bluuebunny/crossref_metadata_2025 huggingface dataset:
Modelling and simulation for UAV‐aided vehicular MIMO communication channels
Authors: Li Yiran , Cheng Xiang
Published: August 2019

For the unmanned aerial vehicle (UAV)‐aided vehicular multiple‐input multiple‐output Ricean fading channel, this study proposes a novel three‐dimensional geometry‐based stochastic model (GBSM). This model is the first GBSM for UAV‐aided vehicular communication channels with the ability to investigate channel characteristics in different vehicular traffic density (VTD) scenarios, which is a combination of a single‐cylinder model and an elliptic‐cylinder model, and the signal is a sum of the line‐of‐sight component, single‐bounced, and double‐bounced rays. In addition, some expressions of channel statistical properties are derived, including space–time correlation function, space‐Doppler spectral power density, envelope level crossing rate, and average fade duration. Based on the reference model, corresponding deterministic and stochastic simulation models are developed. Finally, the authors further explore the impact of some unique UAV‐related parameters and different VTDs on channel statistics, and get some useful conclusions based on numerical results.
Determining the appropriate lane width at urban signalised intersections – a case study in Beijing
Authors: Chang Xin , Li Haijian , Rong Jian , Chen Xiaoxuan , Wang Yi
Published: August 2019

Intersections are the key nodes in an urban traffic network that affect overall traffic efficiency. Lane width is a major element of an intersection that is affected by the saturation flow rate of the intersection. It is also influenced by a variety of other factors, such as road resource constraints, vehicle composition, traffic safety, and driving comfort. To determine the appropriate lane width, this study analysed relationships between lane widths and design‐related factors, including saturation flow rate, lateral safety distance, traffic crash rate, and driver comfort. First, screening and surveys were conducted using the design data of more than 3000 existing crossroads. Then, seven intersections with different lane widths were selected. To collect traffic flow data, video‐based surveys were conducted. Meanwhile, the traffic crash rate was collected to assess traffic safety. Moreover, surveys were conducted to assess the driving experience. Finally, the Delphi method was developed to evaluate the index weights of the design‐related factors. The case study revealed that the optimal lane width for four‐legged intersections is 3.1 m. A lane width of 2.8 m is an alternative for cases of limited road resources. The results could be supplementary guidance or reference for road designers and administrators.
Hierarchical control system for a flexible microgrid with dynamic boundary: design, implementation and testing
Authors: Yin He , Ma Yiwei , Zhu Lin , Hu Xiaotong , Su Yu , Glass Jim , Wang Fred , Liu Yilu , Tolbert Leon M.
Published: August 2019

The design, implementation, and testing of a control system for a flexible microgrid (MG) is presented in this study. The MG controllers can be implemented in a real‐world MG with multiple smart switches, photovoltaic panel system, and battery energy storage systems (BESSs). With the benefits from smart switches, the MG has unique characteristics such as dynamic boundary and flexible point of interconnection (POI) concepts. To control such a unique MG and realise the dynamic boundary, an MG central controller and two types of local controllers are implemented. Compared to the MG with fixed boundary, the MG with dynamic boundary can have smaller BESS capacity, better utilisation of renewable energy, and multiple POI options. Also, compared with IEEE Std 2030.7–2017, the topology identification and active and reactive power balance functions are newly designed to realise the dynamic boundary concept. The planned islanding and reconnection functions are modified to realise the flexible POI concept. These functions are introduced including the software architecture, cooperation, and interaction among them. Finally, a hardware‐in‐the‐loop testing platform based on the Opal‐RT real‐time simulator is set up to verify the performance, realisation of the dynamic boundary, and flexible POI concepts with four comprehensive test scenarios.
Monopulse forward‐looking imaging algorithm based on Levenberg–Marquardt optimisation
Authors: Zhou Tao , Pang Bo , Dai Dahai , Wu Hao , Wang Xuesong
Published: August 2019

With precise angle measurement, traditional monopulse techniques for forward‐looking imaging can acquire exact angle information of one single target within a radar beam. However, when multiple targets exist in a beam, it is difficult to resolve them. To address this problem, a novel monopulse forward‐looking imaging algorithm based on Levenberg–Marquardt (LM) optimisation is proposed. The core idea of this algorithm is to solve maximum likelihood estimation problem based on LM optimisation (ML‐LM) to obtain the direction of arrival (DOA) estimation of unresolved targets. First, the echo model of two targets within a forward‐looking radar beam is established, then the imaging framework of the proposed algorithm is introduced. Finally, the advantages of ML‐LM are illustrated based on a series of evaluation criterion, including angle measurement error for various values of signal‐to‐noise ratio (SNR), angle interval adaptability and computational efficiency. The simulation results show that two targets within a forward‐looking radar beam can be resolved and relocated accurately utilising the proposed algorithm. Meanwhile, the comparison with other algorithms shows it has higher DOA estimation accuracy, less computational complexity and a wider range of angle interval adaptability.
WiFi‐based imaging for ground penetrating radar applications: fundamental study and experimental results
Authors: Feng Weike , Friedt Jean‐Michel , Hu Zhipeng , Cherniak Grigory , Sato Motoyuki
Published: August 2019

As a fundamental research step for subsurface target imaging by passive ground penetrating radar, some simulation and experimental results of passive bistatic radar imaging for short‐range targets by using IEEE 802.11 Wireless Fidelity (WiFi) wave as the source of illumination have been presented. As the WiFi signal only penetrates shallow layers and yet lacks bandwidth for high resolution subsurface structure mapping, the interrogation of cooperative targets with the passive bistatic radar approach is demonstrated. This strategy is achieved by inserting surface acoustic wave (SAW) delay lines acting as dedicated reflectors allowing for subsurface tagging (identification) or sensing (temperature measurement) through the fine measurement of echo delays. Experimental results show that short‐range targets, such as cars and metallic plates located within 10 m, can effectively be detected and imaged. The response of the SAW delay lines can also be well probed.
Robust adaptive beamforming with mainlobe maintenance of monopulse beams
Authors: Fernández Manuel F. , Yu Kai‐Bor
Published: August 2019

Adaptive monopulse approaches for angularly localising a main‐beam target in jamming are usually based on variations of the concept of optimising the sum (Σ) beam via standard adaptation and then optimising the delta (Δ) beam subject to maintain the monopulse slope. These methods have some deficiencies: they do not address target self‐nulling issues; they lack tapering, leading to high sidelobes; they introduce multiple point constraints, which may result in target leakage; and they assume linearity of the monopulse ratio curve, something valid only in a small region close to the beam steering direction. The method of this study addresses these and other concerns by maintaining tapered Σ and Δ beams and fully preserving their mainlobes while adaptively suppressing jammers. This approach provides the added bonus of enabling operating in the monopulse curve's non‐linear region at wider beamwidths, hence also increasing the efficiency of radar searching and tracking functions. It is shown that such approach is extremely robust and flexible, as it avoids target self‐nulling effects due to beam mispointing, it is immune to target and interference dithering effects, and it can be easily extended for super‐resolving multiple main‐beam targets.
δ‐GLMB filter based on DI in a clutter
Authors: Peng Hua‐fu , Huang Gao‐ming , Tian Wei , Qiu Hao
Published: August 2019

For the problem that the performance of existing multi‐target tracking algorithm's serious degrades in a dense clutter environment, a novel Doppler information assistant δ‐ generalised labelled multi‐Bernoulli (DI‐δ‐ GLMB) filter is proposed. By introducing DI, a new measurement likelihood function is established, and the improved update equation based on the δ‐ GLMB filter framework is derived. In addition, a sequential Monte Carlo implementation method is given under the non‐linear model. Simulation results show that compared with the DI probability hypothesis density filter and the standard δ‐ GLMB filter, the estimation of the proposed algorithm is more accurate and stable.
Simulation and analysis system of sea echo based on MATLAB
Authors: Fengjun Yan , Xinzhe Sun
Published: August 2019

Marine radar is mainly used for maritime navigation and avoidance of collision. Shore‐based marine radar is used for offshore vessel management. In the marine environment, the radar echo is complex for the targets which are polytypic and undulant, and the clutter is strongly and violently affected by the environment. In order to simulate and analyse the sea echo from shore‐based radar with real time and high precision, this study sets up a kind of MATLAB simulation and analyses system of real‐time data communication and record playback based on transport control protocol/ Internet protocol and GUI. The system can realise the multi‐dimensional multi‐mode display and subsequent refined simulation of the echo based on static data or dynamic data, and the situation analysis of marine environment is provided through the learning training of multi‐frame data. The system has been successfully applied in field experiments and has played an important role in fault analysis and algorithm optimisation, which has very high application value.
Multi‐static airborne passive SAR imaging using cross‐validation‐based SOMP algorithm
Authors: Qu Lele , Liu Yu , An Shimiao , Yang Tianhong , Sun Yanpeng
Published: August 2019

The availability of multiple illuminators in the multi‐static airborne passive synthetic radar (SAR) system can provide the improved SAR imaging capability. The reflection coefficients of targets in the observed scene are different due to diverse observation angles and carrier frequencies in multi‐static scenarios. To tackle this problem, the study firstly introduces the forward signal model of multi‐static airborne passive SAR system and then formulates the imaging problem as an joint sparsity optimisation problem of multiple measurement vectors. Under the distributed greedy sparse recovery framework, the study finally proposes the cross‐validation‐based simultaneous orthogonal matching pursuit (SOMP) imaging algorithm for multi‐static airborne passive SAR system. The proposed imaging algorithm can avoid the requirement of sparsity level of the observed scene and achieve the accurate imaging reconstruction of the observed scene. The simulation results have verified the effectiveness and validity of the proposed imaging method.
Characterization of high-precision resistive voltage divider and buffer amplifier for ac voltage metrology
Authors: Karlsen Bjørnar , Lind Kåre , Malmbekk Helge , Ohlckers Per
Published: August 2019

A high-precision voltage buffer and a 10:1 resistive voltage divider have been constructed for use in ac voltage and electrical power metrology. Long-term stability of the buffer's dc response has been demonstrated by two dc sweeps performed 20 days apart, with best-fit linearized gain varying less than 1 μV/V. The absolute ac gain has been measured using a high-precision digital multimeter for 10 Hz and 1 kHz with results consistent with dc within 5 μV/V. This value agrees with the characterization of ac–dc difference using thermal converters from different producers with a variety of resistance for various voltages from 1 V to 5 V. The ac–dc difference was further characterized better than 40 μV/V for the same voltages up to 100 kHz and better than 100 μV/V for 3 V at 1 MHz. Absolute ac gain and ac–dc difference has also been measured for the voltage divider and buffer combination from 10 V to 50 V, with similar agreement up to 1 kHz. The ac–dc difference from 10 Hz to 100 kHz of this combination shows an agreement well within 30 μV/V in this entire voltage span with a total response not exceeding 125 μV/V. This make the voltage divider and buffer combination suitable for sampling electrical powers for a wide range of voltages.
Neue Ideen für mehr Gesundheit
Authors: Dragano Nico , Moebus Susanne
Published: August 2019

Es ist Aufgabe der Wissenschaft nach Neuem zu suchen, warum also auf einem wissenschaftlichen Kongress explizit auf „das Neue“ schauen? Zunächst einmal kann es erhellend sein, von Zeit zu Zeit, das eigene Tun zu hinterfragen und zu diskutieren, ob das, was wir in Forschung, Lehre und Praxis vertreten, wirklich originell ist. Die Gesundheitsforschung hat in den vergangenen Jahrzehnten unzweifelhaft wichtige und erfolgreiche Beiträge zum Verständnis und zur Verbesserung der Bevölkerungsgesundheit geleistet. Es wurden, um nur Beispiele zu nennen, a) die großen gesundheitlichen Probleme unserer Zeit empirisch beschrieben, b) umfassende theoretische Modelle der Bevölkerungsgesundheit entwickelt, c) neue Methoden der Datensammlung und -analyse erarbeitet sowie d) Interventionen konzipiert, die die Gesundheit aller Menschen fördern sollen.
Steroidinduzierter Diabetes mellitus: Wie erkennen – wie behandeln?
Authors: Jungmann Eckart
Published: August 2019

Geschätzt werden in Deutschland etwa 1 Million Patienten mit Glukokortikoiden behandelt. Etwa jeder Zehnte entwickelt einen Steroiddiabetes, dessen Entstehung durch verschiedene Risikofaktoren begünstigt werden kann. Außerdem hängt das Risiko einer Diabetesentwicklung von der Glukokortikoiddosierung ab, bei systemischer Therapie ist das Risiko höher als bei lokaler. Auch die topische Glukokortikoidanwendung schließt eine Diabetesentwicklung als unerwünschte Arzneimittelwirkung jedoch nicht aus. Die Entwicklung eines Steroiddiabetes ist auch Symptom des seltenen Cushing-Syndroms. Besteht ein klinischer Verdacht auf das Vorliegen dieses endogenen Hyperkortisolismus, sollte die Diagnostik und Differenzialdiagnostik des Cushing-Syndroms durch laborchemische Screeningtests begonnen werden, unerkannt hat das Cushing-Syndrom eine hohe Morbidität und Mortalität. Bei der Glukokortikoidtherapie mit unphysiologischen Glukokortikoiddosierungen von über 5 mg Prednisolonäquivalent täglich resultiert daraus eine zunehmende Insulinresistenz mit der Folge der hyperglykämischen Entgleisung. Aktuelle Studien erlauben genauere Einblicke in die intrazellulären Kortisoleffekte. Die Diabetesdiagnose wird nach den üblichen Kriterien gestellt. Bei Patienten mit nachgewiesener Glukosetoleranzstörung ist ebenso wie bei Patienten ohne vorbestehenden Diabetes zunächst eine Schulung erforderlich, eine orale Diabetestherapie mit Metformin oder auch Dipeptidylpeptidase (DPP)-4-Hemmern kann hilfreich sein, unter Umständen wird eine Insulinbehandlung notwendig. Bei Patienten mit bekanntem und bereits behandeltem Diabetes ist die Therapie zu eskalieren. Eine zusätzliche Insulintherapie ist zumeist erforderlich, vorherige Insulinmengen müssen um bis zu 100 % gesteigert werden. Wegen der vordergründig postprandialen Hyperglykämie wird die Zugabe von prandialem Humaninsulin gegenüber einem Basalinsulin bevorzugt. Risikofaktoren für die Entwicklung einer Hypoglykämie sind ebenfalls zu berücksichtigen. Es kann nicht durchgängig davon ausgegangen werden, dass die Entwicklung eines steroidinduzierten Diabetes reversibel ist, eine entsprechende Aufklärung der Patienten ist erforderlich.
68Ga-RM2 PET in PSMA- positive and -negative prostate cancer patients
Authors: Hoberück Sebastian , Michler Enrico , Wunderlich Gerd , Löck Steffen , Hölscher Tobias , Froehner Michael , Braune Anja , Ivan Platzek , Seppelt Danilo , Zöphel Klaus , Kotzerke Jörg
Published: August 2019

﻿Aim 68Ga-PSMA-11 is the gold standard for molecular imaging of prostate cancer. However, recurrent tumor manifestations or metastases cannot be detected in every case. Therefore, we investigated if there is an additive value of the gastrin-releasing peptide receptor (GRP-R) ligand 68Ga-RM2 compared to the well-established 68Ga-PSMA-11 in patients with (Group 1) and without (Group 2) pathologic PSMA-expression in different tumor stages.

Patients and Methods Sixteen men (median age: 74 years, range 50–80 years) with prostate cancer in different stages who had a recent negative (n = 8) or pathologic (n = 8) PSMA PET underwent a subsequent 68Ga-RM2 PET. Both examinations were analyzed qualitatively and quantitatively and compared in terms of pathologic and physiologic tracer distribution.

Results None of the PSMA-negative patients showed any pathological RM2-accumulation. Pathologic PSMA-uptake was observed in 8 patients of whom 5 had pathologic RM2-uptake. The number of patients with a local recurrence was equal in both scans (n = 3). Bone metastases and lymph node metastases were detected in less patients in RM2 PET compared to PSMA PET (n = 4 vs. 7 and n = 2 vs. 5, respectively). In one patient, PSMA-positive liver metastases were not detected in RM2. RM2 PET revealed two additional lesions indicative for bone metastases in two patients with multiple PSMA-positive bone metastases, which had no therapeutic consequence.

Conclusion At least in our small and heterogeneous patient population, 68Ga-RM2 showed no clinically relevant, additional benefit compared to 68Ga-PSMA-11 PET.
Type VI Choledochal Cysts—Case Report and Review of Literature
Authors: Amarjothi J. M. V. , Ramasamy Villalan , Jesudasan Jeyasudhahar , NaganathBabu O. L.
Published: August 2019

Choledochal cysts (CDC), are rare congenital dilations involving the extra hepatic biliary apparatus with or without dilation of the intrahepatic bile ducts. They are conventionally classified into five types. A new type, type VI, causing dilation of the cystic duct between the neck of the gall bladder and the common hepatic duct (CHD) has been described in medical literature which is the rarest of all these subtypes. They are commonly observed in middle aged females and are mostly symptomatic. Most of these cysts need magnetic resonance cholangiopancreatography (MRCP) for accurate diagnosis. Treatment options for these lesions are not well defined but range from simple cholecystectomy to complete excision of the entire bile duct and biliary reconstruction, as there is a concern of malignant transformation in these cysts. Hence, these rare cysts, though rare, must be borne in mind when dealing with suspicious cystic lesions in the biliary tract. Here, we present an interesting case of such a rare cyst and its management in a middle aged woman.
Preliminary Development of Solid Dispersion for an Insoluble Compound ZL006 by Miniaturized Hot Melt Extrusion
Authors: Zhang Lijun , Luan Hansen , Lu Weiyue , Wang Hao
Published: August 2019

The purpose of this study was to develop a solid dispersion (SD) by miniaturized hot-melt extrusion (HME) for an insoluble molecule ZL006 which showed potency of increasing leukocytes. A preliminary formulation screening was conducted using solvent evaporation method. The selected SD formulation was further optimized and scaled up using a miniaturized twin-screw extruder. Solid-state characterizations of the scale-up SD and its corresponding physical mixture (PM) were performed by X-ray powder diffraction (XRPD), modulated differential scanning calorimetry (mDSC), and Fourier's transform infrared spectroscopy (FTIR). XRPD and mDSC results indicated the formation of amorphous SD. FTIR spectrum indicated the possible hydrogen bond formation between the compound and the excipient. A discriminating non-sink condition micro-dissolution of SD showed the fast release of ZL006 which was approximately two-fold and three-fold of dissolution of PM and pure crystalline compound, respectively. The preliminary in vivo pharmacokinetics (PK) study in rats showed 71% oral bioavailability from the SD, while the bioavailability of ZL006 conventional suspension was less than 1%. Thus, an SD formulation for ZL006 with improved solubility and bioavailability was developed by miniaturized HME with minimal amount of compound at early preclinical stage, which could enable the preclinical evaluation.
A power output and mechanical model of a wind turbine and its control strategy under severe wind conditions
Authors: Lin Xiangning , Wang Zhixun , Ding Suyang , Zhang Zheyuan , Li Zhengtian
Published: August 2019

Under the current wind turbine control strategy, wind turbines are cut off to guarantee their safety for wind speeds exceeding 25 m/s. However, under severe wind conditions, power grids with high wind power penetration will suffer a catastrophic consequence due to the large-scale cut-off of wind turbines. To solve the problem, mechanical effects on a wind turbine from the aspect of airflow are analyzed in this paper; a numerical connection between the thrust coefficient and the wind power coefficient is proposed. On the basis of those analyses, the accumulated load on the blades and the tower of the wind turbine are analyzed, and a cohesive control strategy is proposed. The strategy uses real-time wind speed data to calculate the mechanical load on a wind turbine and realizes the maximum active power output under severe wind conditions. The results of case studies verify the effectiveness and superiority of the proposed strategy.
Friction pressure drop model of gas-liquid two-phase flow in an inclined pipe with high gas and liquid velocities
Authors: Liu Zilong , Liao Ruiquan , Luo Wei , Ribeiro Joseph X. F. , Su Yubin
Published: August 2019

The calculations of friction pressure drop is the most complicated in multiphase flow. Understanding of the friction pressure drop in pipes are of great importance for many industry problems. The existing friction pressure drop models are generally based on low gas and liquid velocities in horizontal and vertical pipes. In this paper, a two-phase flow experiment in inclined pipe was performed. We report the effect of superficial gas and liquid velocities on friction pressure drop, the results indicate that the pressure drop increases with the increase in superficial gas velocity and superficial liquid velocity. According to the experimental analysis and assuming that the fluid in contact with the pipe wall at high velocity is in a liquid phase, we developed a new friction pressure drop model of different flow pattern. This model based on the correlation between the fraction factor and the superficial gas and superficial liquid Reynold numbers. Compared with the previous models, the predictive performance of the present model is good and remains basically stable.
Atomic structure and electronic properties of lead and tin based hybrid halide perovskite surface for photovoltaic applications
Authors: Khanal Rabi , Ayers Nicholas , Banerjee Soumik , Choudhury Samrat
Published: August 2019

Organic-inorganic hybrid halide perovskites are emerging as one of the potential materials in the photovoltaic community due to its attractive power conversion efficiency and cost-effective device fabrication. The photovoltaic performance of hybrid halide perovskite is linked to its atomic and electronic structure at the surface. Here we have used electronic structure calculations to determine the structural and electronic properties at the surface of MABX3 (MA = CH3NH3; B = Sn or Pb; X= I, Br, or Cl) perovskites. Next, we compared calculated electronic properties of the surface with the corresponding bulk values. Our results reveal that the structural properties like B-X distances, B-X-B angles, and orientation of MA are different between bulk to perovskite surface. Such changes in structural features at the perovskite surface lead to change in the band gap between surface and bulk perovskite. Both structural features and the band gap at the surface are found to be dependent on the crystal symmetry and chemistry of the perovskite. Further, for all perovskite compositions investigated, no midgap surface electronic states were observed.
Comparative studies of total-variation-regularized sparse reconstruction algorithms in projection tomography
Authors: Xie Hui , Wang Huiyuan , Wang Lin , Wang Nan , Liang Jimin , Zhan Yonghua , Chen Xueli
Published: August 2019

Projection tomography techniques, such as optical projection tomography and stimulated Raman projection tomography, can efficiently provide quantitative distributions of compositions in three-dimensional volumes that are isotropic and exhibit high spatial resolutions. A projection model and a reconstruction algorithm are two important elements of such techniques. This research explores the quality vs. efficiency tradeoffs for combinations of existing algorithms in a performance study. Two projection models are used. This first is the pixel vertex driven projection model; and the second is the distance driven projection model (DDM). These models are integrated with three TV-regularized iterative reconstruction algorithms: the algebraic reconstruction technique, the simultaneous algebra reconstruction technique (SART), and the two-step iterative shrinkage/thresholding algorithm. The performance of the combinations of these projection models and reconstruction algorithms are evaluated with a sparsely sampled data set in simulation experiments. The experiments consider both the reconstruction image quality and the time complexity. The comparative results indicate the combination of the SART and DDM algorithms provide a good balance between the quality and efficiency of reconstructed images. The exploratory results of this study are expected to provide some useful guidance on algorithmic development and applications in the projection tomography field.
Unraveling the proteins that cause neurodegenerative diseases
Authors: Kish Stacy W.
Published: August 2019

Researchers identify particles that prevent clustering in the proteins responsible for neurodegenerative conditions, like Parkinson’s disease.
Framework for using modern devices in introductory physics courses
Authors: Planinsic Gorazd , Etkina Eugenia
Published: August 2019

In this paper we introduce a practical framework that guides teachers on how to integrate modern devices (MD) into an existing physics course without adding new topics. The framework has three components: using the device as a black box, using the device to learn the physics behind its operation and using the device to learn new physics. We used two devices (a laser distance meter and an LED) to illustrate how to apply this framework in instruction. We provide examples of learning activities and ideas that students bring in when they engage in these activities. We hope that the framework will encourage and help teachers to systematically use MD in their courses in suggested ways.
Experimental implementations of cavity-magnon systems: from ultra strong coupling to applications in precision measurement
Authors: Flower Graeme , Goryachev Maxim , Bourhill Jeremy , Tobar Michael E
Published: August 2019

Several experimental implementations of cavity-magnon systems are presented. First an Yttrium Iron Garnet (YIG) block is placed inside a re-entrant cavity where the resulting hybrid mode is measured to be in the ultra strong coupling (USC) regime. When fully hybridised the ratio between the coupling rate and uncoupled mode frequencies is determined to beg/ω = 0.46. Next a thin YIG cylinder is placed inside a loop gap cavity. The bright mode of this cavity couples to the YIG sample and is similarly measured to be in the USC regime with ratio of coupling rate to uncoupled mode frequencies asg/ω = 0.34. A larger spin density medium such as lithium ferrite (LiFe) is expected to improve couplings by a factor of 1.46 in both systems as coupling strength is shown to be proportional to the square root of spin density and magnetic moment. Such strongly coupled systems are potentially useful for cavity QED, hybrid quantum systems and precision dark matter detection experiments. The YIG disc in the loop gap cavity, is, in particular, shown to be a strong candidate for dark matter detection. Finally, a LiFe sphere inside a two post re-entrant cavity is considered. In past work it was shown that the magnon mode in the sample has a turnover point in frequency (Goryachevet al2018Phys. Rev.B97155129). Additionally, it was predicted that if the system was engineered such that it fully hybridised at this turnover point the cavity-magnon polariton transition frequency would become insensitive to both first and second order magnetic bias field fluctuations, a result useful for precision frequency applications. This work implements such a system by engineering the cavity mode frequency to near this turnover point, with suppression in sensitivity to second order bias magnetic field fluctuations shown.
Enhancing von Neumann entropy by chaos in spin–orbit entanglement*
Authors: Liu Chen-Rong , Yu Pei , Chen Xian-Zhang , Xu Hong-Ya , Huang Liang , Lai Ying-Cheng
Published: August 2019

For a quantum system with multiple degrees of freedom or subspaces, loss of coherence in a certain subspace is intimately related to the enhancement of entanglement between this subspace and another one. We investigate intra-particle entanglement in two-dimensional mesoscopic systems, where an electron has both spin and orbital degrees of freedom and the interaction between them is enabled by Rashba type of spin–orbit coupling. The geometric shape of the scattering region can be adjusted to produce a continuous spectrum of classical dynamics with different degree of chaos. Focusing on the spin degree of freedom in the weak spin–orbit coupling regime, we find that classical chaos can significantly enhance spin–orbit entanglement at the expense of spin coherence. Our finding that classical chaos can be beneficial to intra-particle entanglement may have potential applications such as enhancing the bandwidth of quantum communications.
Mass transfer and possible third-body effect on the period variations of the near-contact binary CN And
Authors: Cai Jin-Ting , Yu Yun-Xia , Hu Ke , Xiang Fu-Yuan
Published: August 2019

We present a period analysis of the near-contact binary CN And using all available times of light minima. It is revealed that the orbital period exhibits a long-term decrease as well as a small-amplitude cyclic oscillation. This result suggests that the secular period decrease at the rate ofdP/dt= −1.4017 × 10−7d yr−1is caused by a combination of mass transfer and angular momentum loss due to magnetic braking. The periodic variation with an amplitude ofA= 0.0036 d and a period ofPmod= 28.3542 yr should be rooted in the light-time effect of a third body, rather than cyclic magnetic activity.
Intra-day variability of three Seyfert galaxies measured with XMM-Newton
Authors: Tripathi Ashutosh , Joseph Wiita Paul , Chandra Gupta Alok , Gu Min-Feng , Liao Mai
Published: August 2019

We present and analyze the variability of three Seyfert galaxies on intra-day timescales. We have analyzed in a uniform manner the 38 longest (>30 ks) observations made for NGC 4051, MCG-06–30–15 and NGC 4151 by XMM-Newton between 2000 and 2015. The nuclei were quite active during essentially all of these observations and the overall X-ray fluxes (0.3–10 keV) varied by an order of magnitude. Most of the observations do appear to show characteristic timescales, estimated through their auto-correlation functions, ranging between ∼2.9 ks and ∼45.3 ks. The hard (2–10 keV) and soft (0.3–2.0 keV) bands are very well correlated but consideration of their hardness ratios shows that the sources typically soften during flares. We also provide new estimates of the central black hole masses for these three AGNs that support the hypothesis that Narrow Line Seyfert 1 galaxies have relatively small central black holes.
Stellar spectral classification and feature evaluation based on a random forest
Authors: Li Xiang-Ru , Lin Yang-Tao , Qiu Kai-Bin
Published: August 2019

With the availability of multi-object spectrometers and the design and operation of some large scale sky surveys, the issue of how to deal with enormous quantities of spectral data efficiently and accurately is becoming more and more important. This work investigates the classification problem of stellar spectra under the assumption that there is no perfect absolute flux calibration, for example, when considering spectra from the Guo Shou Jing Telescope (the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, LAMOST). The proposed scheme consists of the following two procedures: Firstly, a spectrum is normalized based on a 17th order polynomial fitting; secondly, a random forest (RF) is utilized to classify the stellar spectra. Experiments on four stellar spectral libraries show that the RF has good classification performance. This work also studied the spectral feature evaluation problem based on RF. The evaluation is helpful in understanding the results of the proposed stellar classification scheme and exploring its potential improvements in the future.
AstroSat observation of GX 5–1: spectral and timing evolution
Authors: Bhulla Yashpal , Misra Ranjeev , Yadav J S , A Jaaffrey S N
Published: August 2019

We report on the first analysis of an AstroSat observation of the Z-source GX 5–1 on 2017 February 26−27. The hardness-intensity plot reveals that the source traced out the horizontal and normal branches. The 0.8−20 keV spectra from simultaneous SXT and LAXPC data at different locations of the hardness-intensity plot can be described well by disk emission and a thermal Comptonized component. The ratio of the disk flux to the total flux, i.e., the disk flux ratio, increases monotonically along the horizontal branch to the normal one. Thus, the difference between the normal and horizontal branches is that in the normal branch, the disk dominates the flux while in the horizontal one it is the Comptonized component which dominates. The disk flux scales with the inner disk temperature as

T

in

5.5

and not as

T

in

4

, suggesting that either the inner radius changes dramatically or that the disk is irradiated by the thermal component changing its hardness factor. The power spectra reveal a quasi-periodic oscillation (QPO) whose frequency changes from ∼30 Hz to 50 Hz. The frequency is found to correlate well with the disk flux ratio. In the 3−20 keV LAXPC band, the r.m.s. of the QPO increases with energy (r.m.s.

∝

E

0.8

), while the harder X-rays seem to lag the soft ones with a time-delay of milliseconds. The results suggest that the spectral properties of the source are characterized by the disk flux ratio and that the QPO has its origin in the corona producing the thermal Comptonized component.
The diurnal variation of polarization characteristics of the Earth treated as an exoplanet
Authors: Wang Shuang , Qu Zhong-Quan , Li Hao
Published: August 2019

The diurnal polarization variation of the Earth, treated as an exoplanet with an unresolved disk but resolvable from its host star, is presented in three wavelength bands centered at 490 nm, 670 nm and 865 nm respectively according to French satellite-borne PARASOL data. We aim to estimate disk-integrated polarization of the Earth with a phase angle of 55°. It is shown that: (1) the linear polarization signal and its variation are ascribed to the combination of surface feature distribution and atmospheric conditions acting as a variable polarimetric modulator; and (2) the polarimetric wavelength dependence is strong due to the atmospheric wavelength sensitivity. During the period when the PARASOL data were acquired, the cloud coverage ranged from 44.0% to 57.7%, and the polarimetric diurnal variation amplitude was within 1.8% in the 490 nm band, 1.3% in the 670 nm band and 1.5% in the 865 nm band.
The local properties of supernova explosions and their host galaxies
Authors: Zhou Li , Liang Yan-Chun , Ge Jun-Qiang , Shao Xu , Chen Xiao-Yan , Deng Li-Cai
Published: August 2019

We aim to understand the properties at the locations of supernova (SN) explosions in their host galaxies and compare with the global properties of these host galaxies. We use the integral field spectrograph (IFS) of Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) to generate 2D maps of the parameter properties for 11 SN host galaxies. The sample galaxies are analyzed one by one in detail in terms of their properties of velocity field, star formation rate, oxygen abundance, stellar mass, etc. This sample of SN host galaxies has redshifts around

z
∼
0.03

, which is higher than those of previous related works. The higher redshift distribution allows us to obtain the properties of more distant SN host galaxies. Metallicity (gas-phase oxygen abundance) estimated from integrated spectra can represent the local metallicity at SN explosion sites with small bias. All the host galaxies in our sample are metal-rich galaxies (12+

log

(O/H)

>
8.5

) except for NGC 6387, which means SNe may be more inclined to explode in metallicity-rich galaxies. There is a positive relation between global gas-phase oxygen abundance and the stellar mass of host galaxies. We also try to compare the differences of the host galaxies between SNe Ia and SNe II. In our sample, both SNe Ia and SNe II can explode in normal galaxies, but SNe II can also explode in an interacting or a merging system, in which star formation is occurring in the galaxy.
Intelligent Control Approach for Fluid Power Transmission of a Wind Turbine System
Authors: Mungekar Abhishek , Venkatesan Kalaichelvi , Ramanujam Karthikeyan , Savio Lourence Jason
Published: August 2019

Fluid power transmission has caught the eye in recent times, in the field of wind turbine technology. The turbine rotor blades tend to yield an aerodynamic torque, which is transformed into a high pressure fluid through a pump. This fluid is utilized to generate speed and torque yet again at the distant end of the circuit. The paramount objective of this research is to obtain a virtually operating dynamic model of a hydraulic powered transmission in a wind turbine, in order to understand its dynamic behaviour and also, to obtain knowledge about the influence of the prime parameters on the wind turbine. To accomplish this task, a virtual hydraulic powered wind turbine system is designed with a power rating of 23KW. The process is virtually simulated on the AUTOMATION STUDIO software (version 6.2). The intelligent control strategy used in the present work is based on fuzzy logic that uses human intelligence for a particular desired outcome. The effectiveness of the recommended controller is contrasted with that of a conventional PID controller in the following paper.
Shock wave Boundary Layer Interaction (SWBLI) in hypersonic flow over a Blunt body double wedge configuration
Authors: Meshram S , Siva Vayala , Peetala R K
Published: August 2019

Present investigations are focused on the study of effects of dimensional and parametric changes in shock wave boundary layer interaction (SWBLI) for an axisymmetric double wedge with leading edge bluntness in hypersonic flows. This study is specifically the point of interest since it attributes most of the characteristics of the hypersonic flow around the atmosphere re-entry vehicles. Successfully implemented simulations in hypersonic flow are in a double wedge configuration, to study shock wave boundary layer interaction in hypersonic flows. Inversion radius was found at different deflection angles for change in leading edge radius (LER). It was found that for lower deflection angle Crocco’s theorem affect the flow early compared to higher deflection angles. Shock-shock Interaction-I (SSI I) and Shock-shock Interaction-II (SSI II) shifts downstream with increase in leading edge radius. (Key Words: Hypersonic flows, Shock wave boundary layer interaction, Shock–shock interaction and Leading edge radius)
CFD Analysis of flow around fish
Authors: Palit Swastika , Sinha Shreya , Aylmer Britto R , Arockia Selvakumar A
Published: August 2019

The study of fish like bodies in the liquid is a challenging research area in the fields of bio-locomotion and biomimetics. The power and maneuvering of swimming fish will help a lot in the field of underwater vehicles. Mainly the effect of tail oscillation and abdomen oscillation on fluid flow around such a body is highly unsteady, generating vortices and requiring detailed analysis of fluid-structure interactions. In the present context, a computational fluid dynamic (CFD) simulation of a tilapia fish has been developed to study about the fluid flows around this body when moving in water using the k-epsilon turbulence model. A parametric analysis of the variables that affect the flow surrounding the body is presented, along with flow visualizations. In the present study, a detailed unsteady and transient CFD analysis of the effect of tail and abdomen oscillation on the fluid flow around the fish has been studied. The simulation produces a motion of the tail and abdomen in the (x, y) plane, with both the tail and abdomen oscillating in the form of a sinusoidal wave. Detailed CFD analysis is done and results in terms of the aerodynamic force coefficients namely the lift and drag coefficients, pressure contour and velocity contour have been presented and discussed for the linear motion of fish along z-axis along with periodic oscillations of tail and abdomen in the (x,y) plane. It was observed that both the aerodynamic coefficients and forces came out to be very less which paves way for the motion of the fish with high efficiency. The analysis provided by the simulations has allowed the flow surrounding the tilapia fish undergoing periodic oscillations along with a linear motion to be studied in detail.
Numerical analysis of drag and lift coefficient of a Sport Utility Vehicle (SUV)
Authors: Samy G S , Thirumalai Kumaran S , Uthayakumar M , Sivasubramanian M , Bhagavathi Sankar Krishna
Published: August 2019

The paper describes the modeling and analysis of a Sport Utility Vehicle (SUV). The present study mainly focuses on the reduction of aerodynamics drag and lift coefficient of a car, which helps to improve the vehicle performance and fuel efficiency. Usually the aerodynamic drag and lift is insignificant at low vehicle speed but the magnitude of air resistance becomes considerable with accelerating the vehicle. The Computational Fluid Dynamics (CFD) helps to analyze the flow stream around a SUV. The modeling software is used to design a 3D car model and the flow stream is analyzed by ANSYS Fluent. Initially, the first model was analyzed at various velocity conditions using Reynolds-Averaged Navier–Stokes (RANS) with standard k-ε model. The basic model of SUV has a drag coefficient and lift coefficient value of 0.62 and 0.099 respectively. Initially the first model is designed by introducing air splitter on roof and based on the results the second model is designed by introducing 15 degree boat tailing angle with first model. The drag reduction is reduced by 6.45% for first model and 19.35% for second model compared to the base model. Similarly, the lift coefficient is reduced by 2.02% for first model and 30.30% for the second model. Moreover the second model produces low drag and lift coefficient than first and base model. A significant reduction is observed in first model when compared to the base model. The vector plots are used to examine the streamline path of both the models.
Performance evaluation of a bulb turbine designed for ultra-low head applications
Authors: Shandilya Sonal , Shelar Sujit P. , Prasad Das Shyama , Chatterjee Dhiman , Saini R. P.
Published: August 2019

Hydropower is one of the most common forms of clean source of electricity and forms an important source of power for a country like India. This paper is aimed to design mini-hydropower which utilizes ultra-low head and can be used for decentralized power generation and utilization for remote villages. In order to achieve this purpose an axial flow turbine without any guide vanes is designed. This design process is adopted because the presence of inlet guide vanes in the conventional bulb turbines may pose maintenance problem of clogging and also the design is not fish friendly. Another aspect of micro- or mini-hydropower is the non-availability of large reservoirs and there is likelihood that these turbines may be installed as a run-of-the-river type with some seasonal variation of flow rate. The turbine efficiency should be as much as insensitive to the variation in flow rate as possible. In our work, the turbine is expected to produce a relatively flat efficiency flow rate-curve over a range of flow rates. The peak efficiency obtained is about 74%. There is a need to improve the peak efficiency and hence loss analysis is carried out. It was found that the swirling flow in the draft tube downstream of the turbine contributes to a monotonic increase in loss with an increase in flow rate.
Solidification in Stratified Flow of Two Immiscible Fluids in a Double-Bend
Authors: Hongying Li , Goharzadeh Afshin , Jing Lou , Yit Fatt Yap
Published: August 2019

This article presents an investigation of solidification in stratified flow of two immiscible fluids in a double-bend. A combined enthalpy-level-set approach for solidification is employed. The fluid-solid and fluid-fluid interfaces are captured respectively using the enthalpy and the level-set methods. The approach is verified against the scenario of a thick water layer sandwiched between a wall and an oil layer with water solidifies on the wall where semi-analytical solution exists. With the approach verified established, the effects of Reynolds number, Stefan number, viscosity ratio, thermal diffusivity ratios on flow and heat transfer are investigated.
Study of Interference Effects on Chimneys
Authors: Shruti K , Rajesh Sreeram , Sabareesh GR , Rao PN
Published: August 2019

Fluid flow studies play a vital role in proper assessing of wind loadson buildings and other civil engineering structures with various shapes. The presence of adjacent structure may alter wind loads on the structure of interest, by altering the fluid dynamics surrounding the structure. This effect is termed as interference effect and it depends on various factors such as terrain category, wind angle, geometry & orientation of the structure, spacing between the structures etc. Thus, proper assessment of interference effect with above factors, can lead to efficient design of structures that can withstand the load variations due to the presence of interfering structures. The existing literature on wind interference effects, focuses more on experimental analysis of the problem, which is both expensive and time consuming. In this regard, computational fluid dynamics (CFD) approach can serve as a quicker and efficient tool. In an attempt to study the effect of geometry &orientation of structures on interference phenomenon, turbulent flows around the buildings, cooling towers and chimneys have been simulated through CFD approach by performing Large Eddy Simulation (LES). In the present study, interference factors of a typical chimney structure has been evaluated by considering the presence of an identical chimney at varying distances, under different wind angles.