bluuebunny/crossref_metadata_2025 huggingface dataset:
Computational fluid dynamics calculus and analysis for gas and water turbines
Authors: Vilag Valeriu , Zheleva Ivanka , Popescu Jenia , Tujarov Krasimir
Published: January 2018

The paper presents the utilization of Computational Fluid Dynamics for calculating the flow through turbines. The first and most extended part of the paper is focused on gas turbines where the simulations are very precise and can be successfully used even for optimization of blade geometry. Flow details and results for an axial turbine are presented along with a proposal of optimization algorithm. The second part of the paper is dedicated to water turbines and there is presented the calculus realized for a kinetic water turbine. I this case, the flow around the turbine blades is presented and some data about the predicted performances along with many ways for improving the simulations. The conclusions of the paper are related to similarities and differences between the two types of simulations and to the many ways of using these simulations for practical applications.
Design of short low speed Göttingen type wind tunnel: CFD simulation
Authors: Weisweiler Hardy , Kojouharova Jasmina , Dückershoff Roland
Published: January 2018

The paper is focused on design simulations by the means of commercial software for a low speed circuit wind tunnel with an open test section, recently built at the Department of Mechanical Engineering, Mechatronics and Materials Technology at THM University of Applied Sciences in Friedberg. The proposed wind tunnel has a test section with cross sectional area of 1 X 1 m2 and a length of 1.6 m. The maximum achievable speed is about 50 m/s with empty test section. The simulation had the target to propose and to verify various geometries - test chamber, tunnel contraction, diffuser etc. as well the tunnel corner including the vanes. In addition, the influence of the vanes number and their shape on the ventilator power needed and the flow velocity uniformity as well, have been subjects of the investigation. Also the ventilator type (rotational segment) impact on the flow pattern within the operational area has been scrutinized.
A multiphase flow in the antroduodenum: some results of the mathematical modelling and computational simulation
Authors: Kamaltdinov Marat , Trusov Peter , Zaitseva Nina
Published: January 2018

This work is devoted to a problem of creation of a multiphase flow model in an antroduodenum that includes the lower part of the stomach and the upper part of the small intestine (duodenum). The mathematical model is developed for the next purposes: description of the process of digestion in normal physiological state and with functional disorders, prediction of the flow characteristics in distinct conditions. The antroduodenum is considered as a complex form canal with moving boundaries. The mathematical statement of the problem includes mass and momentum conservation equations for phases and components as well as initial and boundary conditions with peristaltic movement. To describe secretion and absorption processes we use mass sources/sinks in a layer adjacent to the tract wall. Using computational simulation we got the digestion processes characteristics in dynamic: pH of the medium, components and phases velocities and fractions. In some scenarios with secretory and motor disorders we identified zones of abnormal acidity. The results of the simulation showed that motor functionality of the antrum and pyloric sphincter affect the stomach evacuation. Additionally, the chemical absorption rate is analyzed in scenarios with distinct food parameters (size, viscosity, density).
Non-destructive monitoring of tensile of mild steel samples by magnetic Barkhausen and ultrasonic methods
Authors: Ivanova Yonka
Published: January 2018

The paper presents an experimental study of deformations of mild steel samples by magnetic Barkhausen, magnetoacoustic and ultrasonic methods. The purpose of the study is to investigate and analyze the dependence between mechanical, magnetic and acoustic properties and to find appropriate parameters for stress state evaluation in the elastic and plastic regions.
Preparation of sol-gel SiO2 coatings on steel and their corrosion resistance
Authors: Stambolova Irina , Yordanov Stancho , Lakov Lyuben , Vassilev Sasho , Blaskov Vladimir , Jivov Bojidar
Published: January 2018

A protective SiO2 coating was prepared by sol-gel method on stainless steel plates, using precursor solutions having 2 different concentrations: low (0.5M) and high (2M) concentration. The dip coating-drying cycles have been repeated three times, after that the coatings were thermally treated at 300°C or 500°C in air. Scanning electron microscopy (SEM), AFM and X-ray diffraction analyses have been applied. The corrosion resistances of SiO2 coated steels were examined in NaCl medium for 346 hours. Many microcracks and craters in the samples, prepared from solution of high concentration appear after corrosion attack. The coatings obtained from solution of low concentrations reveals almost unchanged surface structure without visible cracks and pits. The evaluated corrosion rate of this coating is lower than those of uncoated steel.
Theoretical analysis and experiments for the carburization of vanadium-bearing hot metal
Authors: Ma Deng , Wu Wei , Dai Shifan , Liu Zhibin
Published: January 2018

In this study, the feasibility of the carburization of vanadium-bearing hot metal was first investigated by thermodynamic analysis. Next, three carburizers, namely a low-nitrogen carburizer, anthracite, and coke, were used for carburization of 500 g of vanadium-bearing hot metal at 1450 °C, 1500 °C, and 1550 °C, respectively. The carbon increments for the low-nitrogen carburizer, anthracite and coke followed decreasing order in the temperature range from 1450 °C to 1550 °C. Anthracite was the most cost-effective carburizer. Hence, anthracite is used in pilot-scale experiments of the vanadium-bearing hot metal (100 kg and 200 kg). Finally, vanadium extraction experiments of the vanadium-bearing hot metal were carried out in a top-bottom-combined blowing induction furnace. It is proved that the average superheat degree of semi-steel increases from 100 °C to 198 °C by the carburization of vanadium-containing hot metal.
La reproductibilité de la position d'équilibre naturel sur photographie
Authors: Eddo Marie-Line , El Hayeck Émilie , Hoyeck Maha , Khoury Élie , Ghoubril Joseph
Published: January 2018

Introduction : Cette étude a pour objectif d'évaluer la reproductibilité de la position d'équilibre naturel en fonction du temps sur des photographies de profil. Matériels et Méthodes : L'échantillon est de 96 étudiants de la faculté de médecine dentaire de l'université Saint-Joseph de Beyrouth, âgés de 20 à 30 ans. Deux photographies de profil ont été prises pour chaque sujet dans sa position d'équilibre naturel, à intervalle d'une semaine. L'angle formé par la tangente à la columelle du nez passant par le point sous-nasal et la vraie verticale a été mesuré. Résultats : Il n'y a pas eu de différence significative entre T0 et T1 (E = 1,065°). Discussion : D'autres études confirment cette reproductibilité avec le temps. La position d'équilibre naturel peut donc être adoptée comme orientation au niveau des photographies de profil en orthodontie.
Cranial Nerve Preservation Following Surgical Treatment for Epidermoid Cysts of the Posterior and Middle Fossae
Authors: Grahnke Kurt , Burkett Daniel , Li Daphne , Szujewski Caroline , Leonetti John , Anderson Douglas
Published: January 2018

Epidermoid cysts are rare lesions, accounting for 0.2 to 1.8% of all intracranial tumors. They most commonly occur in the cerebellopontine angle where they may cause a breadth of neurologic complications due to mass effect on the nearby cranial nerves (CN), vascular structures, and the brain stem. Treatment of epidermoid cysts is surgical, with the goal of complete resection using microsurgical technique and even more importantly preservation of the involved CNs, vasculature, and brain parenchyma. Successful surgery can result in total resolution of symptoms, but, in certain situations, may not be advisable due to adherence, scarring, or inflammation making dissection of CN fascicles difficult and possibly hazardous. We conducted a retrospective review from 1998 to 2016 and compiled a series of 28 skull base epidermoid cysts operated on at our institution. Cases were evaluated for presenting symptoms, history of prior resection, and postoperative results including CN function, extent of resection, residual tumor, and need for reoperations. The average tumor size (largest diameter) was 3.9 cm with a range of 1 to 7cm. Eighteen of twenty-eight (64%) patients underwent a gross total resection and ten underwent subtotal resection. No patients, whether presenting with CN deficits or not, experienced permanent worsening of CN function following surgery. Complete resection of epidermoid cysts should remain a high priority of therapy, but, in our opinion, preservation of CN function should be a primary goal, determining the extent of resection to provide patients with the highest quality of life possible following surgery.
Endoscopic Endonasal Resection of Retrochiasmatic Craniopharyngioma with Fascia Lata Button and Nasoseptal Flap Reconstruction
Authors: Kshettry Varun , Nyquist Gurston , Evans James
Published: January 2018

Surgery for craniopharyngiomas can be challenging due to the involvement of multiple critical neurovascular structures. The expanded endoscopic endonasal approach can provide superior access to suprasellar craniopharyngiomas, particularly with retrochiasmatic extension and significant hypothalamic involvement. We describe the surgical technique used to treat a 30-year-old patient who presented with 4 weeks of worsening vision, fatigue, and memory loss. His vision was counting fingers at 1 feet on the right and 20/800 on the left with a temporal hemianopsia. Laboratory evaluation demonstrated central hypoadrenalism, hypothyroidism, and hypogonadism. Imaging showed a large solid and cystic suprasellar mass. The transtubercular approach with removal of the lateral tubercular strut can provide wide bilateral access to the opticocarotid region. The superior intercavernous sinus must be coagulated and ligated. Initial arachnoid dissection is centered at the midline, mobilizing the superior hypophyseal branches to the optic apparatus laterally. The cyst capsule is opened and care is taken to minimize spillage of cyst fluid into the subarachnoid space. Central debulking and then extracapsular dissection is performed under direct visualization using sharp dissection. Reconstruction of the dura is performed with an inlay/onlay fascia lata button that is held together with four sutures that hold the graft edges against the native dural edges. This is followed by vascularized nasoseptal flap reconstruction. No lumbar drain or nonabsorbable packing is required. The patient's vision had dramatic improvement and by 1 week postoperatively was 20/20 with full visual fields. Postoperative diabetes insipidus was managed with nasal desmopressin. Postoperative MRI demonstrated complete removal.

The link to the video can be found at: https://youtu.be/QQxCNUcq1qg.
Acute hepatitis as a prequel to very severe aplastic anemia
Authors: Weiler-Normann Christina , Hartl Johannes , Weidemann Sören , von Pein Ute-Marie , Fiedler Walter , Schramm Christoph , Brinkert Florian , Kröger Nicolaus , Christopeit Maximilian
Published: January 2018

Severe aplastic anemia is a rare and potentially life-threatening disease of the bone marrow often requiring allogeneic hematopoietic stem cell transplantation. Pathogenesis of the disease can vary and often remains enigmatic. Occasionally, severe aplastic anemia is associated with prior severe acute hepatitis. Differential diagnosis of acute non-viral hepatitis challenges the physician as pathogenesis remains unclear.

We here present a case of a young patient presenting with acute hepatitis followed by severe aplastic anemia successfully treated with allogeneic hematopoietic stem cell transplantation. Due to immunosuppressive treatment with azathioprine for acute hepatitis of putative autoimmune pathogenesis and coincident infection with parvovirus B19, diagnosis of the sequential disease of acute hepatitis followed by severe aplastic anemia was complicated. We discuss the caveats and present a review of the literature.
Die Fremdkörperingestion – eine seltene Ursache persistierender, unklarer abdomineller Schmerzen
Authors: Kasper Philipp , Kütting Fabian , Schlößer Hans , Mönig Stefan , Goeser Tobias , Jaspers Natalie
Published: January 2018

Anamnese und klinischer Befund Ein 50-jähriger Patient stellt sich mit rechtsseitigen Unterbauchschmerzen in der Notaufnahme vor. Er gibt an, dass jene Beschwerden seit ca. 5 Monaten bestünden und bei der Miktion an Intensität zunähmen.

Untersuchungen Nach einer Vielzahl frustraner diagnostischer Maßnahmen (CT Abdomen, MR-Sellink, Ileokoloskopie) gelingt es letztlich mittels Darmsonografie, einen ingestierten Zahnstocher im terminalen Ileum als Ursache für die Beschwerden zu identifizieren. Jener perforiert die Darmwand lokal und affektiert die angrenzende Blasenwand bei jeder Erhöhung des intraabdominellen Druckes schmerzhaft.

Therapie und Verlauf Explorative Laparotomie mit Nachweis eines entzündlichen Konglomerattumors mit ileosigmoidaler Fistel im rechten Unterbauch. Die Entzündungsreaktion wird durch einen das terminale Ileum zweifach perforierenden Zahnstocher verursacht. Die operative Versorgung erfolgt mittels Ileumsegmentresektion und Sigmaresektion mit End-zu-End-Anastomosierung. Im postoperativen Verlauf kommt es zu einer subkutanen Wundheilungsstörung, die mittels VAC-Therapie versorgt wird. Am 16. postoperativen Tag kann der Patient in einem guten Allgemeinzustand nach Hause entlassen werden.

Folgerung Eine Fremdkörperingestion stellt eine seltene, aber relevante Differenzialdiagnose unklarer abdomineller Schmerzen, insbesondere im Kindesalter, dar. Neben einer ausführlichen Anamnese sollte als primäre apparative Maßnahme stets zunächst eine qualifizierte und sorgfältig durchgeführte Abdomensonografie erfolgen, mithilfe derer auch strahlentransparente ingestierte Fremdkörper detektiert werden können.
Regionale Versorgungsaspekte des akuten Myokardinfarktes im Nordosten Deutschlands
Authors: Salzwedel Annett , Völler Heinz , Reibis Robert , Bonaventura Klaus , Behrens Steffen , Reibis Rona
Published: January 2018

Hintergrund In den letzten Jahrzehnten führte die leitliniengerechte Therapie des akuten Myokardinfarktes (MI) zu einer Mortalitätsreduktion in Deutschland, wobei zwischen einzelnen Bundesländern erhebliche Unterschiede beschrieben werden. Ziel war es daher, die aktuelle Versorgungssituation von Patienten mit MI in der Region Nordost-Deutschland (Berlin, Brandenburg [BRB] und Mecklenburg-Vorpommern [MV]) zu untersuchen und Prädiktoren der 1-Jahresmortalität unter Berücksichtigung der regionalen Zuordnung zu identifizieren.

Methode Auf Basis pseudonymisierter Abrechnungsdaten einer gesetzlichen Krankenversicherung wurden für das Jahr 2012 anhand des ICD 10-Codes I21 und I22 von 1 387 084 Versicherten insgesamt 6733 Patienten mit stationärer Aufnahme bei MI gefiltert. Neben der Krankenhaus- und 1-Jahresmortalität wurden potenzielle Prognoseprädiktoren unter Berücksichtigung von Komorbiditäten, periinfarziellen Prozeduren und sekundärpräventiver Pharmakotherapie erfasst und im Ländervergleich analysiert.

Ergebnisse Sowohl die Krankenhaus- als auch die 1-Jahresmortalitätsrate der einzelnen Länder (Berlin 13,6 resp. 27,5 %, BRB 13,9 resp. 27,9 %, MV 14,4 resp. 29,0 %) war vergleichbar zur Gesamtrate (13,9 % resp. 28,0 %) und im Ländervergleich weitgehend identisch. Die multiple Analyse der Einflussfaktoren auf die 1-Jahresmortalität identifizierte vor allem die Koronarangiografie (OR 0,42, 95 % KI 0,35 – 0,51, p < 0,001) und die Umsetzung der pharmakologischen Leitlinienempfehlungen (OR 0,14, 95 % KI 0,12 – 0,17, p < 0,001) als wesentliche Maßnahmen zur Risikoreduktion. Bei beiden Einflussfaktoren lagen univariat keine statistischen Unterschiede zwischen den drei Bundesländern vor.

Schlussfolgerung Die vorliegenden Daten lassen auf eine vergleichbare stationäre und poststationäre Versorgung und 1-Jahresprognose von Patienten mit akutem MI in den Bundesländern Berlin, Brandenburg und Mecklenburg-Vorpommern in der untersuchten Population schließen, wobei insbesondere der Durchführung einer Koronarangiografie und der adäquaten Umsetzung einer leitliniengerechten Pharmakotherapie prognostische Bedeutung zukommt.
Kombination von NAFLD Fibrosis Score und transienter Elastografie zur Identifikation mittelgradiger Fibrosestadien (II/III) bei nicht-alkoholischer Fettlebererkrankung
Authors: Drolz Andreas , Wehmeyer Malte , Diedrich Tom , Piecha Felix , Schulze zur Wiesch Julian , Kluwe Johannes
Published: January 2018

Einleitung Die nicht-alkoholische Fettlebererkrankung (NAFLD) gehört mittlerweile weltweit zu den häufigsten Ursachen für eine chronische Leberschädigung. Aktuell sind die therapeutischen Optionen limitiert und neue pharmakologische Therapieoptionen werden primär im Rahmen von Studien untersucht. Da viele aktuelle Studien zumeist auf NAFLD-Patienten mit den Fibrosestadien II und III (nach Kleiner) abzielen, ist die nicht-invasive Identifikation dieser Patienten von zunehmender Bedeutung.

Ziel Evaluation von Lebersteifigkeitsmessung (LSM) und NAFLD Fibrosis Score (NFS) im Hinblick auf die Vorhersage eines Fibrosestadiums II/III.

Methoden Patienten mit bioptisch gesicherter NAFLD Diagnose wurden in die Studie eingeschlossen. Vor der Leberbiopsie wurden alle Patienten klinisch, laborchemisch und mittels LSM evaluiert. Anschließend wurde die Vorhersagekraft von NFS und LSM im Hinblick auf das Vorliegen einer Fibrose Stadium II/III untersucht.

Ergebnisse 134 NALFD-Patienten wurden in die Studie eingeschlossen und untersucht. Das mittlere Alter betrug 53 (IQR 36 – 60) Jahre, 55 Patienten (41 %) waren weiblich. 82 % der Patienten waren übergewichtig/adipös mit typischen Befundkonstellationen des Metabolischen Syndroms. 84 Patienten (66 %) zeigten Zeichen einer Fibrose, bei 42 (50 %) bestand eine fortgeschrittene Fibrose. LSM und NFS korrelierten mit dem Fibrosestadium (r = 0,696 bzw. r = 0,685, p < 0,01). NFS-Werte zwischen –2,0 und + 0,5 und LSM-Werte zwischen 8 und 22kPa waren mit hoher Wahrscheinlichkeit für das Vorliegen eines Fibrosestadiums II/III assoziiert. Wenn beide dieser Kriterien erfüllt waren, bestand zu 61 % ein Fibrosestadium II/II. Wenn hingegen keines der beiden Kriterien erfüllt war, lag die Wahrscheinlichkeit für eine Fibrose II/III lediglich bei 6 % (negativer prädiktiver Wert 94 %).

Schlussfolgerung Die Kombination von LSM und NFS ermöglicht die Identifikation von Patienten mit erhöhtem Risiko für ein Fibrosestadium II/III. Daher könnte der Einsatz dieser beiden nicht-invasiven Tests speziell in Kombination als Screening-Tool für NAFLD-Patienten im Hinblick auf das Vorhandensein einer Fibrose II/III eingesetzt werden. Durch den Einsatz dieser Verfahren könnten außerdem nicht-notwendige Biopsien vermieden werden.
Maximising the availability and use of high-quality evidence for policymaking: collaborative, targeted and efficient evidence reviews
Authors: Gavine Anna , MacGillivray Steve , Ross-Davie Mary , Campbell Kirstie , White Linda , Renfrew Mary
Published: January 2018

A number of barriers have been identified to getting evidence into policy. In particular, a lack of policy relevance and lack of timeliness have been identified as causing tension between researchers and policy makers. Rapid reviews are used increasingly as an approach to address timeliness, however, there is a lack of consensus on the most effective review methods and they do not necessarily address the need of policy makers. In the course of our work with the Scottish Government’s Review of maternity and neonatal services we developed a new approach to evidence synthesis, which this paper will describe. We developed a standardised approach to produce collaborative, targeted and efficient evidence reviews for policy making. This approach aimed to ensure the reviews were policy relevant, high quality and up-to-date, and which were presented in a consistent, transparent, and easy to access format. The approach involved the following stages: 1) establishing a review team with expertise both in the topic and in systematic reviewing, 2) clarifying the review questions with policy makers and subject experts (i.e., health professionals, service user representatives, researchers) who acted as review sponsors, 3) developing review protocols to systematically identify quantitative and qualitative review-level evidence on effectiveness, sustainability and acceptability; if review level evidence was not available, primary studies were sought, 4) agreeing a framework to structure the analysis of the reviews around a consistent set of key concepts and outcomes; in this case a published framework for maternal and newborn care was used, 5) developing an iterative process between policy makers, reviewers and review sponsors, 6) rapid searches and retrieval of literature, 7) analysis of identified literature which was mapped to the framework and included review sponsor input, 8) production of recommendations mapped to the agreed framework and presented as ‘summary topsheets’ in a consistent and easy to read format. Our approach has drawn on different components of pre-existing rapid review methodology to provide a rigorous and pragmatic approach to rapid evidence synthesis. Additionally, the use of a framework to map the evidence helped structure the review questions, expedited the analysis and provided a consistent template for recommendations, which took into account the policy context. We therefore propose that our approach (described in this paper) can be described as producing collaborative, targeted and efficient evidence reviews for policy makers.
Research Update: Programmable tandem repeat proteins inspired by squid ring teeth
Authors: Pena-Francesch Abdon , Domeradzka Natalia E. , Jung Huihun , Barbu Benjamin , Vural Mert , Kikuchi Yusuke , Allen Benjamin D. , Demirel Melik C.
Published: January 2018

Cephalopods have evolved many interesting features that can serve as inspiration. Repetitive squid ring teeth (SRT) proteins from cephalopods exhibit properties such as strength, self-healing, and biocompatibility. These proteins have been engineered to design novel adhesives, self-healing textiles, and the assembly of 2d-layered materials. Compared to conventional polymers, repetitive proteins are easy to modify and can assemble in various morphologies and molecular architectures. This research update discusses the molecular biology and materials science of polypeptides inspired by SRT proteins, their properties, and perspectives for future applications.
Lateral movements in Rayleigh–Taylor instabilities due to frontiers. Numerical analysis
Authors: Fernandez D. , Binda L. , Zalts A. , El Hasi C. , D'Onofrio A.
Published: January 2018

Numerical simulations were performed for Rayleigh-Taylor (RT) hydrodynamic instabilities when a frontier is present. The frontier formed by the interface between two fluids prevents the free movement of the fingers created by the instability. As a consequence, transversal movements at the rear of the fingers are observed in this area. These movements produce collapse of the fingers (two or more fingers join in one finger) or oscillations in the case that there is no collapse. The transversal velocity of the fingers, the amplitude of the oscillations, and the wave number of the RT instabilities as a function of the Rayleigh number (Ra) were studied near the frontier. We verified numerically that in classical RT instabilities, without a frontier, these lateral movements do not occur; only with a physical frontier, the transversal displacements of the fingers appear. The transverse displacement velocity and the initial wave number increase with Ra. This leads to the collapse of the fingers, diminishing the wave number of the instabilities at the interface. Instead, no significant changes in the amplitude of the oscillations are observed modifying Ra. The numerical results are independent of the type or origin of the frontier (gas-liquid, liquid-liquid, or solid-liquid). The numerical results are in good agreement with the experimental results reported by Binda et al. [Chaos 28, 013107 (2018)]. Based on these results, it was possible to determine the cause of the transverse displacements, which had not been explained until now.
Spontaneous Rayleigh-Brillouin scattering spectral analysis based on the Wiener filter
Authors: Wu Tao , Shang Jingcheng , Yang Chuanyin , Zhang Xinyi , Yu Huan , Mao Qibo , He Xingdao , Chen Zhongping
Published: January 2018

In this paper, a spontaneous Rayleigh-Brillouin scattering spectrometer is developed to measure the gaseous spontaneous Rayleigh-Brillouin scattering profiles over the pressure range from 1 to 5 atm for a wavelength of 532nm at a constant room temperature of 296K and a 90o scattering angle. In order to make a direct comparison between the experimentally obtained spectrum and the theoretical spectrum calculated from the Tenti S6 model, the measured spontaneous Rayleigh-Brillouin scattering signal is deconvolved by the Wiener filtering. The purpose is to remove the effect on the spectrum by the transmission function of the Fabry-Perrot scanning interferometer. The results of the comparison show that the deconvolved spectra are consistent with the theoretical spectra calculated from the Tenti S6 model, and thus confirm that the deconvolution based on the Wiener filter is able to process the measured spectra and improve the spectral resolution. Some factors that influence the accuracy of deconvolution are analyzed and discussed. At the same time, another comparison between the raw experimentally obtained spectra and the theoretical spectra calculated by convolving the Tenti S6 model with instrument function of the measurement system is performed in the same experimental condition. The results of the two comparisons show that, compared with the raw experimentally obtained spectrum, the deconvolved spectrum matches the theoretically calculated spectrum more accurately under lower pressure (≤2atm) than under relative higher pressure (>2atm).
Two-well quantum cascade laser optimization by non-equilibrium Green's function modelling
Authors: Franckié M. , Bosco L. , Beck M. , Bonzon C. , Mavrona E. , Scalari G. , Wacker A. , Faist J.
Published: January 2018

We present a two-quantum well THz intersubband laser operating up to 192 K. The structure has been optimized using non-equilibrium Green's function model. The result of this optimization was confirmed experimentally by growing, processing, and measuring a number of proposed designs. At high temperature (T > 200 K), the simulations indicate that lasing fails due to a combination of electron-electron scattering, thermal backfilling, and, most importantly, re-absorption coming from broadened states.
Backscatter spectra measurements of the two beams on the same cone on Shenguang-III laser facility
Authors: Zha Weiyi , Yang Dong , Xu Tao , Liu Yonggang , Wang Feng , Peng Xiaoshi , Li Yulong , Wei Huiyue , Liu Xiangming , Mei Yu , Yan Yadong , He Junhua , Li Zhichao , Li Sanwei , Jiang Xiaohua , Guo Liang , Xie Xufei , Pan Kaiqiang , Liu Shenye , Jiang Shaoen , Zhang Baohan , Ding Yongkun
Published: January 2018

In laser driven hohlraums, laser beams on the same incident cone may have different beam and plasma conditions, causing beam-to-beam backscatter difference and subsequent azimuthal variations in the x-ray drive on the capsule. To elucidate the large variation of backscatter proportion from beam to beam in some gas-filled hohlraum shots on Shenguang-III, two 28.5° beams have been measured with the Stimulated Raman Scattering (SRS) time-resolved spectra. A bifurcated fiber is used to sample two beams and then coupled to a spectrometer and streak camera combination to reduce the cost. The SRS spectra, characterized by a broad wavelength, were further corrected considering the temporal distortion and intensity modulation caused by components along the light path. This measurement will improve the understanding of the beam propagation inside the hohlraum and related laser plasma instabilities.
Nanoscale spatial analysis of clay minerals containing cesium by synchrotron radiation photoemission electron microscopy
Authors: Yoshigoe Akitaka , Shiwaku Hideaki , Kobayashi Toru , Shimoyama Iwao , Matsumura Daiju , Tsuji Takuya , Nishihata Yasuo , Kogure Toshihiro , Ohkochi Takuo , Yasui Akira , Yaita Tsuyoshi
Published: January 2018

A synchrotron radiation photoemission electron microscope (SR-PEEM) was applied to demonstrate the pinpoint analysis of micrometer-sized weathered biotite clay particles with artificially adsorbed cesium (Cs) atoms. Despite the insulating properties of the clay, we observed the spatial distributions of constituent elements (Si, Al, Cs, Mg, and Fe) without charging issues and clarified reciprocal site-correlations among these elements with nanometer resolution. We found that Cs atoms were likely to be adsorbed evenly over the entire particle; however, we identified an occupational conflict between Cs and Mg atoms, implying that Cs sorption involves ion exchange processes. Spatially resolved X-ray absorption spectra (XAS) of the Cs4,5 M-edge region showed Cs to be present in a monocation state (Cs+) as typically observed for Cs compounds. Further pinpoint XAS measurements were also performed at the Fe L2,3-edge to determine the chemical valence of the Fe atoms. The shapes of the spectra were similar to those for Fe2O3, indicating that Fe in the clay was in a 3+ oxidation state. From these observations, we infer that charge compensation facilitates Cs adsorption in the vicinity of a substitution site where Si4+ ions are replaced by Fe3+ ions in SiO4 tetrahedral sheets. Our results demonstrate the utility of SR-PEEM as a tool for spatially resolved chemical analyses of various environmental substances, which is not limited by the poor conductivity of samples.
Influence of MgO barrier quality on spin-transfer torque in magnetic tunnel junctions
Authors: Tiwari Dhananjay , Sharma Raghav , Heinonen O. G. , Åkerman Johan , Muduli P. K.
Published: January 2018

We studied the bias dependence of spin transfer torque in the MgO-based magnetic tunnel junction using a field-modulated spin torque ferromagnetic resonance measurement technique for three devices with tunneling magnetoresistances (MRs) of 60%, 67%, and 73%, respectively. The devices with a lower MR ratio showed the presence of multiple modes, while the device with higher MR (73%) showed a single resonance mode. We found a lower out-of-plane torkance in our devices compared to the in-plane torkance. The out-of-plane torque is linear with applied bias, while the bias dependence of in-plane torque shows a strong dependence on the MR ratio and hence the barrier quality.
Nanoscale structural and chemical analysis of F-implanted enhancement-mode InAlN/GaN heterostructure field effect transistors
Authors: Tang Fengzai , Lee Kean B. , Guiney Ivor , Frentrup Martin , Barnard Jonathan S. , Divitini Giorgio , Zaidi Zaffar H. , Martin Tomas L. , Bagot Paul A. , Moody Michael P. , Humphreys Colin J. , Houston Peter A. , Oliver Rachel A. , Wallis David J.
Published: January 2018

We investigate the impact of a fluorine plasma treatment used to obtain enhancement-mode operation on the structure and chemistry at the nanometer and atomic scales of an InAlN/GaN field effect transistor. The fluorine plasma treatment is successful in that enhancement mode operation is achieved with a +2.8 V threshold voltage. However, the InAlN barrier layers are observed to have been damaged by the fluorine treatment with their thickness being reduced by up to 50%. The treatment also led to oxygen incorporation within the InAlN barrier layers. Furthermore, even in the as-grown structure, Ga was unintentionally incorporated during the growth of the InAlN barrier. The impact of both the reduced barrier thickness and the incorporated Ga within the barrier on the transistor properties has been evaluated theoretically and compared to the experimentally determined two-dimensional electron gas density and threshold voltage of the transistor. For devices without fluorine treatment, the two-dimensional electron gas density is better predicted if the quaternary nature of the barrier is taken into account. For the fluorine treated device, not only the changes to the barrier layer thickness and composition, but also the fluorine doping needs to be considered to predict device performance. These studies reveal the factors influencing the performance of these specific transistor structures and highlight the strengths of the applied nanoscale characterisation techniques in revealing information relevant to device performance.
LES of supersonic minimal channel flow between isothermal walls at different temperatures including thermal radiation effects using a fictitious gray gas
Authors: Baro Utpal , Mahapatra Susila , Ghosh Somnath , Friedrich Rainer
Published: January 2018

Large-eddy simulation of a supersonic channel flow between isothermal walls at different temperatures is performed to study radiation effects using a fictitious gray gas model. The simulations are carried out at two different resolutions to ascertain the effects of subgrid scales on radiation. Effects of radiation on the mean temperature, on RMS temperature fluctuations as well as on the turbulence structure are presented. For the moderate optical thickness of the flow considered here, the effects of subgrid scales on the radiative heat transfer are found to be small.
Impact ionisation in Al0.9Ga0.1As0.08Sb0.92 for Sb-based avalanche photodiodes
Authors: Collins X. , Craig A. P. , Roblin T. , Marshall A. R. J.
Published: January 2018

We report the impact ionisation coefficients of the quaternary alloy Al0.9Ga0.1As0.08Sb0.92 lattice matched to GaSb substrates within the field range of 150 to 550 kV cm−1 using p-i-n and n-i-p diodes of various intrinsic thicknesses. The coefficients were found with an evolutionary fitting algorithm using a non-local recurrence based multiplication model and a variable electric field profile. These coefficients indicate that an avalanche photodiode not only can be designed to be a function in the mid-wave infrared but also can be operated at lower voltages. This is due to the high magnitude of the impact ionisation coefficients at relatively low fields compared to other III–V materials typically used in avalanche multiplication regions.
Symmetry breaking induced by the parity change in global electromagnetic ion temperature gradient modes
Authors: Kaang Helen H. , Kim S. S. , Jhang Hogun , Kim Juhyung
Published: January 2018

We perform a computational study of the effects of finite plasma β(= plasma thermal energy/magnetic energy) on the residual stress in the context of the quasi-linear theory. The five-field electromagnetic (EM) toroidal ion temperature gradient (ITG) model is considered in the realistic tokamak geometry. Analyses show that the residual stress significantly increases and its radial profile changes from a dipolar to a unipolar shape with increasing β. The change in the mode parity is found to be responsible for the enhancement and the profile change of the residual stress driven by the global EM toroidal ITG mode. This finding highlights the importance of the global eigenmode structure in determining the radial profile of the residual stress.
Preparation of Nd-Fe-B/α-Fe nano-composite thick-film magnets on various substrates using PLD with high laser energy density above 10 J/cm2
Authors: Nakano M. , Kondo H. , Yamashita A. , Yanai T. , Itakura M. , Fukunaga H.
Published: January 2018

PLD (Pulsed Laser Deposition) method with high laser energy density (LED) above 10 J/cm2 followed by a flash annealing enabled us to obtain isotropic nano-composite thick-film magnets with (BH)max ≧ 80 kJ/m3 on polycrystalline Ta substrates. We also have demonstrated that a dispersed structure composed of α-Fe together with Nd2Fe14B phases with the average grain diameter of approximately 20 nm could be formed on the Ta substrates. In this study, we tried to enhance the (BH)max value by controlling the microstructure due to the usage of different metal based substrates with each high melting point such as Ti, Nb, and W. Although it was difficult to vary the microstructure and to improve the magnetic properties of the films deposited on the substrates, we confirmed that isotropic thick-film magnets with (BH)max ≧ 80 kJ/m3 based on the nano-dispersed α-Fe and Nd2Fe14B phases could be obtained on various metal substrates with totally different polycrystalline structure. On the other hand, the use of a glass substrate lead to the deterioration of magnetic properties of a film prepared using the same preparation process.
Observation of magnetization reversal behavior in Sm0.9Gd0.1Cr0.85Mn0.15O3 orthochromites
Authors: Panwar Neeraj , Joby Jostin P. , Kumar Surendra , Coondoo Indrani , Vasundhara M. , Kumar Nitu , Palai Ratnakar , Singhal Rahul , Katiyar Ram S.
Published: January 2018

Impact of co-doping (Gd and Mn) on the magnetic properties has been systematically investigated in SmCrO3 compound. For the synthesized compound Sm0.9Gd0.1Cr0.85Mn0.15O3 (SGCMO), below the Neel transition temperature and under low applied magnetic field, temperature induced magnetization reversal at 105 K (crossover temperature) was noticed in the field cooled magnetization curve. Magnetization reversal attained maximum value of -1.03 emu/g at 17 K where spin reorientation occurred. The magnetization reversal disappeared under higher applied field. From the M-H plots an enhancement in the magnetization was observed due to Gd doping. Magnetocaloric effect at low temperatures measured through the magnetic entropy change was found sixteen times higher for this compound as compared to pristine SmCrO3 and twice to that of SmCr0.85Mn0.15O3 compound. The study reveals the importance of co-doping in tailoring the magnetic properties of rare-earth chromites.
Anisotropic magnetocaloric effect in HoAlGa polycrystalline compound
Authors: Yan Zhang , Xinqi Zheng , JieFu Xiong , Shulan Zuo , Qiaoyan Dong , Tongyun Zhao , Baogen Shen
Published: January 2018

In this work, a nonnegligible anisotropic magnetocaloric effect (MCE) in HoAlGa polycrystalline compounds has been observed. With temperature increasing, the HoAlGa compound undergoes two kinds of magnetic transitions at 19 K and 31 K, respectively, the later has been recognized as an ordinary antiferromagnetic to paramagnetic (AFM-PM) transition. The -ΔS peak of HoAGa reaches 5.4 J/kg K and 1.5 J/kg K at 35 K along parallel and perpendicular texture directions respectively, for a field change of 0-5 T. The result indicates that the HoAlGa polycrystalline compounds with excellent anisotropic MCE can be expected to have effective magnetic refrigeration applications in low temperature range.
Nitrogen doping effect on flow-induced voltage generation from graphene-water interface
Authors: Okada Takeru , Kalita Golap , Tanemura Masaki , Yamashita Ichiro , Meyyappan M. , Samukawa Seiji
Published: January 2018

Liquid-flow-induced generation of electricity using nanocarbons, particularly graphene-water interface, has received attention for energy harvesting. Here, we have obtained voltage generation from a single water droplet motion on graphene. We have investigated the effect of the graphene surface condition on flow-induced voltage generation, which is controlled by heteroatom doping. Nitrogen-doped graphene shows three times higher voltage generation compared to pristine graphene due to the doping-induced surface charge of graphene. Graphene surface potential tuning by doping is shown to play an important role in voltage generation.
The corrosion mechanism of the sintered (Ce, Nd)-Fe-B magnets prepared by double main phase and single main phase approaches
Authors: Shi Xiaoning , Zhu Minggang , Zhou Dong , Song Liwei , Guo Zhaohui , Li Jia , Li Wei
Published: January 2018

The sintered (Ce, Nd)-Fe-B magnets were produced widely by Double Main Phase (DMP) method in China as the magnetic properties of the DMP magnets are superior to those of single main phase (SMP) magnets with the same nominal composition. In this work, the microstructure and corrosion mechanism of the sintered (Ce0.2Nd0.8)30FebalB (wt.%) magnets prepared by DMP and SMP method were studied in detail. Compared to SMP magnets, the DMP magnets have more positive corrosion potential, lower corrosion current density, larger electron transfer resistance, and lower mass loss of the free corrosion experiment in 0.5mol/l Na2SO4 aqueous solution. All of the results show that the DMP magnets have better corrosion resistance than SMP magnets. The back scattered electron images show that the crystalline grains of the DMP magnets are sphericity with a smooth surface while the SMP ones have plenty of edges and corners. Besides, the distribution of Ce/Nd is much more uneven in both magnetic phase and rare earth (Re)-rich phase of the DMP magnets than those of SMP magnets. After corrosion, DMP magnets show eroded magnetic phase and intact Re-rich phase, which indicate that galvanic corrosion of the Re-rich phase acting as the cathode appears.
Novel behaviors of anomalous Hall effect in TbFeCo ferrimagnetic thin films
Authors: Ando Ryo , Komine Takashi , Sato Shiori , Kaneta Shingo , Hara Yoshiaki
Published: January 2018

We investigate the temperature dependence and the thickness dependence of anomalous Hall effect (AHE) of TbFeCo ultra-thin films under high magnetic field. The sign change on temperature dependence of AHE in 20nm-thick TbFeCo film with rare-earth (RE) rich composition was observed. The AHE sign at low temperature is negative while it gradually becomes positive as the temperature increases. Moreover, the AHE sign for 5nm-thick TbFeCo film remains positive while that for 50nm-thick TbFeCo film remains negative at temperature in the range from 5 K to 400 K. The similar thickness dependence of AHE in TM-rich samples was also observed. From the mean-field approximation, the sign change temperature in AHE is related to the compensation temperature and the existence of interfacial region, which has the TM-rich composition and the weak anisotropy. Therefore, We clarified that the novel behavior of AHE sign changes in TbFeCo thin films with different thickness can be explained by the interfacial layer with weak anisotropy and two phase model.
Direct variational determination of the two-electron reduced density matrix for doubly occupied-configuration-interaction wave functions: The influence of three-index N-representability conditions
Authors: Alcoba Diego R. , Torre Alicia , Lain Luis , Massaccesi Gustavo E. , Oña Ofelia B. , Honoré Eduardo M. , Poelmans Ward , Van Neck Dimitri , Bultinck Patrick , De Baerdemacker Stijn
Published: January 2018

This work proposes the variational determination of two-electron reduced density matrices corresponding to the ground state of N-electron systems within the doubly occupied-configuration-interaction methodology. The P, Q, and G two-index N-representability conditions have been extended to the T1 and T2 (T2′) three-index ones and the resulting optimization problem has been addressed using a standard semidefinite program. We report results obtained from the doubly occupied-configuration-interaction method, from the two-index constraint variational procedure and from the two- and three-index constraint variational treatment. The discussion of these results along with a study of the computational cost demanded shows the usefulness of our proposal.
Lithium doping and photoluminescence properties of ZnO nanorods
Authors: Shakti Nanda , Devi Chandni , Patra A. K. , Gupta P. S. , Kumar Sandeep
Published: January 2018

This article presents a comprehensive experimental study of optical properties of Li-doped ZnO nanorods grown by a low temperature (300 °C) thermal decomposition method. In particular, a study of the room temperature photoluminescence spectra dependence on the Li concentration is presented here. The doping of Li in ZnO nanorods results in a redshift in near band edge emission (NBE) compared to the undoped ZnO nanorods. Depending on the Li concentration, we observe a green emission in Photoluminescence spectra. The possible physical mechanisms governing the visible region luminescence are also discussed. These results show that Li-doped ZnO nanorods with strong visible region luminescence have potential applications in optoelectronic devices.
Unravelling radiative energy transfer in solid-state lighting
Authors: Melikov Rustamzhon , Press Daniel Aaron , Ganesh Kumar Baskaran , Sadeghi Sadra , Nizamoglu Sedat
Published: January 2018

Today, a wide variety of organic and inorganic luminescent materials (e.g., phosphors, quantum dots, etc.) are being used for lighting and new materials (e.g., graphene, perovskite, etc.) are currently under investigation. However, the understanding of radiative energy transfer is limited, even though it is critical to understand and improve the performance levels of solid-state lighting devices. In this study, we derived a matrix approach that includes absorption, reabsorption, inter-absorption and their iterative and combinatorial interactions for one and multiple types of fluorophores, which is simplified to an analytical matrix. This mathematical approach gives results that agree well with the measured spectral and efficiency characteristics of color-conversion light-emitting diodes. Moreover, it also provides a deep physical insight by uncovering the entire radiative interactions and their contribution to the output optical spectrum. The model is universal and applicable for all kinds of fluorophores.
On the mechanical stability of the body-centered cubic phase and the emergence of a metastable cI16 phase in classical hard sphere solids
Authors: Warshavsky Vadim B. , Ford David M. , Monson Peter A.
Published: January 2018

The stability of the body-centered cubic (bcc) solid phase of classical hard spheres is of intrinsic interest and is also relevant to the development of perturbation theories for bcc solids of other model systems. Using canonical ensemble Monte Carlo, we simulated systems initialized in a perfect bcc lattice at various densities in the solid region. We observed that the systems rapidly evolved into one of four structures that then persisted for the duration of the simulation. Remarkably, one of these structures was identified as cI16, a cubic crystalline structure with 16 particles in the unit cell, which has recently been observed experimentally in lithium and sodium solids at high pressures. The other three structures do not exhibit crystalline order but are characterized by common patterns in the radial distribution function and bond-orientational order parameter distribution; we refer to them as bcc-di, with i ranging from 1 to 3. We found similar outcomes when employing any of the three single occupancy cell (SOC) restrictions commonly used in the literature. We also ran long constant-pressure simulations with box shape fluctuations initiated from bcc and cI16 initial configurations. At lower pressures, all the systems evolved to defective face-centered cubic (fcc) or hexagonal close-packed (hcp) structures. At higher pressures, most of the systems initiated as bcc evolved to cI16 with some evolving to defective fcc/hcp. High pressure systems initiated from cI16 remained in that structure. We computed the chemical potential of cI16 using the Einstein crystal reference method and found that it is higher than that of fcc by ∼0.5kT–2.5kT over the pressure range studied, with the difference increasing with pressure. We find that the undistorted bcc solid, even with constant-volume and SOC restrictions applied, is so mechanically unstable that it is unsuitable for consideration as a metastable phase or as a reference system for studying bcc phases of other systems. On the other hand, cI16 is a mechanically stable structure that can spontaneously emerge from a bcc starting point but it is thermodynamically metastable relative to fcc or hcp.