Ferroelectricity of pristine Hf_(0.5)Zr_(0.5)O_(2) films fabricated by atomic layer deposition

Hafnium-based ferroelectric films,remaining their ferroelectricity down to nanoscale thickness,present a promising application for low-power logic devices and nonvolatile memories.It has been appealing for researchers to reduce the required temperature to obtain the ferroelectric phase in hafnium-based ferroelectric films for applications such as flexible and wearable electronics.This work demonstrates that a remanent polarization(P_(r))value of>5μC/cm^(2)can be obtained in asdeposited Hf_(0.5)Zr_(0.5)O_(2)(HZO)films that are fabricated by thermal atomic layer deposition(TALD)under low temperature of 250℃.The ferroelectric orthorhombic phase(o-phase)in the as-deposited HZO films is detected by scanning transmission electron microscopy(STEM).This low fabrication temperature further extends the compatibility of ferroelectric HZO films to flexible electronics and avoids the cost imposed by following high-temperature annealing treatments.

中法关于核能与环境的联合研究

本文聚焦核能的环境影响问题,将解决如下核能发电相关的主要环境问题:(1)控制正常运行条件下核设施的放射性排放,评估其非放射性环境影响(取水与非放射性水的排放);(2)乏燃料与放射性废物的长期管理,主要是通过地质处置库处理的乏燃料或放射性废物;(3)防止和缓解严重核事故以及核事故的放射性释放;(4)改善核安全水平,以限制核能的环境影响,提升公众的核能接受度。核能的温室气体排放水平非常低,可以根据需求供应大规模、可调度电力,在此方面核能具有独特的优势。在正常运行工况下,核电站每年释放到周围公众的有效辐射剂量可以忽略不计。国际社会已经开展了大量的努力,以确定可持续管理地质处置条件下高放长寿命放射性废物的方法。过去几次严重核事故中获得的经验为核能生产相关的安全问题提供了经验,也促成了重要的安全改进,其中包括反应堆的设计和运行管理方面的改善以及事故管理指导方针的制定等。事实证明,这些经验是非常宝贵的。严重事故的环境风险已经被大幅降低,相关的规约也已经建立起来,以最大限度地减少严重核事故条件下放射性物质的释放,并避免大规模的人员疏散。还需要继续采取措施,改善反应堆的安全性,提升核工业与核监管机构的透明度,以进一步降低核能的环境影响。

平面问题转轴公式适用性的讨论

平面应力(应变)转轴公式是材料力学应力(应变)分析部分的主要教学内容,尽管转轴公式基于特定的应力(应变)状态导出,但在后续的应用,包括例题与习题中的引用并没有限定于平面应力(应变)状态。为了澄清学生常见疑惑,本文使用简单的方式对该问题进行说明,供教师教学时参考。

函数型正则广义典型相关分析

基于正则广义典型相关分析理论框架,提出一类对于多元函数型数据的充分降维方法。通过积分形式,将平方可积空间中的函数型数据投影至实空间中的一系列数值变量,在整体相关性度量最大的目标准则下,同时确定这些函数型投影方向,实现多元函数型数据向传统数值变量转化的特征信息提取及快速降维过程。在一般基函数系统表示下,推导得到最优投影权重函数的迭代计算方法,该方法对于基函数系统的选取具有独立性。大量仿真结果表明,在有限样本情况下,所提方法能够有效探测多元函数型数据之间的相关关系,且对投影权重函数的估计具有一致性。关于帕金森综合征患者步态的实例数据研究表明,由函数型数据投影得到的数值特征信息具有可解释性,所提方法具有一定实用价值。

Assessment of the Rural Water Supply Potential by Mechanical Wind Pumping Around the Floodplains of Lake Chad

In the present work,an assessment of the rural water supply potential by mechanical wind pumping around the floodplains of Lake Chad has been considered.Inside the floodplains around Lake Chad,available surface water is largely contaminated and represents health hazards to populations.Access to underground and clean water has increasingly become rare.Moreover,clean water scarcity has led to conflict and territorial pressures,which are contributing factors to poverty in the considered area.Four localities,Baga,Baga-Sola,Makari and Nguigmi,respectively,in Nigeria,Chad,Cameroon and Niger have been selected inside the floodplains around Lake Chad,to evaluate the potential of wind power and prospects of windmills development to provide safe drinking-water supply,livestock watering and small-scale irrigation.Long-term satellite-derived data,obtained through the Prediction of Worldwide renewable Energy Resources have been considered suitable and viable alternative to missing site-specific data from ground stations.Windmill of Multi-blade driven piston pump is the preferred water pumping option for this study because of its higher overall system efficiency.The results of this study indicate that mean wind speeds,at 10 m height above ground level,are 4.64 m/s for Baga,4.76 m/s for Baga-Sola,4.32 m/s for Makari and 4.44 m/s for Nguigmi.In addition,wind speeds for Baga,for instance,are in the range of 2.5–10 m(working range of a wind pump),at 10,15,20 and 25 m height agl,for 79.64,82.80,84.79,and 86.19 per cent of the time.Corresponding values for Baga-Sola,Makari and Nguigmi are in the range of 80.50–87.76 per cent,76.86–85,58 per cent,77.92–86.21 per cent,respectively.For a Windmill with a 2 m-blade,a 25 m-height tower and considering a total dynamic head of 30 m,average monthly discharges for the dry season are 1,330,1,374,1,200 and 1,199 m3,respectively for Baga,Baga-Sola,Makari and Nguigmi.Furthermore,corresponding costs of water are 9.53,9.23,10.56 and 10.57 XAF/m3,for Baga,Baga-Sola,Makari and Nguigmi,in that order.

Mathematical Model with Energy and Clustering Energy Based Routing Protocols as Remediation to the Directional Source Aware Routing Protocol in Wireless Sensor Networks

In this paper, a routing protocol for wireless sensor network, baptized energy based protocol (EBP) is proposed. Wireless sensor network presents many challenges and constraints, and one of the major constraints is the routing problem. Due to the limited energy of sensor nodes, routing in this type of network shall perform efficiently to maximize the network lifetime. One of the proposed algorithms is the directional source aware routing protocol (DSAP) which, after simulation, showed a lot of limitations and drawbacks. The modified directional source aware routing protocol (MDSAP) was proposed by the authors of this paper to address some of the DSAP’s limitations but remains limited to a fixed topology, fixed source and stationary nodes. So EBP is proposed and operated under different scenarios and showed, after its simulation using TinyOS, many advantages in terms of load balancing, free looping, minimizing packet error rate and maximizing network lifetime.

Generic Tabu Search

The Multiple Sequence Alignment problem is considered to be an NP-Hard problem, requiring initially a specific encoding schema and design, as for any other of its siblings, to implement and run any of the main categories of heuristic. This paper intends to discuss our proposed generic implementation of the Tabu Search algorithm, a heuristic procedure proposed by Fred Glover to solve discrete combinatorial optimization problems. In this research, we try to coordinate and synchronize different designs/implementations discussed in many literatures, with some of the references mentioned in this paper. The basic idea is to avoid that the search for best solutions stops when a local optimum is found, by maintaining a list of non-acceptable or forbidden (taboo) solutions/costs, called Tabu list or Short-Term Memory (STM). In our algorithm, we attempt to add some executions tracing functionalities in order to help later analysis for initial parameters tuning. On the other hand, we propose to include the concept of a list called Long-Term Memory (LTM), so that some of the best solutions found so far can be saved, for search diversification.

The Architectural Unit Setting up and Architectural Characteristics of Néré, <i>Parkia biglobosa</i>, Jack, R. Br. (Fabaceae)

Parkia biglobosa is a much-loved and over-exploited African savannah species for its socio-economic importance. Knowing and taking into account its architectural unit, which is the basis for diagnosing phenology, productivity and tree health, could provide a new perspective on its sustainable management. The aim of this study is to establish the architectural development in Parkia biglobosa by retrospective analysis. To achieve this objective, 390 individuals of all sizes ranging from seedlings to senescent trees were observed and analysed under various soil and climatic conditions in Côte d’Ivoire. The results showed that Parkia biglobosa is a light plant but shading tolerant. It is a mixed vegetative axis plant, the stem is orthotropic* in its proximal part and plagiotropic* (collapsing) in its distal part in young stage. The tree then transitions to an adult and old stage into a tree with a plagiotropic* axis in the proximal and distal parts, the trunk is built up by superimposing collapsed relay axes that gradually straighten, branching is sympodial*, growth is defined and sexuality is terminal and lateral. The ontogeny takes place in three phases: initiation of development and establishment of the crown (young), then flowering and establishment of the architectural unity (adult) and finally the death of secondary axes in the crown, duplication of the architecture by a series of partial and total reiterations (old). The level of organisation is 5: the phytomere, the module or growth unit, the axis, the architectural unit and the reiterated complex. Retrospective analysis of the modules showed that the dimensions of the growth units are indicators of morphological variation and species adaptation to a changing climate (P < 0.05). However, the equations generated by the morphological and habitat dimension linkage models are not significant (R2 and r < 0.7) to be used as a guide for field data collection. This study represents an initiation into the architectural study of this species and the information provided will serve as a basis for further research into the architecture in relation to the sustainable use of this species.

Data-driven methods for discovery of next-generation electrostrictive materials

All dielectrics exhibit electrostriction,i.e.,display a quadratic strain response to an electric field compared to the linear strain dependence of piezoelectrics.As such,there is significant interest in discovering new electrostrictors with enhanced electrostrictive coefficients,especially as electrostrictors can exhibit effective piezoelectricity when a bias electric field is applied.We present the results of a study combining data mining and first-principles computations that indicate that there exists a group of iodides,bromides,and chlorides that have electrostrictive coefficients exceeding 10 m^(4)C^(–2)which are substantially higher than typical oxide electrostrictive ceramics and polymers.The corresponding effective piezoelectric voltage coefficients are three orders of magnitude larger than lead zirconate titanate.

Strain-induced resonances in the dynamical quadratic magnetoelectric response of multiferroics

For the last few years,the research interest in magnetoelectric(ME)effect,which is the cross-coupling between ferroelectric and magnetic ordering in multiferroic materials,has experienced a significant revival.The extensive recent studies are not only conducted towards the design of sensors,actuators,transducers,and memory devices by taking advantage of the cross-control of polarization(or magnetization)by magnetic(or electric)fields,but also aim to create a clearer picture in understanding the sources of ME responses and the novel effects associated with them.Here we derive analytical models allowing to understand the striking and novel dynamics of ME effects in multiferroics and further confirm it with atomistic simulations.Specifically,the role of strain is revealed to lead to the existence of electroacoustic magnons,a new quasiparticle that mixes acoustic and optical phonons with magnons,which results in resonances and thus a dramatic enhancement of magnetoelectric responses.Moreover,a unique aspect of the dynamical quadratic ME response under a magnetic field with varying frequencies,which is the second harmonic generation(SHG),has not been discussed prior to the present work.These SHGs put emphasis on the fact that nonlinearities should be considered while dealing with such systems.

弹性铁电材料的发展之路

Over the past two decades,flexible electronics have attracted numerous attentions for their potential use as flexible,stretchable,portable and conformable devices in various fields including computing,energy harvesting,robotics,sensors and transductors or health monitoring.

Deep learning for the detection of semantic features in tree X-ray CT scans

According to the industry,the value of wood logs is heavily influenced by their internal structure,particularly the distribution of knots within the trees.Nowadays,CT scanners combined with classical computer vision approach are the most common tool for obtaining reliable and accurate images of the interior structure of trees.Knowing where the tree semantic features,especially knots,contours and centers are within a tree could improve the efficiency of the overall tree industry by minimizing waste and enhancing the quality of wood-log by-products.However,this requires to automatically process the CT-scanner images so as to extract the different elements such as tree centerline,knot localization and log contour,in a robust and efficient manner.In this paper,we propose an effective methodology based on deep learning for performing these different tasks by processing CTscanner images with deep convolutional neural networks.To meet this objective,three end-to-end trainable pipelines are proposed.The first pipeline is focused on centers detection using CNNs architecture with a regression head,the second and the third one address contour estimation and knot detection as a binary segmentation task based on an Encoder-Decoder architecture.The different architectures are tested on several tree species.With these experiments,we demonstrate that our approaches can be used to extract the different elements of trees in a precise manner while preserving good performances of robustness.The main objective was to demonstrate that methods based on deep learning might be used and have a relevant potential for segmentation and regression on CT-scans of tree trunks.

Application of reliability technologies in civil aviation: Lessons learnt and perspectives

We consider reliability engineering in modern civil aviation industry, and the related engineering activities and methods. We consider reliability in a broad sense, referring to other system characteristics that are related to it, like availability, maintainability, safety and durability. We covered the entire lifecycle of the equipment, including reliability requirement identification, reliability analysis and design, verification and validation of reliability requirements(typically involved in the equipment design and development phase), quality assurance(which typically enters in the manufacturing phase), and fault diagnosis and prognosis and maintenance(which are connected to the operation phase). Lessons learnt from reliability engineering practices in civil aviation industry are given, which might serve as reference for reliability managers and engineers, also from other industries with high reliability requirements.

On the origin of the high tensile strength and ductility of additively manufactured 316L stainless steel: Multiscale investigation

We report that 316L austenitic stainless steel fabricated by direct laser deposition(DLD),an additive manufacturing(AM)process,have a higher yield strength than that of conventional 316L while keeping high ductility.More interestingly,no clear anisotropy in tensile properties was observed between the building and the scanning direction of the 3D printed steel.Metallographic examination of the as-built parts shows a heterogeneous solidification cellular microstructure.Transmission electron microscopy observations coupled with Energy Dispersive X-ray Spectrometry(EDS)reveal the presence of chemical micro-segregation correlated with high dislocation density at cell boundaries as well as the in-situ formation of well-dispersed oxides and transition-metal-rich precipitates.The hierarchical heterogeneous microstructure in the AM parts induces excellent strength of the 316L stainless steel while the low staking fault energy of the as-built 316L promotes the occurrence of abundant deformation twinning,in the origin of the high ductility of the AM steel.Without additional post-process treatments,the AM 316L proves that it can be used as a structural material or component for repair in mechanical construction.

Energy based 3D trajectory tracking control of quadrotors with model-free based on-line disturbance compensation

In this work, a Revisited form of the so-called Model-Free Control（R-MFC） is derived.Herein, the MFC principle is employed to deal with the unknown part of a plant only（i.e., unmodeled dynamics, disturbances, etc.） and occurs beside an Interconnection and Damping AssignmentPassivity Based Control（IDA-PBC） strategy. Using the proposed formulation, it is shown that we can significantly improve the performance of the control through the reshaping properties of the IDA-PBC technique. Moreover, the control robustness level is increased via a compensation of the time-varying disturbances and the unmodeled system dynamics. This on-line compensation capability is provided by the MFC principle. The problem is studied in the case of Multi-Input Multi-Output（MIMO） mechanical systems with an explicit application to a small Vertical Take-Off and Landing（VTOL） Unmanned Aerial Vehicle（UAV） where a stability analysis is also provided. Numerical simulations have shown satisfactory results, in comparison with some other control strategies, where an in-depth discussion with respect to the control performance is highlighted by considering several scenarios and using several metrics.

Chaotic light at mid-infrared wavelength

The onset of nonlinear dynamics and chaos is evidenced in a mid-infrared distributed feedback quantum cascade laser both in the temporal and frequency domains.As opposed to the commonly observed route to chaos in semiconductor lasers,which involves undamping of the laser relaxation oscillations,quantum cascade lasers first exhibit regular self-pulsation at the external cavity frequency before entering into a chaotic low-frequency fluctuation regime.The bifurcation sequence,similar to that already observed in class A gas lasers under optical feedback,results from the fast carrier relaxation dynamics occurring in quantum cascade lasers,as confirmed by numerical simulations.Such chaotic behavior can impact various practical applications including spectroscopy,which requires stable single-mode operation.It also allows the development of novel mid-infrared highpower chaotic light sources,thus enabling secure free-space high bit-rate optical communications based on chaos synchronization.

Pole placement approach to coherent passive reservoir engineering for storing quantum information

Reservoir engineering is the term used in quantum control and information technologies to describe manipulating the environment within which an open quantum system operates. Reservoir engineering is essential in applications where storing quantum information is required. From the control theory perspective, a quantum system is capable of storing quantum information if it possesses a so-called decoherence free subsystem （DFS）. This paper explores pole placement techniques to facilitate synthesis of decoherence free subsystems via coherent quantum feedback control. We discuss limitations of the conventional ＇open loop＇ approach and propose a constructive feedback design methodology for decoherence free subsystem engineering. It captures a quite general dynamic coherent feedback structure which allows systems with decoherence free modes to be synthesized from components which do not have such modes.

Strain control of layer-resolved negative capacitance in superlattices

Negative capacitance in BaTiO_(3)/SrTiO_(3) superlattices is investigated by Monte Carlo simulations in an atomistic effective Hamiltonian model,using fluctuation formulas for responses to the local macroscopic field that incorporates depolarizing fields.We show that epitaxial strain can tune the negative capacitance of the BaTiO_(3) ferroelectric layer and the overall capacitance of the system.In addition,we predict and explain an original switching of the negative capacitance from the BaTiO3 layer to the SrTiO_(3) layer at low temperatures for intermediate strains.

Green CoNi_(2)S_(4)/porphyrin decorated carbon-based nanocomposites for genetic materials detection

A one-pot synthesis method was conceptualized and implemented to develop green carbon-based nanocomposites working as biosensors.Porphyrin was synthesized to adorn the surface of nanocomposites making them highly sensitive for giving rise to π-π interactions between the genetic materials,proteins and porphyrin rings.The hydrogen bond formed between the proteins(analytes)and the nitrogen in the porphyrin structure as well as the surface hydroxyl groups was equally probable.In this context,different forms of porphyrins were incorporated to explore the interrelationship between the surface morphology and the ability of detection of genetic material and/or proteins by the aid of the synthesized structures.This phenomenon was conceptualized to optimize the interactions between the biomolecules and the substrate by reaching significant biosensor application in the presence of Anti-cas9 protein and sgRNA(concentration changed between 10 and 500 n mol/L).Almost full quenching of fluorescence emission was observed after addition of 300 n mol/L of Anti-cas9 protein and 250 n mol/L of sgRNA.Surprisingly,CoNi_(2)S_(4)provided 12%-29%cytotoxicity in both HEK-293 and PC12 cell lines.

Editorial

Reconfigurable Intelligent Surface(RIS),also known as intelligent reflecting surface or large intelligent surface,is an emerging new physical-layer technology in the field of wireless communications.The basic idea of RIS is to deploy a reconfigurable passive array in the environment to manipulate the propagation of electron-magnetic waves.RIS promises a new design paradigm for wireless communications,where the wireless propagation environment can be dynamically controlled,which is substantially different from the conventional design that focuses only on the transmitter and receiver.For RIS-aided wireless communications,some of the current methodologies in conventional communication systems need to be revised,and some novel solutions are required to realize the potential benefits of the RIS.Although the number of publications about RIS has recently sharply increased,there are still many challenging issues to be extensively investigated,such as the RIS channel modeling,fundamental performance limits,the system design,joint optimization of the RIS and the transceivers,channel state information acquisition,and interdisciplinary applications.