bluuebunny/crossref_metadata_2025 huggingface dataset:
A NonSmooth Contact Dynamics-based multi-domain solver
Authors: Perales Frederic , Dubois Frederic , Monerie Yann , Piar Bruno , Stainier Laurent
Published: July 2021

This paper presents a micromechanical modeling strategy for complex multibody interactions and the associated numerical framework. The strategy rests on a periodic multibody method in the framework of the NonSmooth Contact Dynamics approach of Moreau (1988) extended to classical domain decomposition problems. Many complex interactions can be taken into account: interactions between discrete elements, between discrete or rigid bodies, (quasistatic) contact or impact, friction or adhesion, decohesion (cracking), etc. The associated numerical platform, Xper, is composed of three independent libraries with Object Oriented Programming. The ability of this computational approach is illustrated by two examples of fracture in heterogeneous materials.
Reduced-order modeling by POD-multiphase approach for fluid-structure interaction
Authors: Liberge Erwan , Pomarede Marie , Hamdouni Aziz
Published: July 2021

This paper describes the Reduced Order Modeling (ROM) for fluid rigid body interaction problem and discusses Proper Orthogonal Decomposition (POD) utilisation. The principal difficulty for using POD being the moving domains, a referenced fixed domain has been introduced. The POD has been applied for the velocity field obtained on the fixed domain. Then a method to reduce dynamical system for rigid body fluid interaction has been developed. This method consists in treating the entire fluid-solid domain as a fluid. The rigid body has then been considered as a fluid, by using a high viscosity which can play the role of a penalisation factor of the rigidity constraint. The fluid flow problem is then formulated on the reference domain and POD modes have been used in the weak formulation.
Fluid-structure interaction in rocket engines
Authors: Lefrançois Emmanuel
Published: July 2021

Numerical approaches to predict side-loads on over-expanded launcher engines, resulting from the aeroelasticity, are proposed in this study: a stability model and a fluidstructure model. The main idea is to offer a better understanding of the repercussions likely to appear from the aeroelastic coupling in terms of side loads resulting from the motion of the compression shock and that may be responsible of damage effects on the current engines. It is notably shown the existence of a given natural torsional frequency of the nozzle for which the measured side loads are maximum, phenomenon associated with a transversal wave in the flow between both walls. These studies aim to improve the only current aeroelastic stability model in over expanded nozzle.
Predicting size effects in nickel-base single crystal superalloys with the Discrete-Continuous Model
Authors: Vattré Aurélien , Devincre Benoit , Roos Arjen , Feyel Frédéric
Published: July 2021

The Discrete-Continuous Model, a coupling between dislocation dynamics and finite elements simulations, is used for modelling size effects in the mechanical properties of single-crystal superalloys. Both formation and evolution of the dislocation microstructures are analysed, and the crucial role of the storage of signed dislocations at the interfaces is discussed. The onset of plasticity is found to scale as the inverse of the channel width, and polarised dislocation networks at the interfaces significantly increase the flow stress with respect to a bulk crystal.
Numerical implementation of a non local criterion to describe the failure of laminates with stress concentrations
Authors: Miot Stéphanie , Hochard Christian , Lahellec Noël
Published: July 2021

A non local ply scale criterion was previously developed for predicting the failure of balanced woven ply structures with stress concentrations. This non local criterion was based on the mean values determined over a Fracture Characteristic Volume (FCV). A behavioural model was developed from a classical Continuum Damage Mechanics (CDM) model. The FCV approach and the CDM behavioural model were implemented in ABAQUS and applied to the case of unbalanced woven ply. Comparisons are made between the experimental data and the modelling predictions obtained on plates with open holes, notches and saw cuts. The numerical implementation of this approach is studied in this paper.
A Lightweight Security Scheme (LSS) for Wireless Node Communication for Border Surveillance System
Authors: Singh Rajeev , Singh Sukhwinder
Published: July 2021

The physical breach across the borders is a very common issue these days among nations sharing boundaries. It is controlled via proper border surveillance system. The border surveillance system is trivially a physical border intrusion detection system in which CCTV cameras are used traditionally to observe manually the presence of some intruder. Instead, we utilize the raspberry PI controller board based wireless sensor nodes fitted with raspberry PI camera for identifying the intruder. Once the intruder is identified, the wireless sensor nodes communicate the messages with the next hop sensor nodes and the message ultimately reaches the control room from where army action may be initiated. In this work, we propose a novel lightweight security scheme (LSS) for raspberry PI based wireless node communication for the Border Surveillance System. We have utilized the XBee (Zigbee) serial communication between raspberry PI based wireless sensor nodes. The proposed scheme is based upon the notion of confusion and correct identification of pattern (byte) in the transmitted messages. The entire communication scheme is lightweight and secure.
Evaluating and Improving a Content Delivery Network (CDN) Workflow using Stochastic Modelling
Authors: Goyal Nupur , Joshi Tanuja , Ram Mangey
Published: July 2021

Content Delivery Networks (CDN) are the backbone of Internet. A lot of research has been done to make CDNs more reliable. Despite that, the world has suffered from CDN inefficiencies quite a few times, not just due to external hacking attempts but due to internal failures as well. In this research work the authors have analyzed the performance of a content delivery network through various reliability measures. Considering a basic CDN workflow they have calculated the reliability and availability of the proposed multi-state system using Markov process and Laplace transformation. Software/Hardware failures in any network component can affect the reliability of the whole system. Therefore, the authors have analyzed the obtained results to find major causes of failures in the system, which when avoided, can lead to a faster and more efficient distribution network.
Mitigation of Malware Proliferation in P2P Networks using Double-Layer Dynamic Trust (DDT) Management Scheme
Authors: Cai Lin , Rojas-Cessa Roberto
Published: July 2021

Peer-to-peer (P2P) networking enables users with similar interests to exchange, contribute, or obtain files. This network model has been proven popular to exchange music, pictures, or software applications. These files are saved, and most likely executed, at the downloading host. At the expense of this mechanism, worms, viruses, and malware find an open front door to the downloading host and gives them a convenient environment for successful proliferation throughout the network. Although virus detection software is currently available, this countermeasure works in a reactive fashion, and in most times, in an isolated manner. In this paper, we consider a trust management scheme to contain the proliferation of viruses in P2P networks. Specifically, we propose a cooperative and distributed trust management scheme based on a two-layer approach to bound the proliferation of viruses. The new scheme is called double-layer dynamic trust (DDT) management scheme. Our results show that the proposed scheme bounds the proliferation of malware. With the proposed scheme, the number of infected hosts and the proliferation rate are limited to small values. In addition, we show that network activity is not discouraged by using the proposed scheme.
E-Health: Chances and Challenges of Distributed, Service oriented Architectures
Authors: Thuemmler Christoph , Fan Lu , Buchanan William , Lo Owen , Ekonomou Elias , Sofyane Khedim Abou
Published: July 2021

Societies are undergoing unprecedented demographic and socio-economical changes on a pace that has never been experienced before. Health care models are in transition to remain affordable for governments and individuals. Mobile technology and cloud computing will play a major role in order to help to achieve the necessary level of virtualization and service aggregation. There are, however, technological challenges in terms of security, trust, user friendliness and deployment of innovative E-Health strategies.
Authenticated Encryption for Low-Power Reconfigurable Wireless Devices
Authors: Khajuria Samant , Andersen Birger
Published: July 2021

With the rapid growth of new wireless communication standards, a solution that is capable of providing a seamless shift between existing wireless protocols and high flexibility as well as capability is crucial. Technology based on reconfigurable devices offers this flexibility. In order to avail this enabling technology, these radios have to propose cryptographic services such as confidentiality, integrity and authentication. Therefore, integration of security services to these low-power devices is very challenging and crucial as they have limited resources and computational capabilities. In this paper, we present a crypto solution for reconfigurable devices. The solution is a single pass Authenticated Encryption (AE) scheme that is designed for protecting both message confidentiality and its authenticity. This makes AE very attractive for low-cost low-power hardware implementation. For test and performance evaluation the design has been implemented in Xilinx Spartan-3 sxc3s700an FPGA. Additionally, this paper analyzes different hardware architectures and explores area/delay tradeoffs in the implementation.
Cooperative Wireless Communications and Physical Layer Security: State-of-the-Art
Authors: Rohokale Vandana Milind , Prasad Neeli Rashmi , Prasad Ramjee
Published: July 2021

One morning, we were waiting for our college bus. The Wipro industry bus was slowly passing nearby us looking for its employees. At the last moment, when the driver increased speed, one person stepped down from the auto rickshaw and shouted “stop the bus, stop the bus”. Voluntarily, whoever was present started shouting “stop, stop the bus”. The sound finally reached the bus driver who stopped the bus, and the employee could catch it in time. This analog from everyday realistic life simply depicts the spirit of cooperative wireless communication which utilizes the information overheard by neighbouring nodes to offer reliable communication between sender and receiver. Future converged wireless networks are expected to provide high data rate services with extension in coverage area. Also, the next generation networks should possess bandwidth efficiency, less power consumption ability with small sized mobile equipment. Multiple-input multiple-output (MIMO) system is the best technique for the provision of communication diversity wherein multiple antennas are installed at the sender and receiver. In today’s miniaturizing electronics era, the hardware implementation of MIMO in the mobile equipment is not feasible due to resource constraints. Cooperative wireless communication (CWC) is the upcoming virtual MIMO technique to combat fading and achieve diversity through user cooperation. Physical layer security (PLS) is the imminent security guarantee for the cooperative communication.
ICT Standards in South Eastern Europe (SEE) Education: Macedonian Case
Authors: Gavrilovska Liljana , Atanasovski Vladimir
Published: July 2021

The Standards Education (SE) in the field of ICT gains increasing momentum worldwide. The strategic value of the ICT standards and their influence on the economy proves essential towards countries’ development and their economic growth. This paper overviews the relevant current SE initiatives with a special emphasis on the South Eastern Europe (SEE) case and Macedonia. It discusses the level of ICT penetration, the recognition of the SE importance and the involvement of the relevant stakeholders in the SE curricula design on various education levels in Macedonia. Finally, the paper pinpoints the future directions towards transparent and harmonized SE.
Global Standardization Education Program Collaborated by Osaka Univ. and MJIIT, UTM
Authors: Nakanishi Hiroshi , Othman Rozhan , Igusa Kunio , Komaki Shozo
Published: July 2021

In Osaka University, the Education on Global Standardization Program (UnivEoGSz) for post-graduate students is offered by the Interdisciplinary Center of Osaka University and extensively developed since 2009. The Malaysia-Japan International Institute of Technology (MJIIT), Universiti Teknologi Malaysia (UTM) is now going to setup the courses of standardization education as a sub program in collaboration with Osaka University for Malaysian academics and university students. In this article, the objectives and frameworks of this global standardization education program will be evaluated, especially on the existing Osaka Univ. program and MJIIT program. The general issues on standardization education and the results of case studies on the current trends of global standardization are discussed. The contents of Osaka Model, which MJIIT is now adopting, are slightly different from the conventional educations regarding the introduction of standards, which was architected for the general local schools and companies. It is expected that the article will give a valuable example for understanding on the future direction of standardization educations and advance further its activities in academic and/or university on the issue. And by promoting this education, we hope the conceptual paradigm regarding standardization will be shifted from the just simple international standardization, as reflecting international expansion of the intellectual property right (IPR) based national standard, to global standardization, as commonly acceptable one beyond IPR.And it focuses more enhancing the innovativeness, entrepreneurial and global standardization activities as well.
End-to-End Service Monitoring for Zero-Touch Networks
Authors: Saraiva de Sousa Nathan F. , Lachos Perez Danny , Esteve Rothenberg Christian , Henrique Gomes Pedro
Published: July 2021

Autonomous management capability is the main pillar for paving Zero-touch Networks and efficiently deliver and operate use cases under the light of 5G requirements. To this end, Closed Control Loop (CCL), Intent-Based Networking (IBN), and Machine Learning (ML) are regarded as enablers to automatically executed all operational processes, ideally without human intervention. In this context, the ETSI Zero-touch network and Service Management (ZSM) framework specifies an end-to-end network and service management reference architecture for managing the full lifecycle of services. However, the whole process of service monitoring is not yet well-consolidated in ETSI ZSM. In this work, we propose the Monitoring Model Generator (MMG) component to automatically construct templates for service monitoring. MMG implements a novel methodology where service deployment models and standard information models are used as inputs to generate a high-level monitoring template, called Service Monitoring Model (SMM) and built upon an ontology-based schema based on the Resource Description Framework (RDF) vocabulary. We present a proof of concept implementation along with an experimental functional validation of the MMG and using RDF data in turtle syntax and format. The resulting monitoring models are then used to define actual monitoring KPIs and construct management policies in a control loop architecture.
Multi-image Reorganization Encryption Based on S-L-F Cascade Chaos and Bit Scrambling
Authors: Song Xiaoming , Xu Daihan , Li Guodong , Xu Wenxia
Published: July 2021

Aiming at the problems of small value range of a single chaotic parameter, low sequence chaos, and transient effects, a composite chaotic system of cascaded Sine-Sine mapping, Logistic chaos and generalized third-order Fibonacci is proposed (S-L-F). The new system is highly sensitive to initial values, the maximum spectral entropy of the generated sequence can reach 0.95, and the value range of the parameter x is expanded to [0,4] compared with the traditional Logistic, indicating that the new system is suitable for generating pseudo-random sequences for image encryption. For the problem that the traditional multi-image encryption scheme can only encrypt images of the same type and size, the practicability is poor, and a multi-image encryption scheme based on image reorganization and biting is proposed. The algorithm recombines any number, different sizes and different types of images into a three-dimensional matrix, converts it into a binary matrix, performs bit-level scrambling and surface cyclic scrambling, and then restores the scrambling matrix to decimal, and the chaotic sequence performs exclusive-or diffusion, and completes simultaneous encryption at one time, which greatly improves the encryption efficiency and scope of application. The NPCR of the ciphertext image is 0.9961, and the UACI is 0.3345, which proves that the ciphertext image can effectively resist the difference attack. The information entropy is greater than 7.999, which can effectively resist attacks. It has certain application value in image information security. Experimental analysis shows that the algorithm has high security and strong practicability.
Une stratégie multi-échelle pour l’étude paramétrique de détails géométriques au sein de structures en contacts multiples
Authors: Boucard Pierre-Alain , Buytet Sandrine , Guidault Pierre-Alain
Published: July 2021

This paper presents a multiscale strategy dedicated to the parametric study of structural details inside a structure with multiple friction contacts. The first point of the method uses a micro-macro approach. It is based on a domain decomposition in substructures and interfaces, which involves the resolution of independent “micro” problems in each substructures and transfers the “macro” information only via the interfaces. In a second point, a multiresolution strategy is used in order to reduce the computational cost in the case of problems with design variables. Moreover, the last one consists in modelling the geometry of details without remeshing. On the one hand, it uses a local enrichissement method, the X-FEM, and, on the other hand, level set functions enable one to easily “activate” the detail.
Numerical simulation of fluid structure interaction, application to vibroacoustic problems
Authors: Alia Ahlem , Charley Jacques
Published: July 2021

In the present work, the transient response of a mechanical system is computed first by using an explicit finite element method. By applying the FFT, it’s transformed into frequency response which allows to use BEM for computing the noise radiated at any point into space. BEM is checked first for an acoustic problem before using it for a vibroacoustic application. The numerical examples show the efficiency of the present method.
Prediction and physical analysis of unsteady flows around a pitching airfoil with the dynamic mesh approah
Authors: Bourdet Sébastien , Braza Marianna , Hoarau Yannick , Akoury Rajah El , Ashraf Arif , Harran Gilles , Chassaing Patrick , Djeridi Henda
Published: July 2021

The fluid structure interaction due to the pitching motion of a NACA0012 aerofoil has been studied numerically at moderate and high Reynolds numbers. The dynamic mesh method has been employed in the code ICARE/IMFT solving the Navier-Stokes equations in compressible flows. At high Reynolds number, the phase-averaged Navier-Stokes equations have been solved, coupled with advanced URANS modelling in the NSMB code. The vortex dynamics and especially the stall are physically captured by the dynamic mesh method and by the URANS/Organised Eddy Simulation approach.
Prise en compte de discontinuités en espace et en temps par la méthode des éléments finis étendus
Authors: Réthoré Julien , Gravouil Anthony , Combescure Alain
Published: July 2021

This paper is aimed at presenting an application of the extended finite element method to the time variable in the framework of dynamic crack propagation. We take advantage of the partition of the unity properties of finite elements and use an enriched basis of shape functions in space as well as time. To solve the problem in time, we use a weak formulation including a continuity condition for the velocity. It allows to model mechanical problems with space and time discontinuities. Applications to dynamic crack growth simulation are presented.
Modèle numérique de clapage
Authors: Farout-Fréson Isabelle , Lefrançois Emmanuel , Dhatt Gouri , Sergent Philippe
Published: July 2021

We are interested here in the mixture composed of incompressible fluid and a certain mass of fluidised solid. The proposed model is based on the averaged form of the hydrodynamic biphasic equations, associated with a sediment transport equation with a specific numerical settling velocity sf w adapted for the dumped dredged material case. Both models (hydrodynamics and transport) are coupled considering the variation of density with a forward scheme. Calibrated on the convective descent on three experimental campaigns in canal of dumping of dredged materials, the model gives a very good agreement of convective descent with almost twenty experiments for materials 100% sand, 100% silt or mixture sand/silt without or with a horizontally ambient current (Villaret et al., 1997; Boutin 1999).
Vers une optimisation de la tenue à la fatigue de pièces forgées intégrant l’histoire mécanique des matériaux
Authors: Bouchard Pierre-Olivier , Caillet Nicolas , Chastel Yvan
Published: July 2021

Forging of metal components induces grain flow orientation, which gives rise to anisotropic mechanical properties. Our study deals with the definition and the use of this grain flow anisotropy into fatigue life calculation. We have focused on high cycle fatigue, and we deal with steels containing malleable inclusions above a critical size. A new multiaxial criterion has been developed on the basis of the Murakami equation. This criterion has been implemented in the finite element code Forge 3®. This computational tool uses a new variable to represent the grain flow orientation provided by forging simulation to account for subsequent fatigue anisotropic behaviour. Moreover, residual stresses resulting from forging are also taken into account to perform the fatigue calculation. Finally, a virtual simulation chain, including Forging and Fatigue calculation is carried out. The final goal is to improve fatigue properties by modifying forging conditions.
Algorithmes hybrides pour l’optimisation globale
Authors: Habbal Abderrahmane , Fourment Lionel , Do Tien Tho
Published: July 2021

We introduce two evolutionnary hybrid optimizers, based on surrogate models which use a limited prescribed number of exact evaluations of the criterion and its gradient. The first algorithm uses a discontinuous ansatz with a clustering technique. The second one uses a Liszka-Orkisz interpolation scheme, and keeps memory of the exactly evaluated individuals of previous generations. These two methods are applied to a 3D forging shape optimization problem. The considered objective combines the total energy cost and a defect criterion. We present numerical results which illustrate the efficiency of the developped algorithms.
Approche inverse améliorée pour la minimisation du retour élastique de pièces embouties
Authors: Elechi Slim Ben- , Naceur Hakim , Knopf-Lenoir Catherine , Batoz Jean-Louis
Published: July 2021

This work is focused on the minimization of the elastic deformed drawn parts after tools removing. We use a Response Surface Method based on Diffuse Approximation and a specific algorithm for the optimum searching. For the deep drawing process simulation, we use the Inverse Approach with stress improvements to take into account the bending and unbending effects. Internal efforts with the final workpiece shape are used for the springback calculation, using an Updated Lagrangian Formulation. Two deep drawing benchmarks are studied to validate the proposed procedure with reference to Abaqus® and Stampack® commercial codes.
Numerical divergent series resummation in fluid flow simulation
Authors: Razafindralandy Dina , Hamdouni Aziz , Allery Cyrille
Published: July 2021

The perturbation theory has proved to be an efficient tool for the numerical resolution of non-linear problems in mechanics. However, it is not suitable for singular problems, for which the series solution is divergent. We propose to use the Borel-Laplace series resummation method for the resolution of such a problem. The resulting algorithm is applied to some model problems in fluid mechanics.
Dynamics and control in precision mechanics
Authors: Preumont André , Marneffe Bruno de , Rodrigues Gonçalo , Nasser Houssein , Deraemaeker Arnaud
Published: July 2021

This paper briefly describes three projects developed at the Active Structures Laboratory of ULB, in connection with precision mechanics. The first one considers the integration of piezoelectric fibers in composite structures for space applications; the second consists of an active piezoelectric bimorph mirror for adaptive optics, and the third considers the vibration isolation of sensitive payloads in spacecraft.
Spider XFEM, an extended finite element variant for partially unknown crack-tip displacement
Authors: Chahine Elie , Laborde Patrick , Renard Yves
Published: July 2021

In this paper, we introduce a new variant of the extended finite element method (Xfem) allowing an optimal convergence rate when the asymptotic displacement is partially unknown at the crack tip. This variant consists in the addition of an adapted discretization of the asymptotic displacement. We give a mathematical result of quasi-optimal a priori error estimate which allows to analyze the potentialities of the method. Some computational tests are provided and a comparison is made with the classical Xfem.
A method for coupling atoms to continuum mechanics for capturing dynamic crack propagation
Authors: Aubertin Pascal , Borst René de , Réthoré Julien
Published: July 2021

Conventionally, dynamic crack propagation is modelled using fracture mechanics (either linear elastic, or with an extension to confined plasticity). Herein, we propose a different view, based on a coupling between an atomic description at the crack tip and a classical continuum description away from it. The paper presents the theoretical background and some first numerical results.
Absorbing interfaces in structural-acoustic coupled problems
Authors: Larbi Walid , Deü Jean-François , Ohayon Roger
Published: July 2021

This work concerns finite element formulations of structural-acoustic interior problems with dissipative interfaces. The main purpose is to establish the link between wall acoustic impedance models and poroelastic appraoches based on the Biot theory. The proposed method consists in determining the acoustic impedance parameters starting from intrinsic characteristics of the porous medium. This impedance is then introduced into the vibroacoustic finite element formulation to take into account the dissipative aspect of the fluid-structure interface.
A fast multipole accelerated BEM for 3-D elastic wave computation
Authors: Chaillat Stéphanie , Bonnet Marc , François Semblat Jean-
Published: July 2021

The solution of the elastodynamic equations using boundary element methods (BEMs) gives rise to fully-populated matrix equations. Earlier investigations on the Helmholtz and Maxwell equations have established that the Fast Multipole (FM) method reduces the complexity of a BEM solution to N log2 N per GMRES iteration. The present article addresses the extension of the FM-BEM strategy to 3D elastodynamics in the frequency domain. Efficiency and accuracy are demonstrated on numerical examples involving up to N = O(106) boundary nodal unknowns.
Two examples of partitioning approaches for multiscale and multiphysics coupled problems
Authors: Dureisseix David
Published: July 2021

Partitioning strategies usually focus on interaction between subsystems. They are good candidates to model couplings at different spatial or time scales. A mechanism for the information transfer between subsystems and / or between scales is therefore required. Herein, we propose examples of a subdomain gluing with different spatial scales, and of a poroelastic coupling featuring different time scales.
Estimation of the strain field from full-field displacement noisy data
Authors: Avril Stéphane , Feissel Pierre , Pierron Fabrice , Villon Pierre
Published: July 2021

In this study, the issue of reconstructing strain fields from corrupted full-field displacement data is addressed. Two approaches are proposed, a global one based on Finite Element Approximation (FEA) and a local one based on Diffuse Approximation (DA). Both approaches are compared on a case study which is supposed difficult (open-hole tensile test). DA provides more stable results, but is more CPU time consuming. Eventually, it is proposed to monitor locally the filtering effect of both approaches, the prospects being an impending improvement of the reconstruction for both approaches.
Simulation of mono-ply and multi-ply woven composite reinforcements forming
Authors: Hamila Nahiene , Hélénon Fabrice , Boisse Philippe , Chatel Sylvain
Published: July 2021

The numerical simulation of composite forming permits to envisage the feasibility of a process without defect but also to know the directions of the reinforcements after shaping. These directions condition strongly the mechanical behaviour of the final textile composite structure. In addition, the angles between warp and weft yarns influence the permeability of the reinforcement and thus the filling of the resin in the case of a liquid moulding process. The forming of composite reinforcement can be made on a single ply or simultaneously on several plies. In this paper the different approaches for the textile reinforcement forming simulation are described. A three node element with arbitrary directions of the yarns with regard to the element sides is presented and used for the simultaneous hemispherical forming of three layers.
Level set based method for design of compliant mechanisms
Authors: Jouve François , Mechkour Houari
Published: July 2021

In the context of structural optimization, we propose two natural extensions of the level set method for the design of compliant mechanisms. Two new objective functions are introduced, well suited to the automatic design of compliant mechanisms, and a strategy for the design of mechanisms adapted to multiple loads is proposed. This work is illustrated with several numericals examples.
Gold-black manufacture, microstructure, and optical characterization
Authors: Munir Nazia B. , Mahan J. R. , Doan Luan C. , Vinh N. Q. , Priestley Kory J.
Published: July 2021

A previous contribution formulates a first-principle dipole antenna theory for predicting the polarization-sensitive directional spectral absorptance of gold-black in the near infrared. The current contribution chronicles a successful effort to validate that theory. After a brief review of gold-black history, we describe in some detail the design and construction of a vapor-deposition cell for laying down gold-black coatings on a mirrorlike gold substrate. The microstructure of 4- and 8-µm-thick coatings is revealed using scanning electron microscopy. An automated bench-level reflectometer has been used to measure the in-plane bidirectional reflectivity of the gold-black coatings in the visible (532 nm) and near-infrared (800 nm) for

p

and

s

polarization. Measurements are reported over incident zenith angles ranging between 10 and 50 deg. Results obtained using the apparatus are consistent with the dipole antenna theory in this range of incident zenith angles.
Effect of lateral diffusion of photoelectrons in the reflection-mode varied-doping AlGaN photocathode on resolution
Authors: Wang Honggang , Zhang Junju , Hou Dianli , Hao Jinguang , Wang Lili , Sai Yaozhang
Published: July 2021

To obtain a high resolution of the reflection-mode AlGaN photocathode by establishing
the modulation transfer function (MTF) model of this photocathode, the
influence of emission layer thickness

T
e

, electron diffusion length

L
d

, recombination velocity at
back-interface

V
b

, and optical absorption coefficient

α

on MTF for varied-doping and
uniform-doping Al0.42Ga0.58N photocathodes have
been given. The computational results suggest that varied-doping
structure has great potentiality in improving both resolution and
quantum efficiency of the reflection-mode
Al0.42Ga0.58N photocathode. This improvement is
mainly attributed to the reduced lateral diffusion of photoelectrons,
which is caused by an electric field generated by the varied-doping
structure, and hence the photoelectron transportation towards
photocathode surface is promoted.
Self-gain-modulation random distributed feedback Raman fiber laser with switchable repetition rate
Authors: Tarasov Nikita , Melnikov Leonid A. , Vatnik Ilya D. , Mazhirina Yulia A. , Churkin Dmitriy V.
Published: July 2021

We experimentally demonstrate a pulsed operation in a random fiber laser operation via self-gain-switching. The pulses have low timing jitter and high average output power. We show that repetition rate switches abruptly while varying the pump power, and introduce a simple formula for oscillation frequencies.
Light-induced micro-vibrator with controllable amplitude and frequency
Authors: Liu Zhihai , Zhang Kai , Jin Wei , Zhang Yu , Zhang Yaxun , Zhang Jianzhong , Yang Jun , Yuan Libo
Published: July 2021

We propose and demonstrate a light-induced micro-vibrator that can perform an adjustable reciprocating vibration based on the Δα-typed photophoretic force. The vibration amplitudes and periods can be precisely controlled and modulated in real-time, and the maximum average restoring speed is as high as 23.26 μm/s. In addition, by using the self-healing properties of the Bessel-like beam, we achieve the simultaneous driving and modulating of three absorbing micro-vibrators. The proposed absorbing micro-vibrator can be used as a novel light-driven micromotor, which is considered to have potential application value in the field of targeted drug delivery, biosensing, and environmental detection.
Compressive parallel single-pixel imaging for efficient 3D shape measurement in the presence of strong interreflections by using a sampling Fourier strategy
Authors: Li Yuxi , Jiang Hongzhi , Zhao Huijie , Li Xudong , Wang Yunfan , Xu Yang
Published: July 2021

We present a compressive parallel single-pixel imaging (cPSI) method, which applies compressive sensing in the context of PSI, to achieve highly efficient light transport coefficients capture and 3D reconstruction in the presence of strong interreflections. A characteristic-based sampling strategy is introduced that has sampling frequencies with high energy and high probability. The characteristic-based sampling strategy is compared with various state-of-the-art sampling strategies, including the square, circular, uniform random, and distance-based sampling strategies. Experimental results demonstrate that the characteristic-based sampling strategy exhibits the best performance, and cPSI can obtain highly accurate 3D shape data in the presence of strong interreflections with high efficiency.
Terahertz transmissive half-wave metasurface with enhanced bandwidth
Authors: You Xiaolong , Ako Rajour T. , Lee Wendy S. L. , Bhaskaran Madhu , Sriram Sharath , Fumeaux Christophe , Withayachumnankul Withawat
Published: July 2021

Polarization conversion is useful for studies of chiral structures in biology and chemistry, and for polarization diversity in communications. It is conventionally realized with wave plates, which, however, present challenges due to limited material availability, as well as narrow bandwidth and low efficiency at terahertz frequencies. To enhance bandwidth and efficiency, the concept of the Huygens' metasurface is adopted here for a transmissive half-wave plate. The half-wave metasurface is designed following the optimal frequency-independent circuit parameters provided by a broadband semi-analytical approach. Simulation results of an optimal design suggest that a 15-dB extinction ratio can be sustained from 219 GHz to 334 GHz, corresponding to a fractional bandwidth of 41.6%. The measured results indicate that the fabricated structure enables a 15-dB extinction ratio from 220 GHz to 303 GHz, with a cross-polarization transmission efficiency above 76.7% for both linear and circular polarizations. This half-wave metasurface design can be readily integrated into compact terahertz systems for diverse applications.
Compact high-contrast silicon optical filter using all-passive and CROW Fano nanobeam resonators
Authors: Cheng Ziwei , Zhang Jiahui , Dong Jianji , Ding Yunhong
Published: July 2021

We propose and experimentally demonstrate a high-order coupled-resonator optical waveguide (CROW) nanobeam filter with semi-symmetrical Fano resonance enhancement. Thanks to the tight arrangement of multiple nanobeams and assistance of the partial transmission element, the designed filter has a high-contrast transmission and low insertion loss. Finally, the fabricated filter has a compact size of

20

µ

m

×

10

µ

m

, a high extinction ratio as much as 70 dB, and an insertion loss as low as 1 dB. This filter shows a passive structure without thermal control configuration for calibration on each resonator. This compact filter can be a basic building block for various applications requiring high extinction ratio filtering, such as single-photon source filtering of integrated photon chips.
Lossy mode resonance fiber-optic sensors based on niobium pentoxide thin film
Authors: Kuznetsov P. I. , Sudas D. P. , Yapaskurt V. O. , Savelyev E. A.
Published: July 2021

In this work, we fabricated and investigated lossy mode resonance (LMR) based fiber-optic refractometers, using a niobium pentoxide coated optical fiber as a sensitive element. In order to do that, thin Nb2O5 films were deposited on the surface of chemically thinned optical fibers by metalorganic chemical vapor deposition (MOCVD). The sensitivities of the first transverse electric (TE) and transverse magnetic (TM) LMRs to the surrounding medium refractive index (SMRI) were measured and compared. Aqueous solutions of glucose and sodium chloride were used as test liquids. The sensor sensitivity to a change in the SMRI enhanced with an increase in the dissolved substance concentration and was greater for glucose solution. The maximum response of the 1-st TE and TM LMRs was 6580 and 6120 nm per refractive index unity (RIU), respectively.
Topological phase transition in an all-optical exciton-polariton lattice
Authors: Pieczarka Maciej , Estrecho Eliezer , Ghosh Sanjib , Wurdack Matthias , Steger Mark , Snoke David W. , West Kenneth , Pfeiffer Loren N. , Liew Timothy C. H. , Truscott Andrew G. , Ostrovskaya Elena A.
Published: July 2021

Topological insulators are a class of electronic materials exhibiting robust edge states immune to perturbations and disorder. This concept has been successfully adapted in photonics, where topologically nontrivial waveguides and topological lasers were developed. However, the exploration of topological properties in a given photonic system is limited to a fabricated sample, without the flexibility to reconfigure the structure in situ. Here, we demonstrate an all-optical realization of the orbital Su–Schrieffer–Heeger model in a microcavity exciton-polariton system, whereby a cavity photon is hybridized with an exciton in a GaAs quantum well. We induce a zigzag potential for exciton polaritons all-optically by shaping the nonresonant laser excitation, and measure directly the eigenspectrum and topological edge states of a polariton lattice in a nonlinear regime of bosonic condensation. Furthermore, taking advantage of the tunability of the optically induced lattice, we modify the intersite tunneling to realize a topological phase transition to a trivial state. Our results open the way to study topological phase transitions on-demand in fully reconfigurable hybrid photonic systems that do not require sophisticated sample engineering.
Combining information from parental and personal experiences: Simple processes generate diverse outcomes
Authors: Stamps Judy A. , Bell Alison M.
Published: July 2021

Experiences of parents and/or offspring are often assumed to affect the development of trait values in offspring because they provide information about the external environment. However, it is currently unclear how information from parental and offspring experiences might jointly affect the information-states that provide the foundation for the offspring phenotypes observed in empirical studies of developmental plasticity in response to environmental cues. We analyze Bayesian models designed to mimic fully-factorial experimental studies of trans and within- generational plasticity (TWP), in which parents, offspring, both or neither are exposed to cues from predators, to determine how different durations of cue exposure for parents and offspring, the devaluation of information from parents or the degradation of information from parents would affect offspring estimates of environmental states related to risk of predation at the end of such experiments. We show that the effects of different cue durations, the devaluation of information from parents, and the degradation of information from parents on offspring estimates are all expected to vary as a function of interactions with two other key components of information-based models of TWP: parental priors and the relative cue reliability in the different treatments. Our results suggest empiricists should expect to observe considerable variation in the patterns observed in experimental studies of TWP based on simple principles of information-updating, without needing to invoke additional assumptions about costs, tradeoffs, development constraints, the fitness consequences of different trait values, or other factors.
Effects of communicating uncertainty descriptions in hazard identification, risk characterization, and risk protection
Authors: Wiedemann Peter , Boerner Franziska U. , Freudenstein Frederik
Published: July 2021

Uncertainty is a crucial issue for any risk assessment. Consequently, it also poses crucial challenges for risk communications. Many guidebooks advise reporting uncertainties in risk assessments, expecting that the audience will appreciate this disclosure. However, the empirical evidence about the effects of uncertainty reporting is sparse and inconclusive. Therefore, based on examples of potential health risks of electromagnetic fields (EMF), three experiments were conducted analysing the effects of communicating uncertainties separately for hazard identification, risk characterisation and risk protection. The setups aimed to explore how reporting and how explaining of uncertainty affects dependent variables such as risk perception, perceived competence of the risk assessors, and trust in risk management. Each of the three experiments used a 2x2 design with a first factor presenting uncertainty descriptions (as used in public controversies on EMF related health effects) or describing a certainty conditions; and a second factor explaining the causes of uncertainties (by pointing at knowledge gaps) or not explaining them. The study results indicate that qualitative uncertainty descriptions regarding hazard identification reduce the confidence in the professional competencies of the assessors. In contrast, a quantitative uncertainty description in risk characterisation–regarding the magnitude of the risk–does not affect any of the dependent variables. Concerning risk protection, trust in exposure limit values is not affected by qualitative uncertainty information. However, the qualitative description of uncertainty regarding the adequacy of protection amplifies fears. Furthermore, explaining this uncertainty results in lower text understandability.
Metabolomic and transcriptomic analysis reveals endogenous substrates and metabolic adaptation in rats lacking Abcg2 and Abcb1a transporters
Authors: Ganguly Samit , Finkelstein David , Shaw Timothy I. , Michalek Ryan D. , Zorn Kimberly M. , Ekins Sean , Yasuda Kazuto , Fukuda Yu , Schuetz John D. , Mukherjee Kamalika , Schuetz Erin G.
Published: July 2021

Abcg2/Bcrp and Abcb1a/Pgp are xenobiotic efflux transporters limiting substrate permeability in the gastrointestinal system and brain, and increasing renal and hepatic drug clearance. The systemic impact of Bcrp and Pgp ablation on metabolic homeostasis of endogenous substrates is incompletely understood. We performed untargeted metabolomics of cerebrospinal fluid (CSF) and plasma, transcriptomics of brain, liver and kidney from male Sprague Dawley rats (WT) and Bcrp/Pgp double knock-out (dKO) rats, and integrated metabolomic/transcriptomic analysis to identify putative substrates and perturbations in canonical metabolic pathways. A predictive Bayesian machine learning model was used to predict in silico those metabolites with greater substrate-like features for either transporters. The CSF and plasma levels of 169 metabolites, nutrients, signaling molecules, antioxidants and lipids were significantly altered in dKO rats, compared to WT rats. These metabolite changes suggested alterations in histidine, branched chain amino acid, purine and pyrimidine metabolism in the dKO rats. Levels of methylated and sulfated metabolites and some primary bile acids were increased in dKO CSF or plasma. Elevated uric acid levels appeared to be a primary driver of changes in purine and pyrimidine biosynthesis. Alterations in Bcrp/Pgp dKO CSF levels of antioxidants, precursors of neurotransmitters, and uric acid suggests the transporters may contribute to the regulation of a healthy central nervous system in rats. Microbiome-generated metabolites were found to be elevated in dKO rat plasma and CSF. The altered dKO metabolome appeared to cause compensatory transcriptional change in urate biosynthesis and response to lipopolysaccharide in brain, oxidation-reduction processes and response to oxidative stress and porphyrin biosynthesis in kidney, and circadian rhythm genes in liver. These findings present insight into endogenous functions of Bcrp and Pgp, the impact that transporter substrates, inhibitors or polymorphisms may have on metabolism, how transporter inhibition could rewire drug sensitivity indirectly through metabolic changes, and identify functional Bcrp biomarkers.