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.

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.

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.

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).

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.

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.

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.

Characteristics of microstructure and performance of laser-treated electroless Ni-P/Ni-W-P duplex coatings

Characteristics of microstructures of electroless Ni-P/Ni-W-P duplex coatings were investigated using SEM/EDX and XRD analysis techniques. Microhardness and wear behaviour of the coatings before and after laser crystallization were evaluated by measurements of hardnesses of coating surface and cross-section, and by unlubricated friction and wear experiments. The results indicate that it is possible to prepare electroless Ni-P/Ni-W-P duplex coatings by sequential immersion in two different plating baths. After laser crystallization, the microstructures of electroless Ni-P/Ni-W-P duplex coatings present the characteristics of higher degree of crystallization and larger grain size for outer layer Ni-W-P than inner Ni-P, but outer layer has a higher hardness. The wear resistance of laser-treated duplex coatings in a given process parameter conditions is superior to the as-plated ones. Laser treatment was performed directly in air without argon protection, which provides the possibility for application of industrialized production.

老年脑缺血患者颅外段颈动脉的Duplex、MRA、DSA检查结果分析（附105例报告）

本文报告１０５例老年脑缺血患者作颅外段颈动脉彩色超声（Ｄｕｐｌｅｘ）或／和磁共振造影（ＭＲＡ）、数控减影血管造影（ＤＳＡ）、手术探查的检查结果。甲组短暂性脑缺血（ＴＩＡ）患者７７例，经上述检查发现颈动脉存在不同程度的斑块性狭窄有４４例（５１．１％），乙组脑梗塞恢复后患者２８例，颈动脉存在不同程度狭窄有１４例（５０．０％）。全组１０５例检出颈动脉有斑块性狭窄５８例（５５．２％）。作者在讨论中指出对脑缺血患者的颈动脉病变的筛选检查方法首选为彩色超声扫描。作者认为确诊颈动脉存在７０％以上狭窄者，颈动脉内膜剥脱术是最好的治疗方法。

Time-Hopping Sequence Design for Virtual Full Duplex via Rapid On-Off-Division Duplex

To achieve virtual full-duplex(VFD)communication using half-duplex radios,the rapid on-off-division(RODD)technique has been proposed in recent years.The time-hopping(TH)sequence is critical to controlling self-interference introduced in the paradigm.By constructing the collision model with a symbol level time scale,the periodic collision correlation function properties are introduced as the performance metric for the TH sequence in the RODD system.To achieve the best VFD performance,an optimization-based method for TH sequence design is proposed.In addition,the conventional TH frame structure design for RODD system is improved.Numerical simulations are presented to demonstrate that the proposed approach can significantly increase system performance.Results indicate that the TH sequence design is very effective for the RODD system.

Analysis of RF Feedback Chain Isolation in Wireless Co-Time Co-Frequency Full Duplex

By employing a radio frequency(RF) feedback chain, the self-interference can be canceled efficiently in co-time co-frequency full duplex(CCFD). However, the evitable signal crosstalk which is caused by the imperfect RF feedback chain isolation usually damages the self-interference cancelation(SIC) performance. To deal with this problem, firstly, we analyze the impact of RF feedback chain isolation on SIC performance. Then a digital preprocessing scheme with RF feedback chain is proposed in the multiple-antenna CCFD architecture. Using both analytical and experimental methods, we find that the proposed scheme achieves a better performance on SIC.

Identification of Orientia tsutsugamushi,spotted fever group and typhus group Rickettsia by duplex and nested PCR methods

Objective:To identify members of genera of rickettsia and O.tsutsugammhi simultaneously.Methods:Rapid and duplex and nested PCR methods have been established by designing primers based on the conserved regions of heat shock protein GroEL gene.345 mouse viscera samples including liver,spleen and kidney,96 Xenopsylla cheopis and 32 chiggers collected from Hongta areas of Yuxi city,Yunnan province were tested by the new PCR methods.Results:The result of the study showed that the new PCR methods could identify most members of genera -Rickettsia and Orientia simultaneously with 100%specificity and its sensitivity could test one copy per microliter.The results of detection prevalence of rickettsioses in mouse,flea and mites DNA samples showed that the total rickettsia infection rate in mouse was 34.78%(120/345).The total infection rates in R.typhi,O.t Karp and R.sibirica of mouse samples were 28.12%(97/345),19.71%(68/345) and O. 29%(1/345) respectively.Co-infection rates in R.typhi and 0.t Karp of mouse samples were 13.33%(46/ 345).O.t Karp type has been the main epidemic strain in these areas.Conclusion:We concluded that this PCR method could be used to detect multi-genera rickettsia simultaneously.Molecular evidences provided in this and previous studies strongly support that Hongta areas of Yuxi city are a natural focus for typhus and scrub typhus with the common occurrence of their confection.

Duplex PCR快速检测松材线虫

利用duplexPCR技术对松材线虫 (Bursaphelenchusxylophilus)与拟松材线虫 (B .mu cronatus)的rDNA部分核苷酸序列扩增。根据松材线虫与拟松材线虫的ITS1序列区别 ,设计出特异性引物 ,检测松材线虫的存在 ;在 5 8S ,2 8S保守序列区设计通用引物 。

Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

The hot deformation characteristics of 1.4462 duplex stainless steel （DSS） were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100~C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-HoUomon parameter （Z） increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6. x 1015 （lnZ---35.5）, a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction （EBSD） confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.

Effect of Temperature and Cl^- Concentration on Pitting of 2205 Duplex Stainless Steel

The electrochemical behaviors of 2205 duplex stainless steel in NaCl solution with different temperatures and concentrations were studied by gravimetric tests, potentiodynamic polarization, electrochemical impedance spectroscopy and scanning electron microscopy. The experinental results show that temperature and chloride concentration have a great influence on the pitting resistance of 2205 duplex stainless steels. They not only effect the corrosion rate of pitting, but also change the shape of the pits. When NaCl solution was in low concentration and temperature below the critical pitting temperature, pits were very small and scattered with hemisphere-like shape. On the contrary, the pits of 2205 duplex stainless steel were large and sometimes had a lacy cover when the NaCl concentration was higher and the temperature was 70℃.

A duplex PCR for the rapid and simultaneous detection of Brucella spp.in human blood samples

Objective:To design a duplex PCR for rapid and simultaneous detection of Brucella species, in human blood samples.Methods:Fifty-two peripheral bloods samples were collected from suspicious patients with brucellosis.Following DNA extraction,PCR assay were performed, using three primers that could simultaneously identify and differentiate three major species of pathogenic Brucella in humans and animals.Results:Of the 52 peripheral bloods samples tested, 25 sample(48%) showed positive reactions in PCR.Twelve samples were positive for Brucella abortus(B.abortus)(23%,13 for Brucella melUensis(B.melUensis)(25%) and 0 for Brucella ovis (6.ovis)(Ow.Conclusions:This work de=monstrates dial in case where specific primers were utilized,duplex PCR has proved to be a simple,fast,and relatively inexpensive method for simultaneous detection of important species of Brucella in clinical samples.

Optimization of process parameters of the activated tungsten inert gas welding for aspect ratio of UNS S32205 duplex stainless steel welds

The activated TIG(ATIG) welding process mainly focuses on increasing the depth of penetration and the reduction in the width of weld bead has not been paid much attention.The shape of a weld in terms of its width-to-depth ratio known as aspect ratio has a marked influence on its solidification cracking tendency.The major influencing ATIG welding parameters,such as electrode gap,travel speed,current and voltage,that aid in controlling the aspect ratio of DSS joints,must be optimized to obtain desirable aspect ratio for DSS joints.Hence in this study,the above parameters of ATIG welding for aspect ratio of ASTM/UNS S32205 DSS welds are optimized by using Taguchi orthogonal array(OA)experimental design and other statistical tools such as Analysis of Variance(ANOVA) and Pooled ANOVA techniques.The optimum process parameters are found to be 1 mm electrode gap,130 mm/min travel speed,140 A current and 12 V voltage.The aspect ratio and the ferrite content for the DSS joints fabricated using the optimized ATIG parameters are found to be well within the acceptable range and there is no macroscopically evident solidification cracking.

The Full-Duplex Artificial Noise Scheme for Security of a Cellular System

This paper focuses on the problem of secure transmission in a cellular system. A full-duplex base station using artificial noise is adopted to improve both the uplink and downlink secrecy rate via pairing terminals which reverses the downlink and uplink of each other. We give the designs of artificial noise and the user's desired signal, and derive the pairing prin-ciple between terminals. Moreover, the influence of self-interference cancellation on secrecy rate is ex-plored. Simulation results show that the secrecy rate can get much better performance by adopting full-duplex artificial noise scheme and proposed pair-ing method. The downlink secrecy rate decreases with the distance between terminals. Besides the uplink secrecy rate is sensitive to the ability of self-interference cancellation.