Electromagnetic responses on microstructures of duplex stainless steels based on 3D cellular and electromagnetic sensor finite element models

Microstructures determine mechanical properties of steels,but in actual steel product process it is difficult to accurately control the microstructure to meet the requirements.General microstructure characterization methods are time consuming and results are not rep-resentative for overall quality level as only a fraction of steel sample was selected to be examined.In this paper,a macro and micro coupled 3D model was developed for nondestructively characterization of steel microstructures.For electromagnetic signals analysis,the relative permeability value computed by the micro cellular model can be used in the macro electromagnetic sensor model.The effects of different microstructure components on the relative permeability of duplex stainless steel(grain size,phase fraction,and phase distribu-tion)were discussed.The output inductance of an electromagnetic sensor was determined by relative permeability values and can be val-idated experimentally.The findings indicate that the inductance value of an electromagnetic sensor at low frequency can distinguish dif-ferent microstructures.This method can be applied to real-time on-line characterize steel microstructures in process of steel rolling.

Progress in weldability research of duplex stainless steels

Duplex stainless steels(DSSs)show better corrosion resistance with higher strength than traditional austenite stainless steels in many aggressive environments,and can be welded properly with almost every welding processes,if proper heat input is provided.Progresses of research works on weldability of DSSs in recent years are reviewed in this paper.Balance control of ferrite/austenite phases is most important for DSSs welding.The phases balance can be controlled with filler materials,nitrogen addition in shielding gas,heat input,post weld heat treatment,and alternating magnetic field.Too high cooling rate results in not only extra ferrite,but also chromium nitride precipitation.While too low cooling rate or heating repeatedly results in precipitation of secondary austenite and intermetallic compounds.In both situations,mechanical properties and corrosion resistance of the DSS joints deteriorate.Recommended upper and lower limits of heat input and maximum interpass temperature should be observed.

A chaotic hierarchical encryption/watermark embedding scheme for multi-medical images based on row-column confusion and closed-loop bi-directional diffusion

Security during remote transmission has been an important concern for researchers in recent years.In this paper,a hierarchical encryption multi-image encryption scheme for people with different security levels is designed,and a multiimage encryption(MIE)algorithm with row and column confusion and closed-loop bi-directional diffusion is adopted in the paper.While ensuring secure communication of medical image information,people with different security levels have different levels of decryption keys,and differentiated visual effects can be obtained by using the strong sensitivity of chaotic keys.The highest security level can obtain decrypted images without watermarks,and at the same time,patient information and copyright attribution can be verified by obtaining watermark images.The experimental results show that the scheme is sufficiently secure as an MIE scheme with visualized differences and the encryption and decryption efficiency is significantly improved compared to other works.

Evaluation of hybrid closed-loop insulin delivery system in type 1 diabetes in real-world clinical practice:One-year observational study

BACKGROUND In 2016,the Food and Drug Administration approved the first hybrid closed-loop(HCL)insulin delivery system for adults with type 1 diabetes(T1D).There is limited information on the impact of using HCL systems on patient-reported outcomes(PROs)in patients with T1D in real-world clinical practice.In this independent study,we evaluated glycemic parameters and PROs over one year of continuous use of Medtronic’s 670G HCL in real-world clinical practice.AIM To assess the effects of hybrid closed loop system on glycemic control and quality of life in adults with T1D.METHODS We evaluated 71 patients with T1D(mean age:45.5±12.1 years;59%females;body weight:83.8±18.7 kg,body mass index:28.7±5.6 kg/m2,A1C:7.6%±0.8%)who were treated with HCL at Joslin Clinic from 2017 to 2019.We measured A1C and percent of glucose time-in-range(%TIR)at baseline and 12 months.We measured percent time in auto mode(%TiAM)for the last two weeks preceding the final visit and assessed PROs through several validated quality-of-life surveys related to general health and diabetes management.RESULTS At 12 mo,A1C decreased by 0.3%±0.1%(P=0.001)and%TIR increased by 8.1%±2.5%(P=0.002).The average%TiAM was only 64.3%±32.8%and was not associated with A1C,%TIR or PROs.PROs,provided at baseline and at the end of the study,showed that the physical functioning submodule of 36Item Short-Form Health Survey increased significantly by 22.9%(P<0.001).Hypoglycemia fear survey/worry scale decreased significantly by 24.9%(P<0.000);Problem Areas In Diabetes reduced significantly by-17.2%(P=0.002).The emotional burden submodules of dietary diversity score reduced significantly by-44.7%(P=0.001).Furthermore,analysis of Clarke questionnaire showed no increase in awareness of hypoglycemic episodes.WHO-5 showed no improvements in subject’s wellbeing among participants after starting the 670G HCL system.Finally,analysis of Pittsburgh Sleep Quality Index showed no difference in sleep quality,sleep latency,or duration of sleep from baseline to 12 mo.CONCLUSION The use of HCL in real-world clinical practice for one year was associated with significant improvements in A1C,%TIR,physical functioning,hypoglycemia fear,emotional distress,and emotional burden related to diabetes management.However,these changes were not associated with time in auto mode.

Developing a duplex ARMS-qPCR method to differentiate genotype Ⅰ and Ⅱ African swine fever viruses based on their B646L genes

Africanswinefever(ASF),causedbythe African swine fever virus (ASFV), is an acute, hemorrhagic, and contagious disease of domestic pigs and wild boars.The disease is notifiable and listed by the World Organization for Animal Health (WOAH)(Wang N et al. 2019).

Joint Flexible Duplexing and Power Allocation with Deep Reinforcement Learning in Cell-Free Massive MIMO System

Network-assisted full duplex(NAFD)cellfree(CF)massive MIMO has drawn increasing attention in 6G evolvement.In this paper,we build an NAFD CF system in which the users and access points(APs)can flexibly select their duplex modes to increase the link spectral efficiency.Then we formulate a joint flexible duplexing and power allocation problem to balance the user fairness and system spectral efficiency.We further transform the problem into a probability optimization to accommodate the shortterm communications.In contrast with the instant performance optimization,the probability optimization belongs to a sequential decision making problem,and thus we reformulate it as a Markov Decision Process(MDP).We utilizes deep reinforcement learning(DRL)algorithm to search the solution from a large state-action space,and propose an asynchronous advantage actor-critic(A3C)-based scheme to reduce the chance of converging to the suboptimal policy.Simulation results demonstrate that the A3C-based scheme is superior to the baseline schemes in term of the complexity,accumulated log spectral efficiency,and stability.

High throughput screening of localised and general corrosion in type 2205 duplex stainless steel at ambient temperature

Bipolar electrochemistry is used to produce a linear potential gradient across a bipolar electrode(BPE),providing direct access to the anodic and cathodic reactions under a wide range of applied potentials.The occurrence of pitting corrosion,crevice corrosion,and general corrosion on type 2205 duplex stainless steel(DSS 2205)BPE has been observed at room temperature.The critical pit depth of 10-20μm with a55%-75% probability of pits developing into stable pits at potential from+0.9 to+1.2 V vs.OCP(open circuit potential)are measured.All pit nucleation sites are either within ferritic grains or at the interface between austenite and ferrite.The critical conditions for pitting and crevice corrosion are discussed with Epit(critical pitting potential)and Ecre(critical crevice potential)decreasing from 0.87 and 0.80 V vs.OCP after150 s of exposure to 0.84 and 0.76 V vs.OCP after 900 s of exposure,respectively.Pit growth kinetics under different applied bipolar potentials and exposure times have been obtained.The ferrite is shown to be more susceptible to general dissolution.

In Band Full Duplex (IBFD) Technology for Next Generation Wireless Networks: A Survey in Cellular Networks

Next-Generation(NextG)wireless communication networks with their widespread applications require high data rates,seamless connectivity and high quality of service(QoS).To cope up with an unprecedented rise of data hungry applications,users demand more spectral resources imposing a limitation on available wireless spectrum.One of the potential solutions to address the spectrum scarce issue is to incorporate in band full duplex(IBFD)or full duplex(FD)paradigm in next generation networks including 5G new radio(NR).Recently,FD has gained the research interest in cellular networks for its potential to double the wireless link capacity and enhancing spectral efficiency(SE).In half duplex(HD)cellular networks,base stations(BSs)can either perform uplink(UL)or downlink(DL)transmission at a particular time instant leading to reduced throughput levels.Due to the advancement in the self interference reduction(SIR)techniques,full duplex base stations(FD-BSs)can be employed to allow simultaneous UL and DL transmissions at the same time–frequency resources as compared to its HD counterpart.It ideally achieves twice the throughput without any additional complexity at user-equipment(UE).This paper covers a detailed survey on FD cellular networks.A series of SIR approaches,UE-UE mitigation techniques are summarized.Various existing MAC protocols and antenna architectures for FD cellular networks are outlined.An overview of security aspects for FD in cellular networks is also presented.Lastly,various open issues and possible research directions are brought up for FD cellular networks.

A compact and closed-loop spin-exchange relaxation-free atomic magnetometer for wearable magnetoencephalography

Atomic magnetometers operated in the spin-exchange relaxation-free(SERF)regime are the promising sensor to replace superconducting quantum interference devices(SQUIDs)in the biomagnetism field.The SERF magnetometer with compact size and good performance is crucial to the new generation of wearable magnetoencephalography(MEG)system.In this paper,we developed a compact and closed-loop SERF magnetometer with the dimensions of 15.0×22.0×30.0 mm^(3)based on a single-beam configuration.The bandwidth of the magnetometer was extended to 675 Hz while the sensitivity was maintained at 22 f T/Hz^(1/2).A nearly 3-fold enhancement of the bandwidth was obtained in comparison with the open-loop control.The implementation of the closed-loop control also greatly improved the dynamic range,enabling the magnetometer to be robust against the disturbance of the ambient field.Moreover,the magnetometer was successfully applied for the detection of humanα-rhythm and auditory evoked fields(AEFs),which demonstrated the potential to be extended to multi-channel MEG measurements for future neuroscience studies.

Subspace Identification for Closed-Loop Systems With Unknown Deterministic Disturbances

This paper presents a subspace identification method for closed-loop systems with unknown deterministic disturbances.To deal with the unknown deterministic disturbances,two strategies are implemented to construct the row space that can be used to approximately represent the unknown deterministic disturbances using the trigonometric functions or Bernstein polynomials depending on whether the disturbance frequencies are known.For closed-loop identification,CCF-N4SID is extended to the case with unknown deterministic disturbances using the oblique projection.In addition,a proper Bernstein polynomial order can be determined using the Akaike information criterion(AIC)or the Bayesian information criterion(BIC).Numerical simulation results demonstrate the effectiveness of the proposed identification method for both periodic and aperiodic deterministic disturbances.

Type Synthesis of Fully Decoupled Three Translational Parallel Mechanism with Closed-Loop Units and High Stifness

In order to solve the problem of weak stifness of the existing fully decoupled parallel mechanism, a new synthesis method of fully decoupled three translational (3T) parallel mechanisms (PMs) with closed-loop units and high stifness is proposed based on screw theory. Firstly, a new criterion for the full decoupled of PMs is presented that the reciprocal product of the transmission wrench screw matrix and the output twist screw matrix of PMs is a diagonal matrix, and all elements on the main diagonal are nonzero constants. The forms of the transmission wrench screws are determined by the criterion. Secondly, the forms of the actuated and unactuated screws can be obtained according to their relationships with the transmission wrench screws. The basic decoupled limbs are generated by combination of the above actuated and unactuated screws. Finally, a closed-loop units construction method is investigated to apply the decoupled mechanisms in a better way on the high stifness occasion. The closed-loop units are constructed in the basic decoupled limbs to generate a high-stifness fully decoupled 3T PM. Kinematic and stifness analyses show that the Jacobian matrix is a diagonal matrix, and the stifness is obviously higher than that of the coupling mechanisms, which verifes the correctness of the proposed synthesis method. The mechanism synthesized by this method has a good application prospect in vehicle durability test platform.

Investigation on influence of alloying on phase transitions of duplex stainless steel based on thermochemical calculation

This paper investigated on influence of different alloying elements added into duplex stainless steel (DSS) on phase transitions using thermochemical methods in comparison with experiment.The results showed that the most possible species in the ferrite phase,austenite phase,σphase,Hcp phase,χphase,and carbide were Cr:Va-type,Fe:Va-type,Ni:Cr:Mo-type,Cr_(2)N-type,Fe_(24)Mo_(10)Cr_(24)-type,and Cr:Mo:C-type,respectively.Furthermore,the Ni,N,Cr,and Mo alloying had significant influences on the transition of each DSS phase.The Ni and N additions obviously raised the temperature at ferrite-1/austenite-1 balance while the Cr and Mo decreased the dual-phase balance temperature.In addition,the Ni addition can promote the precipitating ofσphase at relatively high temperature while the precipitating of Hcp phase at relatively low temperature.The Hcp phase andχphase can be obviously increased by the N addition.The introduction of Cr and Mo notably enhances the precipitation ofσphase.However,the promotion ofχphase precipitation is facilitated by the presence of Mo,while the Cr element acts as an inhibitor forχphase precipitation.Furthermore,the ferrite/austenite ratio tested by experiment was higher than that calculated by thermochemical methods,thus pre-designed solution temperature should be lower about 30-100℃than that calculated by thermochemical methods.

Literature Review of Phase Transformations and Cavitation Erosion of Duplex Stainless Steels

Phase transformation is one of the factors that would significantly influence the ability to resist cavitation erosion of stainless steels. Due to the specific properties of duplex stainless steel, the heat treatment would bring about significant phase transformations. In this paper, we have examined the previous studies on the phase transition of stainless steel, including the literature on the classification of stainless steel, spinodal decomposition, sigma phase transformation, and cavitation erosion of double stainless steel. Through these literature investigations, the destruction of cavitation erosion on duplex stainless steel can be clearly known, and the causes of failure of duplex stainless steel in seawater can be clarified, thus providing a theoretical basis for subsequent scientific research. And the review is about to help assess the possibility of using bulk heat treatment to improve the cavitation erosion (CE) behaviour of the duplex stainless steel 7MoPLUS.

Deformation Mechanism of Bimodal Structured 2205 Duplex Stainless Steel in Two Yield Stages

A kind of micro/nanostructured 2205 duplex stainless steel(DSS)with uniform distribution of nanocrystals was prepared via aluminothermic reaction method.The analysis of stress-strain curve showed that the fracture strength and elongation of the specimen were 946 MPa and 24.7%,respectively.At present,the research on microstructure of bimodal 2205 DSS at room temperature(RT)mainly depended on scanning electron microscope(SEM)observation after loading experiments.The test result indicates that there are two different yield stages in stress-strain curve of specimen during tensile process.The microstructure of duplex bimodal structured stainless steel consists of two pairs of soft hard regions and phases.By studying deformation mechanism of bimodal structured stainless steel,the interaction between soft phase and hard phase are discussed.The principle of composition design and microstructure control of typical duplex stainless steel is obtained,which provides an important research basis for designing of advanced duplex stainless steel.

Closed-Loop System Identification Approach of the Inertial Models

The mathematical model that approximates the dynamics of the industrial process is essential for the efficient synthesis of control algorithms in industrial applications. The model of the process can be obtained according to the identification procedures in the open-loop, or in the closed-loop. In the open-loop, the identification methods are well known and offer good process approximation, which is not valid for the closed-loop identification, when the system provides the feedback output and doesn’t permit it to be identified in the open-loop. This paper offers an approach for experimental identification in the closed-loop, which supposes the approximation of the process with inertial models, with or without time delay and astatism. The coefficients are calculated based on the values of the critical transfer coefficient and period of the underdamped response of the closed-loop system with P controller, when system achieves the limit of stability. Finally, the closed-loop identification was verified by the computer simulation and the obtained results demonstrated, that the identification procedure in the closed-loop offers good results in process of estimation of the model of the process.

热处理对2205双相不锈钢显微组织及性能的影响

采用光学显微镜、显微硬度计和电化学工作站等研究了2205双相不锈钢经不同温度保温不同时间后的显微组织及性能,并分析了其经不同工艺热处理后的γ和α两相比例和析出相的变化。结果表明:2205双相不锈钢初始状态下α和γ相含量分别为41.2%和58.8%。保温时间相同时,随着热处理温度的升高,γ相含量减少,σ相含量先增加后减少,硬度增加,腐蚀电位先降低后增加。保温温度相同时,随着保温时间的延长(0.5~2 h),γ相和σ相含量增加,γ相含量增幅为2.43%~3.87%,σ相含量增幅为0.05%~0.08%,晶粒有长大趋势,硬度逐渐降低,腐蚀电位总体呈降低趋势。当加热温度为950和1000℃时,硬度随保温时间增加而降低的幅度较明显。σ相含量及α/γ比例增加是造成2205双相不锈钢耐腐蚀性能下降的主要原因。

σ相对S32205双相不锈钢力学性能和耐蚀性的影响

通过JMatPro软件模拟计算和试验结合的方式研究了S32205双相不锈钢中σ相的析出行为及对其力学性能和耐蚀性的影响。结果表明:通过JMatPro软件模拟计算得到的S32205双相不锈钢σ相析出鼻尖温度为875℃。当S32205双相不锈钢在875℃保温0~90 min,σ相含量快速增加,当保温时间增加至90~120 min时,σ相含量缓慢上升,而当保温时间为120~240 min时σ相含量达到饱和,最大为6.1%,与模拟计算结果基本符合。随着保温时间逐渐增加,S32205双相不锈钢的屈服强度、抗拉强度及显微硬度先快速增加后逐渐保持稳定,而伸长率呈下降趋势,强度和硬度与σ相体积含量成正比关系,σ相强化机理由Orowan强化机制转变为σ相的高弹性应变能强化机制。不同σ含量的S32205双相不锈钢的电化学试验结果表明随着σ相的含量逐渐增多,基体越容易贫Cr, S32205双相不锈钢越容易产生腐蚀,耐蚀性逐渐降低。

S32101双相不锈钢U形坡口激光填充焊接修复工艺

文中采用开设坡口的方式去除裂纹、通过坡口填充焊接修复的方式进行维修,在空气环境中开展了S32101双相不锈钢激光填丝焊接修复工艺试验研究,焊接工艺及相关参数可以作为水下焊接研究的参考依据.为避免过高激光功率输入损坏焊接辅助装置,在5000~6000 W激光功率的工艺窗口下,对开设的坡口进行了3次填充修复及4次填充修复,对焊缝截面、显微组织、力学性能以及耐腐蚀性能分别进行了研究.在试验过程中,采用了光学显微镜和扫描电镜等,分析了焊接过程中热输入对微观组织转变的影响.同时通过对比不同激光功率下焊缝的拉伸性能和显微硬度,进一步揭示了工艺参数对焊缝力学性能和耐腐蚀性能的具体影响,从而优化了修复工艺的稳定性和可靠性.结果表明,3次填充修复后的焊缝存在气孔以及冶金熔合不良等问题,4次填充修复后的焊缝截面未见气孔缺陷,拉伸试件断在母材位置.层间焊道的预热和再热促使焊缝中奥氏体析出,焊缝中奥氏体含量略高于铁素体含量,平均硬度略低于母材.焊缝中较高含量的Ni元素和Mo元素使得焊缝的耐腐蚀性能优于母材,4次填充修复得到的焊缝满足空气环境中修复质量标准要求.

“双工联动”协作模式在医院服务中的应用探析

随着我国经济的不断发展,人民对医疗服务质量要求不断提高,医学人文关怀逐渐被强化。在此背景下,医务社工与志愿者联动的“双工联动”模式应运而生。本文介绍了“双工联动”模式的国内发展现状,阐述了其优势,列举了其在医院服务中的应用,包括门急诊导医、住院病房服务、临终关怀和社区居民志愿服务等,并提出进一步优化招募培训体系、健全管理制度、建立智慧管理系统、完善志愿者保障机制等方面的建议。以推动医学人文服务持续健康发展,助力“健康中国”战略实施。

空中可重构智能表面辅助的全双工无人机安全通信

针对传统的可重构智能表面(reconfigurable intelligent surface,RIS,也称智能超表面)在无人机辅助安全通信中存在的灵活性不足和系统安全保障能力不强的问题,以及当前无人机半双工通信系统普遍面临的频谱利用率低和通信效率低的挑战,提出了一种空中可重构智能表面(aerial reconfigurable intelligent sur‐face,ARIS)与全双工无人机的双机协同解决方案,旨在提升面对地面窃听者时的通信安全性和效率。联合优化用户通信调度、传输功率、无人机发送的干扰功率及其飞行轨迹,以及ARIS的相移和轨迹,设计了一个旨在最大化最小平均可达安全速率的优化问题,并提出基于交替优化(alternating optimization,AO)、半定松弛(semi-definite relaxation,SDR)技术和连续凸近似(successive convex approximation,SCA)的迭代算法,以获得高质量的次优解。仿真结果验证了ARIS与全双工无人机结合的双机协作方案在提升通信质量和安全性能方面的有效性,展示了其在复杂安全通信环境下的优越性。