Magnetic properties and promising cryogenic magneto-caloric performances of Gd_(20)Ho_(20)Tm_(20)Cu_(20)Ni_(20) amorphous ribbons

The magnetic cooling utilizing magneto-caloric effect is recognized as promising energy efficiency and environmentally friendly technology.Here we report a systematical study on the microstructures,magnetic properties and cryogenic magneto-caloric performances of the Gd_(20)Ho_(20)Tm_(20)Cu_(20)Ni_(20) amorphous ribbons.It is found that the ribbons reveal a second-order phase transition and are accompanied by a table-shaped magneto-caloric effect.The calculated magneticentropy-change maximum |ΔSM|,temperature averaged entropy change(i.e.,TEC(10)),and refrigerant capacity reach 13.9 J/kg·K,13.84 J/kg-K and 740 J/kg with magnetic field change of 0-7 T,respectively,indicating that the present Gd_(20)Ho_(20)Tm_(20)Cu_(20)Ni_(20) amorphous ribbons are good candidates for magnetic cooling.

Impact of Robinia pseudoacacia stand conversion on soil properties and bacterial community composition in Mount Tai,China

Background:Robinia pseudoacacia is a widely planted pioneer tree species in reforestations on barren mountains in northern China.Because of its nitrogen-fixing ability,it can play a positive role in soil and forest restoration.After clearcutting of planted stands,R.pseudoacacia stands become coppice plantations.The impacts of shifting from seedling to coppice stands on soil bacterial community and soil properties have not been wel described.This study aims to quantify how soil properties and bacterial community composition vary between planted seedling versus coppice stands.Methods:Nine 20 m×20 m plots were randomly selected in seedling and coppice stands.The bulk soil and rhizosphere soil were sampled in summer 2017.Bulk soil was sampled at 10 cm from the soil surface using a soil auger.Rhizosphere soil samples were col ected using a brush.The soil samples were transported to the laboratory for chemical analysis,and bacterial community composition and diversity was obtained through DNA extraction,16 S r RNA gene amplification and high-throughput sequencing.Results:The results showed that,compared to seedling plantations,soil quality decreased significantly in coppice stands,but without affecting soil exchangeable Mg^(2+) and K^(+).Total carbon(C)and nitrogen(N)were lower in the rhizosphere than in bulk soil,whereas nutrient availability showed an opposite trend.The conversion from seedling to coppice plantations was also related to significant differences in soil bacterial community structure and to the reduction of soil bacterialα-diversity.Principal component analysis(PCA)showed that bacterial community composition was similar in both bulk and rhizosphere soils in second-generation coppice plantations.Special y,the conversion from seedling to coppice stands increased the relative abundance of Proteobacteria and Rhizobium,but reduced that of Actinobacteria,which may result in a decline of soil nutrient availability.Mantel tests revealed that C,N,soil organic matter(SOM),nitrate nitrogen(NO^(-)+(3)-N)and available phosphorus positively correlated with bacterial community composition,while a variation partition analysis(VPA)showed that NO^(-)+(3)-N explained a relatively greater proportion of bacterial distribution(15.12%),compared with C and SOM.Surprisingly,N showed no relationship with bacterial community composition,which may be related to nitrogen transportation.Conclusions:The conversion from seedling to coppice stands reduced soil quality and led to spatial-temporal homogenization of the soil bacterial community structure in both the rhizosphere and bulk soils.Such imbalance in microbial structure can accelerate the decline of R.pseudoacacia.This may affect the role of R.pseudoacacia coppice stands in soil and forest restoration of barren lands in mountain areas.

Multi-Objective Redundancy Optimization of Continuous-Point Robot Milling Path in Shipbuilding

The 6-DOF manipulator provides a new option for traditional shipbuilding for its advantages of vast working space,low power consumption,and excellent flexibility.However,the rotation of the end effector along the tool axis is functionally redundant when using a robotic arm for five-axis machining.In the process of ship construction,the performance of the parts’protective coating needs to bemachined tomeet the Performance Standard of Protective Coatings(PSPC).The arbitrary redundancy configuration in path planning will result in drastic fluctuations in the robot joint angle,greatly reducing machining quality and efficiency.There have been some studies on singleobjective optimization of redundant variables,However,the quality and efficiency of milling are not affected by a single factor,it is usually influenced by several factors,such as the manipulator stiffness,the joint motion smoothness,and the energy consumption.To solve this problem,this paper proposed a new path optimization method for the industrial robot when it is used for five-axis machining.The path smoothness performance index and the energy consumption index are established based on the joint acceleration and the joint velocity,respectively.The path planning issue is formulated as a constrained multi-objective optimization problem by taking into account the constraints of joint limits and singularity avoidance.Then,the path is split into multiple segments for optimization to avoid the slow convergence rate caused by the high dimension.An algorithm combining the non-dominated sorting genetic algorithm(NSGA-II)and the differential evolution(DE)algorithm is employed to solve the above optimization problem.The simulations validate the effectiveness of the algorithm,showing the improvement of smoothness and the reduction of energy consumption.

Real-Time Visual Tracking with Compact Shape and Color Feature

The colour feature is often used in the object tracking.The tracking methods extract the colour features of the object and the background,and distinguish them by a classifier.However,these existing methods simply use the colour information of the target pixels and do not consider the shape feature of the target,so that the description capability of the feature is weak.Moreover,incorporating shape information often leads to large feature dimension,which is not conducive to real-time object tracking.Recently,the emergence of visual tracking methods based on deep learning has also greatly increased the demand for computing resources of the algorithm.In this paper,we propose a real-time visual tracking method with compact shape and colour feature,which forms low dimensional compact shape and colour feature by fusing the shape and colour characteristics of the candidate object region,and reduces the dimensionality of the combined feature through the Hash function.The structural classification function is trained and updated online with dynamic data flow for adapting to the new frames.Further,the classification and prediction of the object are carried out with structured classification function.The experimental results demonstrate that the proposed tracker performs superiorly against several state-of-the-art algorithms on the challenging benchmark dataset OTB-100 and OTB-13.

Table-like shape magnetocaloric effect and large refrigerant capacity in dual-phase HoNi/HoNi2 composite

Nowadays,magnetic cooling(MC) technology by using the magnetocaloric effect(MCE) has attracted extensive research interest for its promising practical applications.A constant large/giant MCE covers wide refrigeration temperatures(denote as table-like shape) is beneficial for obtaining high efficiency performance for MC.In this paper,the HoNi/HoNi2 composite was successfully synthesized by arc-melting method and proved to be composed of HoNi and HoNi2 crystalline phases with weight ratios of 52.4 wt.% and 47.6 wt.%,respectively.The maximum magnetic entropy change(-ΔSMmax)is 18.23 J/(kg·K),and the refrigerant capacity values RC1,RC2,and RC3 are 867.9 J/kg,676.4 J/kg,and 467.8 J/kg with ΔH=0-70 kOe,respectively.The table-like shape MCE and large refrigerant capacity values make the composite attractive for cryogenic MC using the Ericsson cycle.

Operando investigation of particle re-entrainment mechanism in electrostatic capture process on the lab-on-a-chip

Inhalable particle is a harmful air pollutant that causes a significant threat to people's health and ecological environments,which should be removed to purify air,but there exists limited removal efficiency due to particle re-entrainment.Here,Operando observation system based on microscopic visualization method is developed to make in situ test of particle migration,deposition and re-entrainment characteristics on a lab-on-a-chip to achieve the investigation in micro-level scale.The deposition evolution of charged particles is recorded in electric field region intuitively,which confirms the fracture of particle chain occurs during the growth process of deposited particles.It captures the instantaneous process that a larger particle with micron size due to the coagulation of submicron particles fractures from main body of the particle chain for the first time.The analysis of migration behavior of a single submicron particle near electrode surface demonstrates the direct influence of drag force on the fracture of particle chain.This work is the first-time visualization of dynamic process and mechanism elucidation of particle re-entrainment at the micron level,and the findings will provide the theory support for the particle re-entrainment mechanism and bring inspires of enhancing capture efficiency of inhalable particle.

Four-dimensional direct detection receiver enabling Jones-space field recovery with phase and polarization diversity

Data centers,the engines of the global Internet,rely on powerful high-speed optical interconnects.In optical fiber communication,classic direct detection captures only the intensity of the optical field,while the coherent detection counterpart utilizes both phase and polarization diversities at the expense of requiring a narrow-linewidth and high-stability local oscillator(LO).Herein,we propose and demonstrate a four-dimensional Jones-space optical field recovery(4-D JSFR)scheme without an LO.The polarization-diverse full-field receiver structure captures information encoded in the intensity and phase of both polarizations,which can be subsequently extracted digitally.To our knowledge,our proposed receiver achieves the highest electrical spectral efficiency among existing direct detection systems and potentially provides similar electrical spectral efficiency as standard intradyne coherent detection systems.The fully recovered optical field extends the transmission distance beyond the limitations imposed by fiber chromatic dispersion.Moreover,the LO-free advantage makes 4-D JSFR suitable for photonic integration,offering a spectrally efficient and cost-effective solution for massively parallel data center interconnects.Our results may contribute to the ongoing developments in the theory of optical field recovery and the potential design considerations for future high-speed optical transceivers.

Achievement of giant cryogenic refrigerant capacity in quinary rare-earths based high-entropy amorphous alloy

Magnetic refrigeration(MR)by utilizing the magnetocaloric(MC)effect is recognized as one of the most potential promising solid state environmentally friendly and high efficiency alternative method to the well-used state-of-the-art gas compression cooling technique.In this work,a systematic investigation of quinary equi-atomic rare-earths(RE)based Er_(20) Ho_(20) Gd_(20) Ni_(20) Co_(20) high-entropy(HE)amorphous alloy in terms of the microstructure,magnetic and magnetocaloric(MC)properties have been reported.The Er_(20) Ho_(20) Gd_(20) Ni_(20) Co_(20) exhibits promising glass forming ability with an undercooled liquid region of 72 K.Excellent cryogenic MC performances can be found in wide temperature from∼25 and∼75 K,close to H_(2) and N_(2) liquefaction,respectively.Apart from the largest magnetic entropy change(-S M)reaches 17.84 J/(kg K)with 0-7 T magnetic field change,corresponding refrigerant capacity(RC)attains a giant value of 1030 J/kg.The promising cryogenic MC performances together with the unique HE amorphous characterizations make the quinary Er_(20) Ho_(20) Gd_(20) Ni_(20) Co_(20) HE amorphous alloy attractive for cryogenic MR applications.

Magnetic properties and promising magnetocaloric performances in the antiferromagnetic GdFe_(2)Si_(2)compound

The magnetocaloric(MC) effect-based solidstate magnetic refrigeration(MR) technology has been recognized as an alternative novel method to the presently commercialized gas compression technology. Searching for suitable candidates with promising MC performances is one of the most urgent tasks. Herein, combined experimental and theoretical investigations on the magnetic properties, magnetic phase transition, and cryogenic MC performances of Gd Fe_(2)Si_(2)have been performed. An unstable antiferromagnetic(AFM) interaction in the ground state has been confirmed in Gd Fe_(2)Si_(2). Moreover, a huge reversible cryogenic MC effect and promising MC performances in Gd Fe_(2)Si_(2)have been observed.The maximum isothermal magnetic entropy change, temperature-averaged entropy change with 2 K lift, and refrigerant capacity for Gd Fe_(2)Si_(2)were 30.01 J kg^(-1)K^(-1),29.37 J kg^(-1)K^(-1), and 328.45 J kg^(-1)at around 8.6 K with the magnetic change of 0–7 T, respectively. Evidently, the values of these MC parameters for the present AFM compound Gd Fe_(2)Si_(2)are superior to those of most recently reported rareearth-based MC materials, suggesting the potential application for active cryogenic MR.

First-and second-order phase transitions in RE_(6)Co_(2)Ga(RE=Ho,Dy or Gd)cryogenic magnetocaloric materials

Rare-earth(RE)rich intermetallics crystallizing in orthorhombic Ho_(6)Co_(2)Ga-type crystal structure exhibit peculiar magnetic properties that are not widely reported for their magnetic ordering,order of magnetic phase transition,and related magnetocaloric behavior.By tuning the type of RE element in RE_(6)Co_(2)Ga(RE=Ho,Dy or Gd)compounds,metamagnetic anti-to-paramagnetic(AF to PM)phase transitions could be tuned to ferro-to-paramagnetic(FM to PM)phase transitions.Furthermore,the FM ground state for Gd_(6)Co_(2)Ga is confirmed by density functional theory calculations in addition to experimental observations.The field dependence magnetocaloric and Banerjee’s criteria demonstrate that Ho_(6)Co_(2)Ga and Dy_(6)Co_(2)Ga undergo a first-order phase transition in addition to a second-order phase transition,whereas only the latter is observed for Gd_(6)Co_(2)Ga.The two extreme alloys of the series,Ho_(6)Co_(2)Ga and Gd_(6)Co_(2)Ga,show maximum isothermal entropy change(|ΔS_(iso)^(max)(5T)|)of 10.1 and 9.1 J kg^(-1)K^(-1)at 26 and 75 K,close to H_(2)and N_(2)liquefaction,respectively.This outstanding magnetocaloric effect performance makes the RE6 Co_(2)Ga series of potential for cryogenic magnetic refrigeration applications.

重稀土HRENiGa_(2)(HRE=Dy,Ho或Er)化合物的优异低温磁热性能

RENiX_(2)化合物(其中RE为稀土元素,X为p区元素)在低温磁制冷应用中受到高度关注.它们根据元素的不同可以结晶成CeNiSi_(2)型、NdNiGa_(2)型或MgCuAl_(2)型晶体结构,并表现出不同类型的磁有序性从而影响其磁性.MgCuAl_(2)型铝化物由于具有有利的铁磁基态从而表现出比CeNiSi_(2)型硅化物和NdNiGa_(2)型镓化物更大的磁热性能.此外,RENiGa_(2)镓化物根据RE元素的不同可以结晶成NdNiGa_(2)或MgCu Al_(2)型结构.本文中,我们选择重稀土(HRE)元素来探索HRENiGa_(2)(HRE=Dy,Ho或Er)镓化物的微观结构、磁有序和磁热性能.三种化合物均以MgCuAl_(2)型晶体结构结晶,并且随着温度的升高经历了从铁磁到顺磁的二级磁相转变.DyNiGa_(2),HoNiGa_(2)和ErNiGa_(2)化合物的最大等温磁熵变(|ΔSisomax|)值分别为6.2,10.4和11.4 J kg^(-1)K^(-1)(0-5T),这与许多最近报道的低温磁制冷材料性能相当.特别地,HoNiGa_(2)和ErNiGa_(2)化合物(包括它们的复合材料)在氢气液化的温度范围内表现出优异的磁热性能.

Exploration of the rare-earth cobalt nickel-based magnetocaloric materials for hydrogen liquefaction

Magnetic refrigeration based on the magnetocaloric effect(MCE)of magnetic solids has been considered as an emerging technology for hydrogen liquefaction.However,the lack of high-performance materials has slowed the development of any practical applications.Here,we present a family of rare-earth cobalt nickel-based magnetocaloric materials,namely Dy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds,and system-atically investigated their structural and magnetic properties as well as the MCE and magnetocaloric per-formance.All of these compounds crystallize in the C15-type Laves-phase structure and undergo typi-cal second-order magnetic phase transition(MPT).The change in magnetism and the MPT temperature for the Dy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds originate from the exchange interactions between nearest-neighbor RE 3+ion pairs.No hysteresis magnetocaloric effect was achieved,and the MPT tem-perature of these compounds could be tuned from the liquefaction temperature of nitrogen(∼77 K)to hydrogen(∼20 K)by adjusting the ratio of rare-earth elements.This study’s findings indicate that theDy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds are of potential for practical magnetic refrigeration applica-tions in the field of hydrogen liquefaction.

RE-NiO_(x)(RE=Ce,Y,La)composite oxides coupled plasma catalysis for benzene oxidation and by-product ozone removal

Plasma-coupled catalysis is a promising volatile organic co mpounds(VOCs) removal technology because of its interactional principles of plasma decomposition and catalytic oxidation.However,the problem of harmful by-products is still in trouble.A series of rare earth doped RE-NiO_(x)(RE=Ce,Y,La) composite oxides were synthesized by metal organic frameworks(MOFs)-derived method for coupled plasma oxidation of benzene and by-product ozone removal.Compared with plasma alone,the 1%La-NiO_(x)catalyst shows the best enhancement of 50% for benzene conversion with complete removal of a maximum of 800 ppm ozone.The energy consumption for 90% benzene removal efficiency(η90%) is also reduced from 3600 to 1200 J/L.Characterization re sults of RE-NiO_(x) catalysts indicate that the doping of La causes interaction and synergistic effect between La and Ni,and the surface oxygen and lattice oxygen with defects play crucial roles in benzene oxidation and ozone decomposition,respectively.In addition,the decomposition mechanism of benzene and ozone under plasma is proposed.Plasma is responsible for the indiscriminate bond breaking in benzene and oxygen to form a variety of organic intermediates and ozone,while the La-NiO_(x) catalyst selectively oxidizes the intermediates to CO_(x)/H2O and decomposes the ozone into oxygen.