a slowdown in the global production and international trade. The article analyses the outcomes of the trade confrontation based on the scenario methodology. The authors identify 4 scenarios by making assumptions about the response pattern and conjectural variation in the bilateral economic relations. The US protectionist policy has its political dimension. The constraints of the bilateral trade is one of the tools for slowing China's military and economic power growth.
Machine learning forecasting of CR import from PRC in context of mutual PRC and USA sanctions
Authors: Machová Veronika , Mareček Jan
Published: January 2020

Mutual trade restrictions between the USA and the PRC caused by the USA feeling of imbalance of trade between these two countries have significantly influenced not only the trade between these two states but also the overall atmosphere of the international trade in the last few years. The objective of the contribution is to find out whether machine learning forecasting is capable of equalizing time series so that the model effectively forecasts the future development of the time series even in the context of an extraordinary situation caused by such factors as the mutual sanctions of the USA and PRC. The dataset shows the course of the time series at monthly intervals starting from January 2000 to June 2019. There is regression carried out using neural structures. Three sets of artificial neural networks are generated. They are differ in the considered time series lag. 10,000 neural networks are generated, out of which 5 with the best characteristics are retained. The mutual USA and PRC sanctions did not affect the success rate of the machine learning forecasting of the CR import from the PRC. It is evident that the mutual sanctions shall affect the trade between the CR and the PRC.
Anti-crisis approach in the industrial enterprise management: methodological tools of preventive regulation
Authors: Maslak Olga , Sokurenko Petro , Grishko Natalya , Buriak Ievgen , Maslak Mariya
Published: January 2020

The paper covers the theoretical and methodological framework for assessment of the crisis management effectiveness and the enterprise bankruptcy probability. At the present stage of the Ukrainian economic development, the main weaknesses in the activities of enterprises include: loss of sales markets, imperfect production and sales policy, lack of working capital, inefficient financial management, significant production costs, which produce signs of crisis processes and determine the feasibility of preventive approach anti-crisis management use. At the same time, the choice of the topic is due to insufficient research of this scientific problem as a whole and its relevance for the economy of Ukraine, especially in the context of the search for external investment resources, cooperation on this basis with the European Union.

It was determined that one of the ways to solve the problem of predicting the probability of bankruptcy is the use of insolvency prediction models developed on the basis of the discriminant analysis method – Z-coefficients. The authors systematized the most well-known approaches to predicting the likelihood of bankruptcy of industrial enterprises, illustrated their advantages and disadvantages, the mutual consistency of use.

It has been established that additional opportunities for monitoring the effectiveness of anti-crisis measures are created by a system of indicators characterizing the level of effectiveness of the anti-crisis management system. Evaluating the effectiveness of the anti-crisis program only on the basis of an analysis of relative indicators is not enough: during the global financial crisis, sometimes convincing indicators of efficiency are absolute indicators and a projected trend of their change.

As part of this study, attention is paid to the analytical levers of the crisis management mechanism, which are aimed at preventive regulation and localization of crisis processes in the enterprise, restoring the effectiveness of production and marketing activities.
Evaluation of the EU Policy Concerning the Basic Economic Functions of a Modern Government in a Mixed Economy
Authors: Rousek Pavel
Published: January 2020

The paper analyses the budget of the European Union in terms of its redistribution power and stabilization efficiency. The redistribution of finance from rich regions to poorer ones is an important function of public budgets. The EU budget only partially fulfils this function. Stabilizing economic development is another important function of public budgets. Also, the effectiveness of the EU budget in this area is not sufficient and could be significantly strengthened.
Strategic Management and Decision Making of Small and Medium-Sized Enterprises in the Czech Republic
Authors: Straková Jarmila , Talíř Milan
Published: January 2020

The topic of strategic management and decision making was underestimated by SMEs for a long term. Managers believed that experience, intuition and operability are the key success factors of their management work. These opinions have recently been abandoned in the management practice. This paper is focused on the analysis of strategic management and decision making and presents the outputs from research based on a test sample of 381 enterprises, of which 114 microenterprises, 141 small enterprises and 126 medium-sized enterprises. The company size categorization within this sample is corresponding to the SME structure in the South Bohemian Region. Lack of awareness of procedures for development of essential strategic documents such as vision, mission statements and a corporate strategy was observed. More than 60 % SMEs do not have such documents. are Similar results were obtained with respect to the development of a corporate strategy using the methods of a strategic situation analysis. This finding is alarming and its adverse impact can primarily be expected in a period of economic recession or downturn.
Management of hepatic encephalopathy in Germany: a survey among physicians
Authors: Labenz Christian , Adarkwah Charles C. , Wörns Marcus-Alexander , Miehlke Stephan , Hofmann Wolf P. , Buggisch Peter , Galle Peter R. , Frieling Thomas , Labenz Joachim
Published: January 2020

Background Hepatic encephalopathy (HE) is a severe complication of liver cirrhosis with impairment of quality of life and prognosis. Management patterns among physicians have not been investigated yet.

Methods A questionnaire containing 17 questions was sent out to 1468 gastroenterologists and 120 general practitioners (GPs). It included questions regarding diagnostic, therapeutic, and management strategies used in patients with overt HE (OHE) and covert HE (CHE).

Results The response rate was 12 % (n = 172) for gastroenterologists and 45 % (n = 54) for GPs. Of gastroenterologists, 26.7 % examine patients with an initial diagnosis of liver cirrhosis regarding HE. Gastroenterologists favored a combination of different testing strategies (27.9 %) and clinical examination (23.0 %), while the biggest part of the GPs use clinical examination (55.3 %); 63.7 % of gastroenterologists and 28.3 % of GPs give correct nutritional advices to patients with HE. Treatment strategies for acute bouts of OHE and secondary prophylaxis varied widely in both groups. Preferred medication was lactulose followed by rifaximin or a combination therapy. More than half of the GPs (53.7 %) were not familiar with minimal HE (MHE). About one-third of both groups never tried to diagnose MHE.

Conclusion Our data strongly indicate that management of HE is very heterogeneous among gastroenterologists as well as selected GPs working in Germany and not driven by evidence-based international guidelines. Thus, the national guideline is more than welcome.
STudy on E-Cigarettes and Pregnancy (STEP) – Study Protocol of a Mixed Methods Study on Risk Perception of E-Cigarette Use During Pregnancy and Sample Description
Authors: Schilling Laura , Schneider Sven , Maul Holger , Spallek Jacob
Published: January 2020

Introduction During pregnancy, the motherʼs healthy lifestyle is crucial for the health of the fetus. Potential risk factors for maternal and child health should therefore be identified and reduced as early as possible. The consumption of e-cigarettes represents one of these potential risk factors. Exploring risk perceptions about e-cigarette use during pregnancy can provide early indications of possible user motives. Therefore, our mixed methods STudy on E-cigarettes and Pregnancy (STEP) aimed to comprehensively analyze risk perceptions about e-cigarette use during pregnancy based on an Integrated Health Belief Model (IHBM). This paper describes the study design, methods, sample population and limitations of STEP.

Methods Our sequential mixed methods study combined qualitative and quantitative approaches. In the qualitative section of the study which preceded the quantitative part of the study, we aimed to characterize risk perceptions about e-cigarette use during pregnancy. We used a netnographic research approach which analyzed discussion threads in online forums dealing with e-cigarette use during pregnancy. The analysis was based on an IHBM. Identified themes were incorporated in the questionnaire which was developed for the quantitative part of the study. The quantitative section aimed to quantify, among other things, perceived threats, barriers and benefits and to explore differences in risk perception according to sociodemographic characteristics and tobacco and e-cigarette usage.

Results In the qualitative section, 1552 posts in 25 online discussion threads dealing, inter alia, with e-cigarette use during pregnancy were identified. The quantitative part looked at the responses in the questionnaires handed in by 575 pregnant women who attended a hospital in Hamburg (Germany) from April 2018 to January 2019 (response rate: 27.5%).

Conclusion Data collection was successful for both the qualitative and quantitative parts of the study. When interpreting the results of STEP, different limitations should be taken into account. The results of STEP provide starting points for the development of tailored preventive measures for pregnant women.
A Review: Prevention, Treatment and Management of Tuberculosis through Combinational Approaches of Different Indian Systems of Medicine
Authors: Sharma Priyanka , Goyal Ramesh K. , Nandave Mukesh
Published: January 2020

Tuberculosis (TB) is one of the oldest fatal diseases of history. Multidrugresistant tuberculosis (MDRTB) is a major public health issue in the world. In India, the incidence is getting up despite the Indian revised National Tuberculosis Control Programme. India has six recognize medicine systems in this category, namely Ayurveda, Siddha, Unani and Yoga, Naturopathy and Homoeopathy. This review study was undertaken to evaluate the efficacy of different drug treatments based on Indian Systems of Traditional Medicines to the standard MDR-TB regimen. This review mainly focuses on the combinational approaches towards treatment protocols, prevention strategies, and management of tuberculosis in different established systems of medicine in India. Along with allopathic drugs, these AYUSH based drugs work in synergistic manner. Recent research suggests that Homeopathic treatment along with the antibiotics synergise the effect of antibiotics while reaching to its site of action. Additionally in Siddha system, formulation of medicinal herbs showing significant activity against TB bacteria. Furthermore, adopting the management or principles of Unani system would be beneficial in health and disease. Similarly, Unani and Naturopathy through natural healing are equally effective. On the other hand, medicinal plants from the Ayurveda that have been successfully employed to treat TB because of less toxicity and side effect in comparison with existing antibiotics. The findings in this review have provided scientific support for anti-TB activity of different medicinal system of India via numerous underlying mechanisms.
Umpolung of Enamines: An Overview on Strategies and Synthons
Authors: Sukhorukov Alexey Yu.
Published: January 2020

Umpolung strategies are of considerable interest to organic chemists because they provide alternative synthetic routes to those imposed by the natural polarity of classical synthons. Reverse-polarity reactions of aldehydes, α,β-unsaturated carbonyl compounds, and imines are deeply embedded in the methodology of organic synthesis. In recent years, umpolung of enols and enamines has received much attention as a novel strategy to access α-substituted ketones. Here, state-of-the-art approaches to umpolung of enamine reactivity are discussed, with a particular focus on recent developments in this field from the author’s research group.

1 Introduction

2 Approaches toward Umpolung of Enamines

3 Umpolung of Enamines through Single-Electron Oxidation

4 Azadienes as Synthetic Equivalents of Enamine Umpolung Synthons

5 Enamines Possessing a Leaving Group at the Nitrogen Atom

6 Enamines Possessing a Directing Group at the Nitrogen Atom

7 Summary and Outlook
Transposition of Aromaticity from a Furan to a Cyclohexane Ring in Furoisoindoles During the Interaction of 3-(Furyl)allylamines with Bromomaleic Anhydride
Authors: Alekseeva Kseniia A. , Kvyatkovskaya Elizaveta A. , Nikitina Eugeniya V. , Zaytsev Vladimir P. , Eroshkina Svetlana M. , Shikhaliev Khidmet S. , Truong Hieu H. , Khrustalev Victor N. , Zubkov Fedor I.
Published: January 2020

An unexpected four-step reaction sequence was discovered in the course of investigation of the interaction between 3-(furan-2-yl)allylamines and bromomaleic anhydride. This conversion begins with the initial N-acylation of the allylamines by the anhydride, followed by intramolecular Diels–Alder reaction, which is accompanied by a dehydrohalogenation, and ends with the formation of partially unsaturated furo[2,3-f]isoindoles followed by transposition of aromaticity from the furan moiety to the neighboring cyclohexane ring. The reaction between 3-(furan-3-yl)allylamines and bromomaleic anhydride does not stop at a furo[2,3-f]isoindole formation step, but proceeds further with the cleavage of the furan ring in a 100% atom-efficient fashion to provide polysubstituted isoindoline-4-carboxylic acids.
Synthesis and Structural Diversity of Triaryl(phenylethyl)silanes
Authors: Linnemannstöns Marvin , Neumann Beate , Stammler Hans-Georg , Mitzel Norbert W.
Published: January 2020

Starting from trichloro(phenylethyl)silane, six differently fluorinated triaryl(phenylethyl)silanes were synthesized by salt elimination reactions and their structures were determined by X-ray diffraction analysis. Tris(pentafluorophenyl)(phenylethyl)silane reveals a folded structure due to intramolecular π-stacking interactions, while those with a lower degree of fluorination show either intermolecular π-stacking or no interplay between the aryl groups. A similar folded structure was observed for (4-methylphenethyl)tris(pentafluorophenyl)silane and [2-(naphth-2-yl)ethyl]tris(pentafluorophenyl)silane, both generated from the corresponding trichlorosilanes. In contrast, the inversely fluorinated [2-(pentafluorophenyl)ethyl]triphenylsilane only revealed intermolecular π-stacking interactions. Compounds with tetrafluoropyridyl substituents behave differently; with these compounds, π-stacking is only observed between the fluorinated units. All compounds were analyzed by NMR and IR spectroscopy, elemental analyses and single-crystal X-ray diffraction, and found to have strong H/C/N/F···F and N···C contacts.
Otoprotection Mechanisms Against Oxidative Stress Caused by Cisplatin
Authors: Gonçalves Maiara Santos , Silveira Aron Ferreira da , Murashima Adriana de Andrade Batista , Rossato Maria , Hippolito Miguel Angelo
Published: January 2020

Introduction Cisplatin damages the auditory system and is related to the generation of free radicals. Glutathione peroxidase is an endogenous free radicals remover.

Objective To investigate the mechanisms involved in otoprotection by N-acetylcysteine through the expression of glutathione peroxidase in outer hair cells from rats treated with cisplatin.

Methods Male Wistar rats were intraperitoneally injected with cisplatin (8 mg/Kg) and/or received oral administration by gavage of N-acetylcysteine (300 mg/Kg) for 3 consecutive days. On the 4th day, the animals were euthanized and beheaded. The tympanic bullae were removed and prepared for scanning electron microscopy and immunofluorescence.

Results Among the groups exposed to ototoxic doses of cisplatin, there was an increase in glutathione peroxidase immunostaining in two groups, the one exposed to cisplatin alone, and the group exposed to both cisplatin and N-acetylcysteine.

Conclusion The expression of glutathione peroxidase in the outer hair cells of rats exposed to cisplatin showed the synthesis of this enzyme under cellular toxicity conditions.
Causal network discovery by iterative conditioning: Comparison of algorithms
Authors: Kořenek Jakub , Hlinka Jaroslav
Published: January 2020

Estimating causal interactions in complex dynamical systems is an important problem encountered in many fields of current science. While a theoretical solution for detecting the causal interactions has been previously formulated in the framework of prediction improvement, it generally requires the computation of high-dimensional information functionals—a situation invoking the curse of dimensionality with increasing network size. Recently, several methods have been proposed to alleviate this problem, based on iterative procedures for the assessment of conditional (in)dependences. In the current work, we bring a comparison of several such prominent approaches. This is done both by theoretical comparison of the algorithms using a formulation in a common framework and by numerical simulations including realistic complex coupling patterns. The theoretical analysis highlights the key similarities and differences between the algorithms, hinting on their comparative strengths and weaknesses. The method assumptions and specific properties such as false positive control and order-dependence are discussed. Numerical simulations suggest that while the accuracy of most of the algorithms is almost indistinguishable, there are substantial differences in their computational demands, ranging theoretically from polynomial to exponential complexity and leading to substantial differences in computation time in realistic scenarios depending on the density and size of networks. Based on the analysis of the algorithms and numerical simulations, we propose a hybrid approach providing competitive accuracy with improved computational efficiency.
Survey of signal clamping for digital phase sensitive detector
Authors: Cui Ziqiang , Hu Yafeng , Wang Huaxiang
Published: January 2020

Electrical capacitance tomography (ECT) is a multiphase flow detection technology, which has the advantages of nonradioactive, noninvasive, and on-line visualization measurements. In ECT measurements, the digital phase sensitive demodulation (PSD) plays an important role in guaranteeing the accuracy of small capacitance measurements. Generally, the clamping circuit is implemented to protect the A/D converter. In the measuring circuit, a programmable gain amplifier is usually employed to expand the dynamic range of PSD. However, the measured signal may exceed the measurement range from time to time, which induces the signal clamping effect. In this case, the digital PSD will present large errors in the capacitance measurements. In consideration of the frequency spectrum characteristic of the clamped signal, two digital PSD methods have been proposed. The proposed methods have been implemented in a field programmable gate array based measurement system. The experimental results show that the proposed multisine PSD method could expand the dynamic range by a factor of 5, at a relatively low error, i.e., ≤2%.
Ultra-high mechanical flexibility of 2D silicon telluride
Authors: Bhattarai Romakanta , Shen Xiao
Published: January 2020

Silicon telluride (Si2Te3) is a two-dimensional material with a unique variable structure where the silicon atoms form Si-Si dimers to fill the “metal” sites between the Te layers. The Si-Si dimers have four possible orientations: three in-plane and one out-of-the plane directions. The structural variability of Si2Te3 allows unusual properties, especially the mechanical properties. Using results from first-principles calculations, we show that the Si2Te3 monolayer can sustain a uniaxial tensile strain up to 38%, the highest among all two-dimensional materials reported. The high mechanical flexibility allows applying mechanical strain to reduce the bandgap by 1.5 eV. With increasing strain, the bandgap undergoes an unusual indirect-direct-indirect-direct transition. We also show that the uniaxial strain can effectively control the Si-Si dimer alignment, which is beneficial for practical applications.
Precise absolute Seebeck coefficient measurement and uncertainty analysis using high-Tc superconductors as a reference
Authors: Amagai Y. , Shimazaki T. , Okawa K. , Kawae T. , Fujiki H. , Kaneko N.-H.
Published: January 2020

The intrinsic properties of superconductors enable the direct determination of the absolute Seebeck coefficient at low temperature due to the disappearance of the Seebeck effect to obey the Meissner effect. We report a precision absolute Seebeck coefficient measurement for the fine Pt sample determined using the high-Tc YBa2Cu3O7-x (YBCO) superconductor as a reference and an analysis of the measurement uncertainty. To make a precision measurement and aid in the verification of the uncertainty components, we developed a cryostat system that enables temperature control in a stable manner. The expected performance of the reference superconductor yielded a zero value well below Tc, which was validated by a superconductor-superconductor thermocouple experiment. Uncertainty analysis shows that the main limiting factor for this measurement is the accuracy of the temperature difference measurement using the resistance temperature sensors, along with its analog noise. We obtained values of S = 5.6 ± 0.2 µV/K with a relative expanded uncertainty of 3% at 80 K and precisely compared the Pt value with that determined by the high-Tc Bi2Sr2Ca2Cu3O8+δ (Bi-2223) superconductor, which has a higher Tc. We found that there was no difference between the Seebeck coefficient values obtained from the YBCO and Bi-2223 references up to its Tc within the expanded measurement uncertainties of 0.3 µV/K (2σ). These results provide accurate validation that the high-Tc superconductor is a useful reference up to the liquid nitrogen temperature.
Pattern formation and chimera states in 2D SQUID metamaterials
Authors: Hizanidis J. , Lazarides N. , Tsironis G. P.
Published: January 2020

The Superconducting QUantum Interference Device (SQUID) is a highly nonlinear oscillator with rich dynamical behavior, including chaos. When driven by a time-periodic magnetic flux, the SQUID exhibits extreme multistability at frequencies around the geometric resonance, which is manifested by a “snakelike” form of the resonance curve. Repeating motifs of SQUIDs form metamaterials, i.e., artificially structured media of weakly coupled discrete elements that exhibit extraordinary properties, e.g., negative diamagnetic permeability. We report on the emergent collective dynamics in two-dimensional lattices of coupled SQUID oscillators, which involves a rich menagerie of spatiotemporal dynamics, including Turing-like patterns and chimera states. Using Fourier analysis, we characterize these patterns and identify characteristic spatial and temporal periods. In the low coupling limit, the Turing-like patterns occur near the synchronization-desynchronization transition, which can be related to the bifurcation scenarios of the single SQUID. Chimeras emerge due to the multistability near the geometric resonance, and by varying the dc component of the external force, we can make them appear and reappear and, also, control their location. A detailed analysis of the parameter space reveals the coexistence of Turing-like patterns and chimera states in our model, as well as the ability to transform between these states by varying the system parameters.
Timescale prediction of complex multi-barrier pathways using flux sampling molecular dynamics and 1D kinetic integration: Application to cellulose dehydration
Authors: Valdenaire Pierre-Louis , Pellenq Roland J. M. , Ulm Franz J. , van Duin Adri C. T. , Leyssale Jean-Marc
Published: January 2020

Reactive molecular dynamics (MD) simulations, especially those employing acceleration techniques, can provide useful insights on the mechanism underlying the transformation of buried organic matter, yet, so far, it remains extremely difficult to predict the time scales associated with these processes at moderate temperatures (i.e., when such time scales are considerably larger than those accessible to MD). We propose here an accelerated method based on flux sampling and kinetic integration along a 1D order parameter that can considerably extend the accessible time scales. We demonstrate the utility of this technique in an application to the dehydration of crystalline cellulose at temperatures ranging from 1900 K to 1500 K. The full decomposition is obtained at all temperatures apart from T = 1500 K, showing the same distribution of the main volatiles (H2O, CO, and CO2) as recently obtained using replica exchange molecular dynamics. The kinetics of the process is well fitted with an Arrhenius law with Ea = 93 kcal/mol and k0 = 9 × 1019 s−1, which are somehow larger than experimental reports. Unexpectedly, the process seems to considerably slow down at lower temperatures, severely departing from the Arrhenius regime, probably because of an inadequate choice of the order parameter. Nevertheless, we show that the proposed method allows considerable time sampling at low temperatures compared to conventional MD.
Demonstration of transport of a patterned electron beam produced by diamond pyramid cathode in an rf gun
Authors: Nichols K. E. , Andrews H. L. , Kim D. , Simakov E. I. , Conde M. , Doran D. S. , Ha G. , Liu W. , Power J. F. , Shao J. , Whiteford C. , Wisniewski E. E. , Antipov S. P. , Chen G.
Published: January 2020

We have demonstrated generation and transport of a patterned electron beam from a Diamond Field-Emitter Array (DFEA) cathode in a radio frequency (rf) gun. DFEAs are arrays of micrometer-scale pyramids with nanometer-scale tips. They can be fabricated with base widths ranging from 3 μm to 25 μm and pitches as small as 5 μm. They have an inherent 1:0.7 base to height ratio. DFEAs operate as field-emitter cathodes and potentially produce intrinsically shaped electron beams, which are of interest for a number of accelerator applications. We report on the results of a recent experiment in which a beam, consisting of several beamlets, was produced from a DFEA cathode in an rf gun and transported 2.54 m along a beam line. A macrobunch charge of 60 pC was measured at a cathode field gradient of 15.1 MV/m.
High electrical conducting deep-ultraviolet-transparent oxide semiconductor La-doped SrSnO3 exceeding ∼3000 S cm−1
Authors: Wei Mian , Sanchela Anup V. , Feng Bin , Ikuhara Yuichi , Cho Hai Jun , Ohta Hiromichi
Published: January 2020

La-doped SrSnO3 (LSSO) is known as one of the deep-ultraviolet (DUV)-transparent conducting oxides with an energy bandgap of ∼4.6 eV. Since LSSO can be grown heteroepitaxially on more wide bandgap substrates such as MgO (Eg ∼ 7.8 eV), LSSO is considered to be a good candidate for a DUV-transparent electrode. However, the electrical conductivity of LSSO films is below 1000 S cm−1, most likely due to the low solubility of the La ion in the LSSO lattice. Here, we report that high electrically conducting (>3000 S cm−1) LSSO thin films with an energy bandgap of ∼4.6 eV can be fabricated by pulsed laser deposition on a MgO substrate followed by a simple annealing in vacuum. From the X-ray diffraction and the scanning transmission electron microscopy analyses, we found that lateral grain growth occurred during the annealing, which improved the activation rate of the La ion, leading to a significant improvement of the carrier concentration (3.26 × 1020 cm−3) and Hall mobility (55.8 cm2 V−1 s−1). The present DUV-transparent oxide semiconductor would be useful as a transparent electrode for developing optoelectronic devices, which transmit and/or emit DUV-light.
Optical fiber temperature sensor based on a Mach-Zehnder interferometer with single-mode-thin-core-single-mode fiber structure
Authors: Wang Qingzhuo , Meng Hongyun , Fan Xiaofeng , Zhou Mengqi , Liu Fengxiang , Liu Chunyang , Wei Zhongchao , Wang Faqiang , Tan Chunhua
Published: January 2020

A Mach-Zehnder interferometer for measurement of temperature is proposed and experimentally demonstrated, which consists of two sections of single mode fiber (SMF) and a section of thin core fiber spliced between the two SMFs. The two welding areas are heated and stretched to improve the split and recombination of light. The wavelength of the resonant dip will shift when temperature varies due to the thermo-optic and thermal expansion effect. The experimental results show that a temperature sensitivity of 65 pm/°C with a linear correlation coefficient of 0.996 can be achieved in a temperature range from 25 °C to 80 °C. Due to its ease of manufacture, low cost, and high sensitivity, the fiber optic temperature sensor is suitable for temperature measurement applications.
The effect of a synthetic input on small-scale intermittent bursting events in near-wall turbulence
Authors: Tang Zhanqi , Jiang Nan
Published: January 2020

This study reports the effect of a synthetic input on the arrangements of near-wall small-scale intermittent bursting events. The hot-wire data were decomposed into small scales by wavelet transform, and the local energy bursts relevant to anomalous scaling were extracted and examined. The premultiplied spectral analysis revealed that the synthetic input reorganizes the intermittency distribution of the small-scale local energy bursts. The reorganization was confirmed by the cross spectra of the small-scale bursting events and the rest scales, which indicated that the synthetic input has a dominant interaction on the near-wall small-scale bursts by means of frequency coupling. The phase difference relationship demonstrated that the small-scale energy bursts are in phase with the synthetic input in the near wall region and then gradually phase-lagged to be out of phase further away from the wall. Moreover, conditional average provided a more direct configuration of the phase-switching phenomenon. The current study manifested that the synthetic input could have the ability to reorganize the near-wall small-scale intermittent bursting events in a deterministic way.
Cryogenic atomic hydrogen beam apparatus with velocity characterization
Authors: Cooper S. F. , Brandt A. D. , Rasor C. , Burkley Z. , Yost D. C.
Published: January 2020

Precision spectroscopy of hydrogen often relies on effusive thermal atomic beams, and the uncertainty in the velocity distribution of these beams can introduce systematic errors and complicate lineshape models. Here, we present an apparatus capable of high signal-to-noise studies of these velocity distributions at cryogenic temperatures for both ground state (1S) and metastable (2S) hydrogen using a simple time-of-flight technique. We also investigate how the cryogenic nozzle geometry affects these results.
Electrostatic interactions between spheroidal dielectric particles
Authors: Derbenev Ivan N. , Filippov Anatoly V. , Stace Anthony J. , Besley Elena
Published: January 2020

Theory is developed to address the significant problem of electrostatic interactions between charged polarizable dielectric spheroids. The electrostatic force is defined by particle dimensions and charge, dielectric constants of the interacting particles and medium, and the interparticle separation distance; and it is expressed in the form of an integral over the particle surface. The switching behavior between like charge repulsion and attraction is demonstrated as depending on the ratio of the major and minor axes of spheroids. When the major and minor axes are equal, the theory yields a solution equivalent to that obtained for spherical particles. Limiting cases are presented for nonpolarizable spheroids, which describe the electrostatic behavior of charged rods, discs, and point charges. The developed theory represents an important step toward comprehensive understanding of direct interactions and mechanisms of electrostatically driven self-assembly processes.
Wideband and high-efficiency planar chiral structure design for asymmetric transmission and linear polarization conversion
Authors: Long Fei , Yu Shixing , Kou Na , Zhang Can , Ding Zhao , Zhang Zhengping
Published: January 2020

The phenomenon of asymmetric transmission (AT) means the existence of a giant difference in transmittance after the incident waves pass through the special slab in two opposite directions, which is quite useful for realizing irreversible electromagnetic waves and has attracted much attention in recent years. However, it is difficult to achieve wideband asymmetric transmission and linear polarization conversion simultaneously using the bilayer transmission-mode structure. In this work, we propose and numerically investigate a high-efficiency transmission-mode metamaterial that consists of twisted multigap rings on both sides of a dielectric slab. Benefiting from the antisymmetric design of the split ring bilayer transmitarray element, the proposed structure excites the electric and magnetic dipole resonances with mutual interference, thereby simultaneously achieving asymmetric transmission and linear polarization conversion. The proposed structure is designed, fabricated, and measured, which can realize a good agreement between the measurement results and the anticipation. Within the frequency range from 12.7 to 17 GHz, the AT parameter can be close to 0.9 and the polarization conversion ratio can be more than 93%.
Extremely flat surface full granular media with cap layer consisting of high-Ku CoPt grains and ferromagnetic oxide grain boundaries
Authors: Tham Kim Kong , Kushibiki Ryosuke , Kamada Tomonari , Saito Shin
Published: January 2020

Investigation of magnetic properties and nanostructure of stacked media with a CoPt-B2O3 granular recording layer (GRL) and granular cap layers (CL) with CoPt and a typical ferromagnetic oxide of rare earth (RE) oxide (RE oxide: Gd2O3, Nd2O3, Sm2O3, and CeO2) are reported. CoPt-RE oxide granular layer shows higher saturation magnetization and magnetic anisotropy than that of CoPtCrB continuous layer. In stacked media with CoPt-Gd2O3 granular CL (9 nm), nucleation field increases from 0.7 to 0.8 kOe and saturation field decreases from 21.5 to 12.5 kOe with comparable values to those of CoPtCrB continuous CL. This indicates that CoPt-RE oxide granular CL is effective to control intergranular exchange coupling. Reduction of coercivity distribution ratio (∆Hc/Hc) from 0.15 to 0.09 which is comparable to that of CoPtCrB continuous CL when CoPt-Gd2O3 granular CL thickness is changed from 4 to 9 nm is observed. This means CoPt-Gd2O3 granular CL is effective to reduce switching field distribution. Furthermore, significant reduction of surface roughness (Ra) for media with CoPt-Gd2O3 granular CL (9 nm) from 0.32 to 0.25 nm is observed. This reveals that CoPt-RE oxide granular CL has a great impact to induce stacked media with flat surface. Based on the cross-section observation by TEM, the media with CoPt-Gd2O3 granular CL shows continuous structure of grain boundaries from the GRL up to the CL and which results in one-on-one growth of magnetic grain with homogeneous columnar structure. Focusing on the surface morphology, media with CoPt-Gd2O3 granular CL shows smoother surface than that of media with CoPtCrB continuous CL which supports the Ra evaluation result. These results indicate that the employment of granular CoPt-RE oxide for CL is not only to reduce switching field distribution but also to flatten surface of the stacked media.
Optimum selective emitters for efficient thermophotovoltaic conversion
Authors: Hassan Sakib , Doiron Chloe F. , Naik Gururaj V.
Published: January 2020

Though thermophotovoltaic (TPV) systems have been studied for many decades, the demonstrated conversion efficiencies have remained far lower than the theoretical maximum. Here, in this work, we investigate the reason for low efficiency, especially in TPV systems employing selective thermal emitters, and determine design pathways toward high efficiency. We model both the optical and optoelectronic components of the TPV system and study the influence of the emitter selectivity on the optimum bandgap of the photovoltaic cell, heat sink requirements, and maximum conversion efficiency for any given emitter temperature from 1000 to 2000 K. Our calculations suggest that thermal emitters with at least 20 dB suppression of sub-bandgap emission and an emission enhancement of 100× can push the overall efficiency to 70% of Carnot's limit. Furthermore, we show that such an extreme requirement on suppression is at the performance limits for resonant thermal emitters employing refractory plasmonic materials such as Mo, W, Ta, TiN, and carbon nanotubes.
Evaluation of the AMOEBA force field for simulating metal halide perovskites in the solid state and in solution
Authors: Rathnayake P. V. G. M. , Bernardi Stefano , Widmer-Cooper Asaph
Published: January 2020

In this work, we compare the existing nonpolarizable force fields developed to study the solid or solution phases of hybrid organic-inorganic halide perovskites with the AMOEBA polarizable force field. The aim is to test whether more computationally expensive polarizable force fields like AMOEBA offer better transferability between solution and solid phases, with the ultimate goal being the study of crystal nucleation, growth, and other interfacial phenomena involving these ionic compounds. In the context of hybrid perovskites, AMOEBA force field parameters already exist for several elements in solution, and we decided to leave them unchanged and to only parameterize the missing ones (Pb2+ and CH3NH3+ ions) in order to maximize transferability and avoid overfitting to the specific examples studied here. Overall, we find that AMOEBA yields accurate hydration free energies (within 5%) for typical ionic species while showing the correct ordering of stability for the different crystal polymorphs of CsPbI3 and CH3NH3PbI3. Although the existing parameters do not accurately reproduce all transition temperatures and lattice parameters, AMOEBA offers better transferability between solution and solid states than existing nonpolarizable force fields.
Enhanced emission from ultra-thin long wavelength infrared superlattices on epitaxial plasmonic materials
Authors: Nordin L. , Li K. , Briggs A. , Simmons E. , Bank S. R. , Podolskiy V. A. , Wasserman D.
Published: January 2020

Molecular beam epitaxy allows for the monolithic integration of wavelength-flexible epitaxial infrared plasmonic materials with quantum-engineered infrared optoelectronic active regions. We experimentally demonstrate a sixfold enhancement in photoluminescence from ultrathin (total thickness λo/33) long wavelength infrared (LWIR) superlattices grown on highly doped semiconductor “designer metal” virtual substrates when compared to the same superlattice grown on an undoped virtual substrate. Analytical and numerical models of the emission process via a dyadic Green's function formalism are in agreement with experimental results and relate the observed enhancement of emission to a combination of Purcell enhancement due to surface plasmon modes as well as directionality enhancement due to cavity-substrate-emitter interaction. The results presented provide a potential pathway toward efficient, ultrasubwavelength LWIR emitter devices, as well as a monolithic epitaxial architecture offering the opportunity to investigate the ultimate limits of light-matter interaction in coupled plasmonic/optoelectronic materials.
Photon-assisted heat engines in the THz regime
Authors: Sengupta Parijat , Das Saptarshi
Published: January 2020

The generation of thermal currents in a miniaturized device modeled as a channel connected to reservoirs maintained at different temperatures and coupled to a periodic THz driving source is reported in this letter. Primarily, we show that while thermally activated electrons can be pumped from the hot reservoir into the cold side, the quantum of charge flow increases in the presence of the periodic source. We explain this phenomenon by taking recourse to the Floquet theory guided rearrangement of the energy levels under periodic driving, which, in turn, augments the electron injection into the channel. The calculations uncover a useful feature whereby the strength of such a thermally-pumped current is amenable through a joint control of the amplitude and frequency of the signal, offering an additional experimentally-adjustable set of tools to regulate their flow. In the final part, the Seebeck coefficient and the thermoelectric figure-of-merit for this setup are analytically determined. Results are shown for classes of materials defined by linear and quadratic dispersion.
Dynamics of an elliptical ferromagnetic skyrmion driven by the spin–orbit torque
Authors: Xia Jing , Zhang Xichao , Ezawa Motohiko , Shao Qiming , Liu Xiaoxi , Zhou Yan
Published: January 2020

Magnetic skyrmions are promising building blocks for developing information storage and computing devices. It can be stabilized in a ferromagnetic thin film with the Dzyaloshinskii-Moriya interaction (DMI). The moving ferromagnetic skyrmion may show the skyrmion Hall effect, that is, the skyrmion shows a transverse shift when it is driven by a spin current. Here, we numerically and theoretically study the current-driven dynamics of a ferromagnetic nanoscale skyrmion in the presence of the anisotropic DMI, where the skyrmion has an elliptical shape. The skyrmion Hall effect of the elliptical skyrmion is investigated. It is found that the skyrmion Hall angle can be controlled by tuning the profile of the elliptical skyrmion. Our results reveal the relation between the skyrmion shape and the skyrmion Hall effect, which could be useful for building skyrmion-based spintronic devices with a preferred skyrmion Hall angle. Also, our results provide a method for the minimization of the skyrmion Hall angle for applications based on in-line motion of skyrmions.
Giant elastocaloric effect in a Mn-rich Ni44Mn46Sn10 directionally solidified alloy
Authors: Zhang Guoyao , Li Zongbin , Yang Jiajing , Yang Bo , Wang Dunhui , Zhang Yudong , Esling Claude , Hou Long , Li Xi , Zhao Xiang , Zuo Liang
Published: January 2020

The superelastic and elastocaloric properties of a Mn-rich Ni44Mn46Sn10 polycrystalline alloy prepared by directional solidification were studied. Owing to the coarse columnar shaped grains with strong ⟨001⟩A preferred orientation, a large superelastic strain up to 8% and a transformation strain of 5.6% can be obtained through compressive stress induced martensitic transformation. Moreover, a giant adiabatic temperature variation up to –18 K was achieved on removing the stress. Such a remarkable elastocaloric effect is attributed to the large transformation entropy change through composition modification and the enhanced mechanical properties due to the formation of a highly textured microstructure in the directionally solidified alloy.