bluuebunny/crossref_metadata_2025 huggingface dataset:
Learning‐based control for discrete‐time constrained nonzero‐sum games
Authors: Mu Chaoxu , Peng Jiangwen , Tang Yufei
Published: March 2021

A generalized policy‐iteration‐based solution to a class of discrete‐time multi‐player non‐zero‐sum games concerning the control constraints was proposed. Based on initial admissible control policies, the iterative value function of each player converges to the optimum approximately, which is structured by the iterative control policies satisfying the Nash equilibrium. Afterwards, the stability analysis is shown to illustrate that the iterative control policies can stabilize the system and minimize the performance index function of each player. Meanwhile, neural networks are implemented to approximate the iterative control policies and value functions with the impact of control constraints. Finally, two numerical simulations of the discrete‐time two‐player non‐zero‐sum games for linear and non‐linear systems are shown to illustrate the effectiveness of the proposed scheme.
Intelligent hybrid automatic repeat request retransmission for multi‐band Wi‐Fi networks
Authors: Wang Zhou , Fang Xuming , Yan Li , He Rong , Long Yan
Published: March 2021

With the increase of Wi‐Fi connections and throughput, the problems posed by unreliable connection and unstable delay need to be urgently solved through advanced methods. The IEEE 802.11ax standard was designed to improve the reliability of connection and increase the throughput in dense Wi‐Fi scenario where the inter‐site interference becomes more serious and the spectral resources are more insufficient. Furthermore, in the next generation of Wi‐Fi standard IEEE 802.11be, the hybrid automatic repeat request (HARQ) and multi‐band technologies will be introduced to solve the problems of unstable delay, serious interference and insufficient spectrum resources. In this paper, retransmission schemes combined multi‐band and hybrid automatic repeat request are deeply studied to improve the retransmission efficiency. Combining hybrid automatic repeat request with multi‐band, this paper proposes three kinds of retransmission mode: insisting on the current frequency band (ICFB) retransmission, switching to the backup frequency band (SBFB) retransmission and concurrent retransmitting on dual‐band (CRDB). Then, an intelligent selection algorithm of retransmission mode based on machine learning is designed to determine the optimal mode. Theoretical analysis and experimental results show that the proposed method can greatly improve the retransmission efficiency and thereby reduce the transmission latency and increase the throughput for multi‐band Wi‐Fi networks.
Eccentricity fault detection in brushless doubly fed induction machines
Authors: Afshar Mojtaba , Abdi Salman , Oraee Ashknaz , Ebrahimi Mohammad , McMahon Richard
Published: March 2021

A new fault diagnosis method for detecting the rotor eccentricity faults including static, dynamic and mixed eccentricity is proposed for brushless doubly‐fed induction machines (BDFIMs). BDFIMs are attractive alternatives for the conventional doubly‐fed induction generator (DFIG) for offshore wind power generation; therefore, paying attention to their fault detection is essential. Existing fault detection methods for conventional induction machines cannot be directly applied to the BDFIM due to its special rotor structure and stator winding configurations as well as complex magnetic field patterns. This article proposes a novel fault detection method based on motor current signal analysis to determine stator current harmonics, induced by the nested‐loop rotor slot harmonics (NRSHs), as fault indices. The analysis is performed under healthy conditions and with different types of rotor eccentricity. Finally, a sensitivity analysis is carried out to confirm the practicability of the proposed technique with various fault intensities and load conditions. Analytical winding function approach, finite element analysis and experimental tests on a prototype D180 BDFIM are used in this study to validate the proposed fault detection technique.
A hybrid method for recloser and sectionalizer placement in distribution networks considering protection coordination, fault type and equipment malfunction
Authors: Safari Majid , Haghifam Mahmoud‐Reza , Zangiabadi Mansoureh
Published: March 2021

An effective way to improve distribution system reliability is to place switches and protective equipment in the optimal location. Commonly, in the placement problem, the use of equipment in the designated location is assumed to be possible. But in practice, to establish protection coordination between the equipment, it is necessary to remove or relocate some of the equipment. This paper aims to increase distribution companies' profits and reduce customer interruption costs through a feasible solution. A new hybrid method for equipment placement has been proposed that simultaneously solves the protection coordination problem. While determining the optimal number and location of reclosers and sectionalizers, the proposed method ensures protection coordination between equipment (new and existing devices). Furthermore, to achieve a more realistic and accurate model, factors such as equipment malfunction, fault types (transient and permanent), and the relationship between these faults have been carefully considered to formulate the proposed method. In this method, to solve the optimization problems related to equipment placement and protection coordination, genetic algorithm, and linear programming in MATLAB software have been used, respectively. A real‐life distribution network has been utilized to evaluate the proposed method, and the results show the capability and robustness of this method.
CSNet: Cascade stereo matching network using multi‐information cost volume
Authors: Shao XiaoTao , Zhang Wen , Guo MingKun , Guo SiQi , Qian ManYi
Published: March 2021

The disparity map produced by matching a pair of rectified stereo images provides estimated depth information and accurate distance calculations for autonomous driving. For most stereo matching networks, cost volume plays a crucial role in the accuracy of disparity maps. To increase the accuracy of disparity maps, an improved cost volume method called multi‐information cost volume (MICV) is proposed, with the fusion of concatenation volume and improved correlation volume, which is calculated both in inner product space and Euclidean space, to measure the correlation similarity between features in the left and right images. The inclusion of a squeeze and excitation (SE) module further improves MICV by adjusting the contribution of the correlation volume. To refine the disparity map and enhance the semantics of small objects, a cascade stereo network called CSNet is proposed, with a dilation feature fusion unit (DFFU) to calculate and integrate disparity maps from three different scale branches. The smaller scale branches are gradually integrated into the larger scale branches to implement the transmission of semantic information. The proposed method was evaluated using several established benchmarks including the Sceneow, KITTI2012 and KITTI2015 datasets. Experimental results demonstrate that authors' method produces more accurate disparity maps compared with existing state‐of‐the‐art methods.
Tuneable resonance frequency vibrational energy harvester with electret‐embedded variable capacitor
Authors: Ma Xingchen , Yang Xiaoya , von Seggern Heinz , Dai Ying , He Pengfei , Sessler Gerhard M. , Zhang Xiaoqing
Published: March 2021

An electret‐based electrostatic energy harvester featuring tuneable resonance frequency, small size, light weight, and high output power was designed and its performance predicted by the finite element method and verified by experiment. The device consists of a resilient fluorinated polyethylene propylene (FEP) electret film that is metallised on one side with a small seismic mass attached to its centre and an arc‐shaped counter electrode. In principle, such an energy harvester is mechanically a mass‐spring system and electrically a self‐bias voltage variable capacitor and converts vibrational energy into electrical energy by electromechanical coupling. For an energy harvester sample with dimensions of 30 × 10 × 9 mm for which the last dimension denotes the initial depth of the centre of the harvester, the resonance frequency can be tuned from 17 to 70 Hz by stretching the length of the FEP film loaded with a given seismic mass of 0.06 g. For a seismic mass of 0.1 g, the harvester generated a power up to 797 μW to a matching resistor at its resonance frequency of 17 Hz at an acceleration of 1×g, where g is the gravity of the earth. Such energy harvesters are promising candidates for use in self‐powered electronic devices and wireless sensor network nodes.
Lightweight models for detection of denial‐of‐service attack in wireless sensor networks
Authors: Abidoye Ademola P. , Kabaso Boniface
Published: March 2021

Wireless sensor networks (WSNs) are becoming more popular in recent times due to the availability of low cost, the short transmission range of sensor nodes and their easy deployment in different application areas; however, security is crucial for WSNs due to the nature of data they transmit in most cases in their locations. Sensor nodes transmit through an open medium and due to the short communication range of each sensor node, a node may need to transmit through many hops to a final destination. Denial‐of‐service (DoS) is one of the attacks that can be launched against WSNs to prevent legitimate nodes from transmitting/receiving data packets. Developing an attack detection and countermeasure system to mitigate the effect of DoS is not an easy task. This work proposes lightweight models for DoS attack detection in WSNs. We developed different lightweight models and algorithms for the detection and elimination of DoS in WSNs and experimented the same. The performance of data delivery ratio, delay, detection rate, energy consumption, and false‐positive was carried out. The experimental results show that the proposed scheme achieved a high true‐positive detection rate, low false‐positive detection rate, energy‐efficient, and high data reliability. Numerical examples are presented to further validate the effectiveness of the proposed scheme.
Treatment of Sulphate Rich Process Effluents using Coal Fly Ash
Authors: Lekgoba Tumeletso , Ntuli Freeman , Mosweu Bernard
Published: March 2021

Coal fly ash obtained from a local power station was used as an adsorbent in the removal of sulphates in an aqueous solution. The coal fly ash was characterised using an x-ray fluorescence (XRF) which revealed that it was class C and sub-bituminous type fly ash, an x—ray diffractometer (XRD) which revealed the dominance of a large amorphous phase and a Fourier Transform Infrared Spectroscopy (FTIR) which showed the presence of both organic and inorganic functional groups. Adsorbent dosage, contact time, temperature and solution pH were varied and all the parameters showed a higher uptake of sulphate ions with their increase, except pH which showed a decreasing uptake. The pseudo second order model showed a better fit for the sorption data with lower error values than the pseudo first order model. The uptake of sulphate ions followed both the Langmuir and the Freundlich isotherm models with RL values for the Langmuir within the range 0 < RL < 1 and n-values for the Freundlich within the range 0 < n < 10 showing a favourable sorption for both models. All the thermodynamic parameters (ΔG°, ΔH° and ΔS°) were positive indicating a non – spontaneous, endothermic and a random solid – liquid interface. The process was shown to follow a unimolecular layer approach with chemical adsorption as the dominating mechanism. Generally, coal fly ash showed a higher affinity for sulphates leading to its effective removal.
In-situ management of paddy stubble through microbial biodegradation
Authors: Sangwan Vikramaditya , Deswal Surinder
Published: March 2021

After the harvest of crop, the disposal of the rice stubbles remains a notable area of interest in all the growing areas of rice. The present review paper explores and highlights an effective strategy of decomposing the decomposers of the paddy stubble. Due to the increasing production of rice, there is an increase in rice crop residues and stubbles production. Conventional methods of management of paddy involve burning, surface retention, mulching, bailing, incorporation/amalgamation and direct removal. However, there are certain environmental challenges by using available agricultural implements. Thus, this current study demonstrates strategic management of the paddy crop residue for a sustainable environment. The developed eco-friendly methods will render new dimensions for the application of the post harvested residues. The review paper will be significant for sustainable management of the wastes of the paddy crop and hence strategic decomposition method, which will be beneficial for the society, farmers as well as the environment
Using Infoveillance to Identify Community Concerns/Literacy, Reduce Risk, and Improve Response in Pollution and Health Emergencies
Authors: Crampton Andrea L. , Pearce Nargiza , Ragusa Angela T.
Published: March 2021

Contextualised in public health and environmental literacy frameworks, this interdisciplinary research applies the epidemiological concept ‘infoveillance’ to show how major pollution events can be mitigated by better use of information communication technologies (ICTs). Findings from statistical analysis of Google Trends™ data during a major Australian air pollution event (2019–2020 Summer bushfires) are presented to compare community environmental and health concerns, as manifested by Google searches, in three affected states. Internet searches related to air purifiers, air quality, and P2 face masks increased as the measured air quality decreased. The commonality of internet search activity found across states, in response to pollution emergencies, presents a valuable, yet underutilised, information source for disaster management and response by health authorities and businesses. Significant correlations between the public’s keyword searches and pollution risk suggest Google Trends™ are an underutilised ICT for identifying public health literacy, needs, and emergency response. The 2019-2020 bushfire infoveillance analysis suggests earlier intervention/awareness of predictable community response to risk-management may mitigate insufficient supply of personal protective equipment (i.e., air purifiers) and alert authorities of illiteracies requiring immediate, urgent ramification to reduce public health risk and improve emergency response, including for vulnerable populations.
Strategic Ecological Issues: Environmental Problems in a Perspective of Regional Development in Bangka Belitung
Authors: Haryadi Dwi , Ibrahim Ibrahim , Darwance Darwance
Published: March 2021

A region’s development planning should be carried out by referring to the strategic issues faced by the region. Thus, strategic issues become the basis upon which regional governments formulate their policies and work programs. This study examined how each region in Bangka Belitung Islands Province positioned strategic issues of ecology in its regional development planning. The current writers examined eight regional governments’ Regional Medium-Term Development Plan (RMTDP) documents; one of which belongs to the provincial government, while the rest belongs to the regency/city governments. This study found that ecological issues comprised an average 17.6% of the strategic issues in all of the planning documents, the highest of which was found in Belitung Regency’s planning document. In addition, the analysis revealed that the general focus of the strategic ecological issues was environmental damage, which was reported by three of the regions as a result of mining activities. This study provides an illustration of how each regional government is committed to take ecological issues seriously and include them in the strategic issues at the regional level.
Study on Mechanical and Thermal Performance of Building Energy-saving Wall with Insulation Materials
Authors: Chen Fuzhen
Published: March 2021

Sodium alginate and natural fiber were used as modifiers to prepare sodium alginate natural fiber type biological composites. The mechanical properties were characterized by universal testing machine, and the thermal properties were analyzed by conductivity, The effects of wood fiber and straw fiber content on the comprehensive properties of biological composite materials were evaluated by relevant instruments, and the feasibility of biological composite materials as building energy-saving wall insulation materials was evaluated. The results show that the flexural strength, compressive strength and elastic modulus of the composites increase with the increase of wood fiber content. When the wood fiber content is 100%, the mechanical properties of the sample are the best, the flexural strength is 0.573 MPa, and the compressive strength is 1.410 MPa. The results showed that wood fiber and sodium alginate binder were closely combined and had good wettability. The thermal conductivity of biological composite is 0.078-0.089w / (m · K), which means it has good thermal insula tion performance and can be used as thermal insulation material for building energy-saving wall. The results show that the properties of the composite can be improved by adding a higher proportion of wood fiber and a certain amount of glyoxal crosslinking agent.
Analysis on Electric Vehicles Solving Carbon Emission Problem
Authors: He Shuyang
Published: March 2021

The purpose of this paper is to give a general idea about the future of electric vehicles (EV) and their effects on carbon emission. More specifically, an analysis of the complete transition to EVs by 2050 and whether renewable energy would be enough to supply their electricity demand. Some difficulties are facing such a transition and its background. To support the analysis, an estimation of the supply and demand of electricity in the United States is made using assumptions and data provided by (mostly) government agencies. The estimation uses existing data to predict the amount of renewable power available for EVs in 2050 and the amount of power that EVs will require. These predictions have pointed out that power generated by renewable means (by 2050) available for EVs and the EVs’ power needs are both around 1 trillion kWh. Further discussions about energy storage and transportation conclude that the power generated by renewable energy may not be able to cover all the energy needs of EVs but a significant amount. The complete transition to EV in the future will largely be supported by clean and renewable energy, so the transition is warranted as it will greatly reduce carbon emissions, pollution, and even global warming.
A Case Study: Broadband Over Powerline for Rural Area Deployment in Sarawak
Authors: Nancy B. , Gary Loh C.W , Bazin M. Razi. , Panceras T.M.
Published: March 2021

Broadband over powerline (BPL) is a technology that allows connectivity to internet connection riding via the low tension (LT) power line communication (PLC). A hybrid BPL technology was proposed to the rural area of Sarawak as an alternative option to expand the internet connection without the need to reform a new pathway for internet connectivity. The data signal is transmitted via a communication tower to the access point(s) that is mounted on an electricity pole that provides a low voltage (LV) line. There are three types of custom-designed equipment that has been integrated into the hybrid BPL: the Head End (HE), the Time Division Repeater (TDR) and the Customer Premise Equipment (CPE). Two longhouses at the Bawang Assan, Sarawak settlement has been chosen to initiate the pilot project that required the cooperation of the technology provider, power producer, and the internet service provider. This paper presents a proof of concept (POC) on the deployment, advantages, and limitations for the BPL in a rural setting.
Operational reliability assessment considering independency between wind power ramps and frequency sensitive loads
Authors: Xiao Xiaolong , Gao Qingxu , Han Xiaoqing , Liang Dingkang
Published: March 2021

With the increasing wind power penetration, power system frequency is more vulnerable especially when gust wind periods. Frequency control is used to restore system frequency back to the rated value. But, during frequency control processes, demand of frequency sensitive load (FSL) is different from that of frequency-insensitive load and changes with the change in system frequency. It is necessary to consider load demand combined with dynamic frequency deviation. This paper proposed a new reliability evaluation method of generation systems based on blade-element theory and frequency control method. The blade-element theory is utilized to improve the evaluation accuracy of wind power output in the presence of wind power ramp events (WPREs). The frequency control considering dynamic demand of FSL is used to mimic frequency regulation processes and establish reliability evaluation model. Case studies are presented using wind data from a wind farm in Shanxi Providence, and the results suggest that reliability problems caused by FSL can’t be ignored in some cases.
RIT – Radiologie-Informationstechnologen
Authors: Dederichs Maximilian
Published: March 2021

Der MTRA-Beruf ist ein vielfältiger und hochspezialisierter Beruf. Entwicklungen in medizinischen, technischen und informationstechnologischen Bereichen haben einen unmittelbaren Einfluss auf die Tätigkeiten der MTRA.
Update Mammakarzinom 2020 Teil 4 – fortgeschrittenes Mammakarzinom
Authors: Tesch Hans , Müller Volkmar , Wöckel Achim , Ettl Johannes , Belleville Erik , Schütz Florian , Hartkopf Andreas , Thill Marc , Huober Jens , Fasching Peter A. , Kolberg Hans-Christian , Schulmeyer Carla E. , Welslau Manfred , Overkamp Friedrich , Fehm Tanja N. , Lux Michael P. , Schneeweiss Andreas , Lüftner Diana , Janni Wolfgang
Published: March 2021

Nachdem in den letzten Jahren bei der Behandlung von Patientinnen mit fortgeschrittenem Mammakarzinom zunehmend Substanzen mit einer guten Effektivität zum Einsatz kommen, die spezifische Signalwege angreifen, sind nun neue Therapien und Ansätze hinzugekommen, die sich tatsächlich auf ganz spezifische Veränderungen beziehen wie die Behandlung von Patientinnen mit HR+/HER2−-Tumoren mit einer PIK3CA-Mutation. Ebenso ist die Behandlung von Patientinnen mit einer BRCA1- oder BRCA2-Mutation durch die Einführung der PARP-Inhibitoren verbessert worden. Nun wird zunehmend versucht, Therapieindikationen aufgrund molekularer Muster auszudehnen und weitere Patientinnen zu identifizieren, die von einer Therapie profitieren könnten, und die neu etablierten Therapiemethoden in bestehende Therapiesequenzen einzubinden. Diese Übersichtsarbeit fasst die neuesten Erkenntnisse in diesem Zusammenhang zusammen.
Head Impact Situations in Professional Football (Soccer)
Authors: Beaudouin Florian , Demmerle Daniel , Fuhr Christoph , Tröß Tobias , Meyer Tim
Published: March 2021

To assess head impact incidents (HIIs) and to distinguish diagnosed head injuries from other incidents, a video observation analysis of match HIIs was conducted in the German Bundesliga (2017/18 season). Video recordings of each match were screened to identify the respective events. Head injury data were identified by a prospective injury registry. HII and head injury incidence rates (IR) were calculated with 95% CIs. The total number of HIIs was 1,362 corresponding to an IR of 134.9/1000 match hours (95% CI 127.9–142.2). In 123 HII (IR 12.2, 95% CI 10.2–14.5) the contact was classified as severe. Head contact with the opponent was the most frequent cause (85%). The most frequent mechanism was in 44% (combined) the arm and elbow-to-head, followed by head-to-head and hand-to-head contacts (each 13%). In 58%, the HIIs occurred during header duels. Twenty-nine head injuries were recorded (IR 2.9, 95% CI 2.0–4.1). Concussions/traumatic brain injuries accounted for 48%, head/facial fractures 24%, head/facial contusions 21%, and lacerations/abrasions 7%. The number of HIIs not classified as concussions/more severe trauma was high. Identification of HIIs and head injury severity should be improved during on-field assessment as many head injuries might go unrecognised based on the large number of HIIs.
Reha-Kliniken: Die Angst vor dem Frühjahr
Authors: Doelfs Guntram
Published: March 2021

Seit Wochen werden die Warnungen über eine sich zuspitzende wirtschaftliche Notlage vieler Reha-Kliniken immer lauter. Trotz vorhandener Corona-Hilfsprogramme würden viele Einrichtungen das Frühjahr finanziell nicht überleben, prophezeien unisono mehrere Branchenverbände. Sie fordern vom Gesetzgeber bessere und präziser gefasste Zuschlagsregelungen.
Bergman Clinics: Ein neuer Player betritt den Krankenhausmarkt
Authors: Krämer Nicolas
Published: March 2021

Der Klinikverbund Bergman Clinics aus den Niederlanden ist jetzt auch in Deutschland aktiv. Der private Träger bringt frischen Wind in das hiesige Gesundheitswesen. Seine Wachstumsstrategie verfolgt Ansätze, von denen andere Klinikbetreiber lernen könnten.
Streit um Approbation: Und es geht weiter
Authors: Heeser Alexandra
Published: March 2021

In der kma-Ausgabe April 2020 haben wir berichtet, wie deutsche Bürokratie den Ärztemangel verschärft. Was ist aus den Ärzten geworden, die 2020 in Polen ihr Examen gemacht haben? Wird ihre Approbation nach einem Jahr nun hierzulande endlich anerkannt? Und wie sieht die Regelung für die kommenden Medizinstudenten aus? kma geht diesen Fragen nach.
Advanced techniques for quantum-state specific reaction dynamics of
gas phase metal atoms
Authors: Xu Ang , Ma Yu-jie , Yan Dong , Li Fang-fang , Liu Jia-xing , Wang Feng-yan
Published: March 2021

One of the themes of modern molecular reaction dynamics is to characterize elementary chemical reactions from “quantum state to quantum state”, and the study of molecular reaction dynamics in excited states can help test the validity of modern chemical theories and provide methods to control chemical reactions. The subject of this review is to describe the recent experimental techniques used to study the reaction dynamics of metal atoms in the gas phase. Through these techniques, information such as the internal energy distribution and angular distribution of the nascent products or the three-dimensional stereodynamic reactivity can be obtained. In addition, by preparing metal atoms with specific excited electronic states or orbital arrangements, information about the reactivity of the electronic states enriches the relevant understanding of the electron transfer mechanism in metal reaction dynamics.
Micro-mechanical assembly and characterization of high-quality Fabry–Pérot microcavities for the integration of two-dimensional materials
Authors: Rupprecht Christoph , Lundt Nils , Wurdack Matthias , Stepanov Petr , Estrecho Eliezer , Richard Maxime , Ostrovskaya Elena A. , Höfling Sven , Schneider Christian
Published: March 2021

Integrating monolayers of two-dimensional semiconductors into optical microcavities is challenging because of the very few available approaches to coat the monolayers with dielectric materials without damaging them. Some strategies have been developed, but they either rely on complicated experimental settings and expensive technologies or limit the achievable cavity quality factors. Thus, high quality Fabry–Pérot microcavities are not widely available to the community focusing on light-matter coupling in atomically thin materials. Here, we detail a recently developed technique to micro-mechanically assemble Fabry–Pérot microcavities. Our approach promotes strong coupling conditions with excitons in atomically thin materials, it does not rely on difficult or expensive technologies, it is reproducible, and it yields microcavities with quality factors approaching 4000. It is ideally suitable for engineering coupled monolayer-cavity systems of advanced complexity in small-scale laboratories.
Self-referencing circular dichroism ion yield measurements for improved statistics using femtosecond laser pulses
Authors: Ring T. , Witte C. , Vasudevan S. , Das S. , Ranecky S. T. , Lee H. , Ladda N. , Senftleben A. , Braun H. , Baumert T.
Published: March 2021

The combination of circular dichroism with laser mass spectrometry via the measurement of ion yields is a powerful tool in chiral recognition, but the measured anisotropies are generally weak. The method presented in this contribution reduces the measurement error significantly. A common path optical setup generates a pair of counter-rotating laser foci in the interaction region of a time-of-flight spectrometer. As the space focus condition is fulfilled for both foci individually, this becomes a twin-peak ion source with well separated and sufficiently resolved mass peaks. The individual control of polarization allows for in situ correction of experimental fluctuations measuring circular dichroism. Our robust optical setup produces reliable and reproducible results and is applicable for dispersion sensitive femtosecond laser pulses. In this contribution, we use 3-methyl-cyclopentanone as a prototype molecule to illustrate the evaluation procedure and the measurement principle.
Optimal design of a driver of interdigital transducers used to generate standing surface acoustic waves for cell sorting
Authors: Pei Zhiguo , Ma Yuting , Wang Ce , Wu Yunliang , Song Feifei , Wu Xiaodong
Published: March 2021

A compact driver based on current feedback amplifiers is designed to drive interdigital transducers (IDTs) that generate standing surface acoustic waves for cell sorting. Compared with commercial RF amplifiers, this driver can be used to drive a wider range of loads without impedance matching. Furthermore, the driver works in a switch mode triggered by target cells, which significantly reduces power consumption in the system. A Butterworth–Van Dyke equivalent circuit was fabricated to study the electrical characteristics of the IDTs, and the driver was designed and optimized by circuit simulations. A cell sorter was constructed and tested experimentally to demonstrate that the driver meets sorting requirements. The driver allows the cell sorter to extract rare cells while otherwise consuming low power.
Next generation ferroelectric materials for semiconductor process integration and their applications
Authors: Mikolajick T. , Slesazeck S. , Mulaosmanovic H. , Park M. H. , Fichtner S. , Lomenzo P. D. , Hoffmann M. , Schroeder U.
Published: March 2021

Ferroelectrics are a class of materials that possess a variety of interactions between electrical, mechanical, and thermal properties that have enabled a wealth of functionalities. To realize integrated systems, the integration of these functionalities into semiconductor processes is necessary. To this end, the complexity of well-known ferroelectric materials, e.g., the perovskite class, causes severe issues that limit its applications in integrated systems. The discovery of ferroelectricity in hafnium oxide-based materials brought a renewed interest into this field during the last decade. Very recently, ferroelectricity was also verified in aluminum scandium nitride extending the potential of seeing a wealth of ferroelectric functions in integrated electronics in the future. This paper discusses the prospects of both material systems in various applications.
Diffusion regime of electron–electron collisions in weakly ionized plasmas
Authors: Breizman B. , Stupakov G. , Vekstein G.
Published: March 2021

We consider weakly ionized plasma where frequent elastic scattering of electrons on neutrals changes the individual acts and the rate of electron–electron collisions significantly. In this case, the kinetics of electron thermalization is very different from that in fully ionized plasma. The colliding electrons do not move freely. They, instead, diffuse because of fast scattering on neutrals. We demonstrate how a proper account of this diffusion enables one to estimate the characteristic time of electron thermalization. We also present a rigorous derivation of the kinetic equation for electrons by using Bogolyubov's method based on Liouville equations for multi-particle distribution functions.
Permittivity acquisition of plasmonic materials at epsilon near zero wavelengths
Authors: Zheng Jun , Almossalami Hossam A. , Chen Kuanan , Yu Xinlan , Ye Hui
Published: March 2021

Due to their unique optical properties, plasmonic materials are widely used in nonlinear optics, nanophotonics, optoelectronics, photocatalysis, biosensing, information storage, etc. Researchers usually need to know the detailed permittivity behavior at the vicinity of surface plasmons’ excitation wavelengths, which in turn are located near the zero points of the real part of the permittivity called epsilon-near-zero (ENZ). We hereby introduce a spectral fitting method to quickly obtain the materials' permittivity at the ENZ region and summarize the experiences of selecting dispersion models and optimizing model parameters. Specifically, we have made a detailed description of the optical constant fitting process for a series of plasmonic materials such as heavily doped semiconductors, transparent conductive oxides, organic conductive materials, two-dimensional materials, and sandwiched composites. Hopefully, to provide specific data and theoretical support for researchers in the field of photoelectric properties of plasmonic materials.
Detection of photon statistics and multimode field correlations by Raman processes
Authors: Schlawin Frank , Dorfman Konstantin E. , Mukamel Shaul
Published: March 2021

Glauber’s g(2)-function provides a common measure of quantum field statistics through two-photon coincidence counting in Hanbury Brown–Twiss measurements. Here, we propose to use nonlinear optical signals as a tool for the characterization of quantum light. In particular, we show that Raman measurements provide an alternative direct probe for a different component of the four-point correlation function underlying the g(2)-function. We illustrate this capacity for a specific quantum state obtained from a frequency conversion process. Our work points out how the analysis of controlled optical nonlinear processes can provide an alternative window toward the analysis of quantum light sources.
Large elastocaloric effect in a Heusler-type Co50V35Ga14Ni1 polycrystalline alloy
Authors: Liu Cong , Li Dong , Li Zongbin , Yang Bo , Yan Haile , Li Jianrong , Li Zhe , Zhao Xiang , Zuo Liang
Published: March 2021

Solid state refrigeration technology relies on the high-performance materials with remarkable caloric properties. Here, we demonstrate a large elastocaloric effect through stress-induced martensitic transformation in a Heusler-type Co50V35Ga14Ni1 polycrystalline alloy. By rapidly removing a moderate compressive stress of 400 MPa, a large adiabatic temperature change up to −12.1 K is achieved. Moreover, high cyclability of the elastocaloric effect with more than 4000 loading/unloading cycles is also obtained. With the combination of a large elastocaloric effect and good cyclability, Co-V-Ga based alloys hold great potential for environment-friendly solid-state refrigeration applications.
Do link polynomials detect causality in globally hyperbolic spacetimes?
Authors: Allen Samantha , Swenberg Jacob H.
Published: March 2021

Let X be a (2 + 1)-dimensional globally hyperbolic spacetime with a Cauchy surface Σ whose universal cover is homeomorphic to R2. We provide empirical evidence suggesting that the Jones polynomial detects causality in X. We introduce a new invariant of certain tangles related to the Conway polynomial and prove that the Conway polynomial does not detect the connected sum of two Hopf links among relevant three-component links, which suggests that the Conway polynomial does not detect causality in the scenario described.
Multicellular states of viscoelastic thermovibrational convection in a square cavity
Authors: Boaro Alessio , Lappa Marcello
Published: March 2021

The problem of pure thermovibrational flow in a two-dimensional square cavity containing a viscoelastic liquid is investigated in the framework of a numerical approach based on the governing balance equations for mass, momentum, and energy in their complete and non-linear time-dependent form. For problem closure, these equations are complemented with the transport equation for the elastic stress formulated using the finitely extensible nonlinear elastic Chilcott–Rallison (FENE–CR) constitutive model. A complete parametric study is carried out to highlight the different path of evolution taken by the considered viscoelastic fluid with respect to the corresponding Newtonian counterpart when the Gershuni number is increased. Attention is paid to the patterning scenario in terms of time-averaged flow and related multicellular structures. It is shown that the triadic relationship among the typical characteristic time scales involved in these phenomena, namely, the thermally diffusive time, the fluid relaxation time, and the period of vibrations, can lead to a kaleidoscope of states, which differ in regard to the prevailing symmetry and the related spatiotemporal behaviors. Moreover, the complex interaction between the external vibrations and the elastic property of the polymer molecules, mediated by viscous effects, can produce an interesting “intermittent response.”
Aberration characterization of x-ray optics using multi-modal ptychography and a partially coherent source
Authors: Moxham Thomas E. J. , Laundy David , Dhamgaye Vishal , Fox Oliver J. L. , Sawhney Kawal , Korsunsky Alexander M.
Published: March 2021

Ptychography is a scanning coherent diffraction imaging technique that provides high-resolution imaging and complete spatial information of the complex probe and object transmission function. The wavefront error caused by aberrated optics has previously been recovered using ptychography when a highly coherent source is used, but has not been demonstrated with partial coherence due to the multi-modal probe required. Here, we demonstrate that partial coherence can be accounted for in ptychographic reconstructions using the multi-modal approach and assuming that decoherence arises from either the probe or the object. This equivalence recovers coherent (or single state) reconstructions of both the probe and the object even in the presence of partial coherence. We demonstrate this experimentally by using hard x-ray ptychography with a partially coherent source to image a Siemens star test object and to also recover the wavefront error from an aberrated beryllium compound refractive lens. The source properties and resolving capabilities are analyzed, and the wavefront error results are compared with another at-wavelength metrology technique. Our work demonstrates the capability of ptychography to provide high-resolution imaging and optics characterization even in the presence of partial coherence.
Underwater stealth metasurfaces composed of split-orifice–conduit hybrid resonators
Authors: Lee Dongwoo , Jang Yeongtae , Park Jeonghoon , Kang In Seok , Li Jensen , Rho Junsuk
Published: March 2021

The development of sound-absorbing materials for noise reduction in daily life has been a prolonged issue that also applies to a recognized need for submarine anechoic tiles to stay independent from SONAR (SOund NAvigation Ranging). Here, we present an underwater stealth metasurface that uses split-orifice–conduit (SOC) hybrid resonators to significantly reduce its acoustic reflectance. A theoretical analysis of SOC elements provides an approach to quantifying acoustic characteristics using the transfer matrix method in a single metasurface. The findings confirm that we can tune the absorption with respect to a resonating frequency by adjusting geometrical parameters. Utilizing a hybrid mechanism that enables easy access to coupled resonances, we obtain broadband absorption spectra even in the presence of a covariant sound speed profile in the deep sea and a thermoviscous effect on unit cells of the metasurface. Such a metasurface will provide a further step toward developing feasible underwater stealth technologies for submarines and remains to be experimentally demonstrated.
Effect of atom substitutions on the magnetic properties in Ce2Fe17: Toward permanent magnet applications
Authors: Yin Li , Parker David S.
Published: March 2021

Due to the rapidly developing technologies and huge market demand, there has been increasing interest internationally in exploring permanent magnet formulations in addition to the well-known Nd2Fe14B and SmCo5/Sm2Co17. Given Fe's low materials cost and generally high magnetization, Fe-rich rare earth binaries such as Ce2Fe17 comprise a rich “hunting ground” for such new materials. While this compound suffers from a low ordering point and is a helimagnet, these difficulties are easily remedied by the substitution of appropriate amounts of cobalt for Fe, with room-temperature saturation magnetization as high as 1.5 T. Here, we try to switch the all-important magnetic anisotropy from planar to uniaxial behavior in Ce2Fe17 via 18h- and 6c-type atom substitutions with Si, Ir, and numerous other atoms. The uniaxial magnetocrystalline anisotropy is successfully achieved in the 6c-site-substituted Ce2Fe15Ir2 systems, along with large magnetization. We find that iridium substitution, in particular, induces a substantial uniaxial anisotropy of 11.25 MJ/m3, which is comparable to most of the current rare earth permanent magnets. Although the iridium substitution is costly, the finding of Ir-triggered uniaxial magnetic anisotropy indicates the potential of Ce–Fe-based alloys for permanent magnets.
C-shaped chiral waveguide for spin-dependent unidirectional propagation
Authors: Kandil Sara M. , Sievenpiper Daniel F.
Published: March 2021

Spin-dependent unidirectional propagation is one of the most intriguing features of the Quantum spin-Hall effect, which was studied intensively in electronic systems and led to the discovery of topological insulators. Recently, it was proven that evanescent waves intrinsically possess transverse spin that is dependent on the direction of propagation. This has enabled new applications in unidirectional waveguiding and integrated quantum optics. In this work, we study via numerical simulations a waveguide design consisting of C-shaped metallic particles characterized by extrinsic chirality and strong transverse spin. The design supports confined, spin-dependent unidirectional propagation with a high directionality ratio reaching 95%. We also study the effect of placing different local defects on the directionality of the supported guided mode.
Electrical circuits involving fractal time
Authors: Khalili Golmankhaneh Alireza , Kamal Ali Karmina , Yilmazer Resat , Welch Kerri
Published: March 2021

In this paper, we develop fractal calculus by defining improper fractal integrals and their convergence and divergence conditions with related tests and by providing examples. Using fractal calculus that provides a new mathematical model, we investigate the effect of fractal time on the evolution of the physical system, for example, electrical circuits. In these physical models, we change the dimension of the fractal time; as a result, the order of the fractal derivative changes; therefore, the corresponding solutions also change. We obtain several analytical solutions that are non-differentiable in the sense of ordinary calculus by means of the local fractal Laplace transformation. In addition, we perform a comparative analysis by solving the governing fractal equations in the electrical circuits and using their smooth solutions, and we also show that when α=1, we get the same results as in the standard version.
An investigation of the wakes of stranded cables using particle image velocimetry
Authors: Abdelhady Mohamed , Wood David H.
Published: March 2021

Stranded cables are used in a wide range of applications, but the flow over them has not been studied extensively. Instead, many applications assume circular cylinder behavior when modeling the wake dynamics. This paper provides a detailed study of the wakes of two stranded cables using two-dimensional particle image velocimetry in the streamwise-normal and streamwise-spanwise planes. The first cable had six outer strands and the second had three. A circular cylinder was also investigated experimentally as to provide a benchmark for comparison. The experiments were done in a water channel at a Reynolds number of ∼3100, based on the circumscribing diameter. Proper orthogonal decomposition and phase-averaging were used to investigate the coherent and incoherent fields. The results showed that 3 × 1 with the largest variations in the sectional width experiences a local stream of higher streamwise velocity along the span and that both cables have ∼20% higher mean spanwise velocity, relative to the cylinder. The stranded cable wakes are dominated by alternatively shed Kármán vortices, at a frequency similar to the circular cylinder. However, the Reynolds stresses, the shape factor, and the details of vortex shedding showed substantial alterations associated with the cable strands, including 58% variation, relative to the cylinder, in total, coherent, and incoherent Reynolds stresses for cables along the span. In addition, the cable strands resulted in the elongation and distortion of the mean spanwise vorticity, without changing their magnitude or thickness. Finally, the strands generally increase the magnitudes of turbulent transport and coherent diffusion, and production, especially at the shear layers.
Fast energy release from reactive materials under shock compression
Authors: Matveev Sergey , Dlott Dana D. , Valluri Siva Kumar , Mursalat Mehnaz , Dreizin Edward L.
Published: March 2021

Metal-based reactive nanomaterials (RNMs) can produce two to three times more energy than conventional organic explosives, but the exothermic reactions, which ordinarily require diffusive mixing of separated fuel and oxidizer components, are too slow and do not generate enough gas to produce detonations. Here, we studied shock initiation of 4Al/Bi2O3 and 4Al/BiF3 RNMs produced by arrested reactive milling. Initiated by a 3 km/s impact, which approximates a powerful detonation, fast energy release produced 3200 K temperatures. In the fluoride, a rapid volume increase was also observed. The shock-induced energy release was orders of magnitude faster than when the RNM was heated. Although these RNM powders by themselves likely cannot produce detonations, our results suggest that used as additives in detonating systems, they might significantly boost the energy of chemical explosives.
Microstructure, elastic modulus, and energy storage properties of portion II in the locust semi-lunar process
Authors: Chen Xiaoyong , Hao Zhixiu
Published: March 2021

A locust stores the energy needed for jumping in its semi-lunar processes (SLPs) at the end of the hind leg femur, and portion II of the SLP plays a key role in the energy storage–release process. In this paper, scanning electron microscopy and transmission electron microscopy tests were conducted on portion II to determine its microstructure. The elastic moduli of different directions of portion II were tested by atomic force microscopy. Test data demonstrate that portion II is a layered structure formed by lamination of composite layers with a thickness of 1.09 ± 0.44 µm and chitin layers with a thickness of 0.10 ± 0.02 µm, and the composite layer is a fiber-reinforced structure. The elastic moduli of the composite layers along the fiber direction and perpendicular to the fiber direction are 11.32 ± 1.09 GPa and 10.36 ± 2.64 GPa, respectively. Furthermore, the influence of the change in the thickness of the composite layer, the volume ratio of the composite layer, and the fiber volume content in the composite layer on the maximum von Mises stress and strain energy of portion II was analyzed using the finite element method. The analysis results show that the strain energy corresponding to the actual parameters of portion II is close to the maximum. Under this premise, the maximum von Mises stress is close to the minimum. This suggests that the actual parameters give portion II almost the largest energy storage and then the longest fatigue life.