Tulipa iliensis,as a wild plant resource,possesses high ornamental value and can provide abundant parental materials for tulip breeding.The objective of this research was to forecast the worldwide geographical spread ...Tulipa iliensis,as a wild plant resource,possesses high ornamental value and can provide abundant parental materials for tulip breeding.The objective of this research was to forecast the worldwide geographical spread of Tulipa iliensis by considering bioclimatic,soil,and topographic variables,the findings of this research can act as a benchmark for the conservation,management,and utilization of Tulipa iliensis as a wild plant resource.Research results indicate that all 12 models have an area under curve(AUC)of the receiver operating characteristic curve(ROC)values greater than 0.968 for the paleoclimatic,current,and future climate scenarios,this suggests an exceptionally high level of predictive accuracy for the models.The distribution of Tulipa iliensis is influenced by several key factors.These factors include the mean temperature of the driest quarter(Bio9),calcium carbonate content(T_CACO3),slope,precipitation of the driest month(Bio14),Basic saturation(T_BS),and precipitation of the coldest quarter(Bio19).During the three paleoclimate climate scenarios,the appropriate habitats for Tulipa iliensis showed a pattern of expansion-contraction expansion.Furthermore,the total suitable area accounted for 13.38%,12.28%,and 13.28%of the mainland area,respectively.According to the current climate scenario,the High-suitability area covers 61.78472×10^(4)km^(2),which accounts for 6.57%of the total suitable area,The Midsuitability area covers 190.0938×10^(4)km^(2),accounting for 20.2%of the total suitable area,this represents a decrease of 63.53%~67.13%compared to the suitable area of Tulipa iliensis under the paleoclimate scenario.Under the Shared Socioeconomic Pathways(SSP)scenarios,in 2050 and 2090,Tulipa iliensis is projected to experience a decrease in the High,Mid,and Low-suitability areas under the SSP126 climate scenario by 7.10%~12.96%,2.96%~4.27%and 4.80%~7.96%,respectively.According to the SSP245 scenario,the high suitability area experienced a slight expansion of 2.26%in 2050,but a reduction of 6.32%in 2090.In the SSP370 scenario,the High-suitability areas had a larger reduction rate of 11.24%in 2050,while the Mid-suitability and Low-suitability areas had smaller expansion rates of 0.36%and 4.86%,respectively.In 2090,the High-suitability area decreased by 4.84%,while the Mid and Low-suitability areas experienced significant expansions of 15.73%and 45.89%,respectively.According to the SSP585 scenario,in the future,the High,Mid,and Low-suitability areas are projected to increase by 5.09%~7.21%,7.57%~17.66%,and 12.30%~48.98%,respectively.The research offers enhanced theoretical direction for preserving Tulipa iliensis’genetic variety amidst evolving climatic scenarios.展开更多
Macroscopic magnetic properties of magnets strongly depend on the magnetization process and the microstructure of the magnets.Complex materials such as hard-soft exchange-coupled magnets or just real technical materia...Macroscopic magnetic properties of magnets strongly depend on the magnetization process and the microstructure of the magnets.Complex materials such as hard-soft exchange-coupled magnets or just real technical materials with impurities and inhomogeneities exhibit complex magnetization behavior.Here we investigate the effects of size,volume fraction,and surroundings of inhomogeneities on the magnetic properties of an inhomogeneous magnetic material via micromagnetic simulations.The underlying magnetization reversal and coercivity mechanisms are revealed.Three different demagnetization characteristics corresponding to the exchange coupling phase,semi-coupled phase,and decoupled phase are found,depending on the size of inhomogeneities.In addition,the increase in the size of inhomogeneities leads to a transition of the coercivity mechanism from nucleation to pinning.This work could be useful for optimizing the magnetic properties of both exchange-coupled nanomagnets and inhomogeneous single-phase magnets.展开更多
A novel adaptive sampling interval algorithm for multitarget tracking is presented. This algorithm which is based on interacting multiple models incorporates the grey relational grade （GRG） into the particle swarm o...A novel adaptive sampling interval algorithm for multitarget tracking is presented. This algorithm which is based on interacting multiple models incorporates the grey relational grade （GRG） into the particle swarm optimization （PSO）. Firstly, the desired tracking accuracy is set for each target. Secondly, sampling intervals are selected as particles, and then the advantage of the GRG is taken as the measurement function for resource management. Meanwhile, the fitness value of the PSO is used to measure the difference between desired tracking accuracy and estimated tracking accuracy. Finally, it is suggested that the radar should track the target whose prediction value of the next sampling interval is the smallest. Simulations show that the proposed method improves both the tracking accuracy and tracking efficiency of the phased-array radar.展开更多
Transient brain ischemia has been shown to induce hyperphosphorylation of the micro- tubule-associated protein tau. To further determine the mechanisms underlying these processes, we investigated the interaction betwe...Transient brain ischemia has been shown to induce hyperphosphorylation of the micro- tubule-associated protein tau. To further determine the mechanisms underlying these processes, we investigated the interaction between tau, glycogen synthase kinase （GSK）-313 and protein phos- phatase 2A. The results confirmed that tau protein was dephosphorylated during brain ischemia; in addition, the activity of GSK-3β was increased and the activity of protein phosphatase 2A was de- creased. After reperfusion, tau protein was hyperphosphorylated, the activity of GSK-3β was de- creased and the activity of protein phosphatase 2A remained low. Importantly, the interaction of tau with GSK-3β and protein phosphatase 2A was altered during ischemia and reperfusion. Lithium chloride could affect tau phosphorylation by regulating the interaction of tau with GSK-3β and pro- tein phosphatase 2A, and improve learning and memory ability of rats after transient brain ischemia. The present study demonstrated that it was the interaction of tau with GSK-3β and protein phos- phatase 2A, rather than their individual activities, that dominates the phosphorylation of tau in tran- sient brain ischemia. Hyperphosphorylated tau protein may play an important role in the evolution of brain injury in ischemic stroke. The neuroprotective effects of lithium chloride partly depend on the inhibition of tau phosphorylation during transient brain ischemia.展开更多
Significant efforts have been put into the recycling of bulk Nd–Fe–B sintered magnet wastes around the world in the past decade because bulk Nd–Fe–B sintered magnet wastes are valuable secondary rare-earth resourc...Significant efforts have been put into the recycling of bulk Nd–Fe–B sintered magnet wastes around the world in the past decade because bulk Nd–Fe–B sintered magnet wastes are valuable secondary rare-earth resources.There are two major facts behind the efforts.First, the waste magnets contain total rare-earth content as high as more than 30 wt.%, which is higher than most natural rare-earth mines.Second, the waste magnets maintain the physical and chemical properties of the original magnets even with deterioration of the properties on surfaces due to corrosion and contamination.In this review,various techniques for recycling bulk Nd–Fe–B sintered magnet wastes, the overall properties of the recycled Nd–Fe–B sintered magnets, and the mass production of recycled magnets from the wastes are reviewed.展开更多
[Objectives]This study was conducted to optimize the extraction process of Sipunculus nudus polysaccharide and study the antioxidant activity of S. nudus polysaccharide. [Methods] S. nudus polysaccharide was extracted...[Objectives]This study was conducted to optimize the extraction process of Sipunculus nudus polysaccharide and study the antioxidant activity of S. nudus polysaccharide. [Methods] S. nudus polysaccharide was extracted by ultrasonic microwave assisted method,during which univariate factors including solidliquid ratio,time,temperature,ultrasonic power,microwave power were investigated,to select optimal extracting conditions,which were also verified by an response surface optimization experiment( an four-factor three-level test); and the antioxidant activity of S. nudus polysaccharide was studied by determining its DPPH radical scavenging capacity. [Results]Through univariate factor investigation and response surface optimization test,it was found that the response surface results were consistent with univariate results. The optimized conditions were as follows: solid-liquid ratio at 1∶ 15,ultrasonic temperature at 60 ℃,ultrasonic power of 360 W and microwave power of 200 W,and the predicted polysaccharide extracting amount was 4. 35 mg/g. Under the optimized extracting conditions,the average extracting amount of S. nudus polysaccharide was 4. 38 mg/g,which is close to the theoretical predicted value( 4. 35 mg/g). And the results of this study also showed that different concentrations of polysaccharide solutions have different scavenging effects on DPPH free radical. At the polysaccharide concentration of0. 16 mg/ml,the maximum value of DPPH radical scavenging rate was 7. 22%,indicating that polysaccharide has certain antioxidant capacity. [Conclusions]This method is a new trial with satisfactory results.展开更多
Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques,it is urgent to develop an efficient recycling technique for ...Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques,it is urgent to develop an efficient recycling technique for leftover sludge from the manufacturing process of neodymium-iron-boron(Nd-Fe-B)sintered magnets.In the present study,centerless grinding sludge from the Nd-Fe-B sintered magnet machining process was selected as the starting material.The sludge was subjected to a reduction-diffusion(RD)process in order to synthesize recycled neodymium magnet(Nd2Fe14B)powder;during this process,most of the valuable elements,including neodymium(Nd),praseodymium(Pr),gadolinium(Gd),dysprosium(Dy),holmium(Ho),and cobalt(Co),were recovered simultaneously.Calcium chloride(CaCl2)powder with a lower melting point was introduced into the RD process to reduce recycling cost and improve recycling efficiency.The mechanism of the reactions was investigated systematically by adjusting the reaction temperature and calcium/sludge weight ratio.It was found that single-phase Nd2Fe14B particles with good crystallinity were obtained when the calcium weight ratio(calcium/sludge)and reaction temperature were 40 wt% and 1050℃,respectively.The recovered Nd2Fe14B particles were blended with 37.7 wt% Nd4Fe14B powder to fabricate Nd-Fe-B sintered magnets with a remanence of 12.1 kG(1 G=1×10^-4T),and a coercivity of 14.6 kOe(1 Oe=79.6A·m^-1),resulting in an energy product of 34.5 MGOe.This recycling route promises a great advantage in recycling efficiency as well as in cost.展开更多
Shallow conductive heterogeneity can lead to static shifts ain the apparent resistivity sounding curve of controlled-source audio-frequency magnetotellurics(CSAMT).The static effect will shift the apparent resistivity...Shallow conductive heterogeneity can lead to static shifts ain the apparent resistivity sounding curve of controlled-source audio-frequency magnetotellurics(CSAMT).The static effect will shift the apparent resistivity curves along with axial log-log coordinates.Such an effect,if not properly processed,can distort the resistivity of rock formation and the depth of interfaces,and even make the geological structures unrecognizable.In this paper,we discuss the reasons and characteristics of the static shift and summarize the previous studies regarding static shift correction.Then,we propose the Guided Image Filtering algorithm to suppress static shifts in CSAMT.In detail,we use the multi-window superposition method to superimpose 1D signals into a 2D matrix image,which is subsequently processed with Guided Image Filtering.In the synthetic model study and field examples,the Guided Image Filtering algorithm has effectively corrected and suppressed static shifts,and finally improved the precision of data interpretation.展开更多
The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bu...The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bulk material,which could be benefited from pulsed neutron source.Here we build a Bragg-edge imaging system on the General Purpose Powder Diffractometer at the China Spallation Neutron Source.The residual strain mapping of a bent Q235 ferrite steel sample has been achieved with a spectral resolution of 0.15%by the time-of-flight neutron Bragg-edge imaging on this system.The results show its great potential applications in materials science and engineering.展开更多
As a new choice for the treatment of degenerative lumbar disease, artificial lumbar disc replacement has been widely used in clinical surgery. The finite element is a very effective method to predict and simulate the ...As a new choice for the treatment of degenerative lumbar disease, artificial lumbar disc replacement has been widely used in clinical surgery. The finite element is a very effective method to predict and simulate the surgery effect. The purpose of this paper is to review the applications of finite element in artificial lumbar disc replacement, such as design of artificial lumbar disc prosthesis, risk and effect evaluation of artificial lumbar disc replacement, and assessment of operation methods. Lastly, we discuss the future development of finite element method applied in this field, including personalized design of the prosthesis, postoperative behavior guide, and artificial lumbar disc replacement combined with fusion surgery. In conclusion, as an invaluable complement to biomechanical experiments and clinical studies, the finite element method makes important contributions to our understanding of biomechanics of intervertebral disc, and plays an important role in the field of artificial lumbar disc replacement.展开更多
Many researches point out that intervertebral pressure and transformation are key parameters for evaluating intervertebral disc degeneration. Aiming at avoiding the damage caused by direct and indirect measuring metho...Many researches point out that intervertebral pressure and transformation are key parameters for evaluating intervertebral disc degeneration. Aiming at avoiding the damage caused by direct and indirect measuring methods, this research proposes a cylindroid hypothesis and measuring method, which can monitor the strain condition of the intervertebral disc in vivo and real-time without being damaged.展开更多
The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a cos...The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a costeffective reduction-diffusion method.The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm_(2)Fe_(17).The effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated.Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles.By employing the strategy of adding 20 wt% of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm_(2)Fe_(17) particles that are well-dispersed,with an average size of 2.2 μm.Furthermore,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm_(2)Fe_(17)N_(3) material was successfully obtained.This study could be useful for the development of high-performance Sm_(2)Fe_(17)N_(3) magnetic materials utilizing reduction-diffusion technology.展开更多
Due to its large magnetocrystalline anisotropy field and high Curie temperature,SmCo-based magnets are irreplaceable in high-temperature applications,The hot-deformed SmCo-based magnets are especially attractive for t...Due to its large magnetocrystalline anisotropy field and high Curie temperature,SmCo-based magnets are irreplaceable in high-temperature applications,The hot-deformed SmCo-based magnets are especially attractive for their excellent corrosion resistance,making them more suitable for harsh environments.However,it is still challenging for hot-deformed SmCo-based magnets to obtain high magnetization and high coercivity simultaneously.Therefore,it is necessary to analyze the relationship between its microstructure and magnetic properties and explore its magnetic hardening mechanism to guide the further improvement of magnetic properties.In this paper,the anisotropic heterostructure SmCo_(5)magnet was prepared by combining large height-reduction and introducing a nano-grained Smrich phase.Strong c-axis texture,(BH)m of 16.1 MGOe,and H_(ci)of 9.6 kOe were obtained via the heterostructure with SmCo_(5)micron-grain and Sm-rich nano-scale precipitates.The magnetic domain observation and technical magnetization analysis demonstrate that the coe rcivity mechanism is dominated by nucleation.The results also show that the smooth and Sm-rich precipitated grain boundary provides weak pinning effects.It provides a reference for the development of high-pe rformance nanocrystalline SmCo_(5)magnets.展开更多
Nanocomposite permanent magnets have ultra-high theoretical magnetic energy products,due to cou-pling of the soft/hard magnetic phases,inciting strict microstructural requirements.In this study,the microstructure evol...Nanocomposite permanent magnets have ultra-high theoretical magnetic energy products,due to cou-pling of the soft/hard magnetic phases,inciting strict microstructural requirements.In this study,the microstructure evolution,including the phase transition,morphological changes,and texture formation,of hot-deformed SmCo-based nanocomposites under thermal-stress-strain coupling was characterized to determine a possible strategy for achieving high performance.The SmCo_(5)/α-Fe nanocomposites precursor contained fine and dispersed Sm(Fe,Co)_(5)and Fe-Co grains and exhibited a two-stage phase transforma-tion accompanied by grain growth.In the early stage of deformation at relatively low temperature,the adjacent Sm(Co,Fe)5 and Fe-Co phase formed the Sm_(2)(Co,Fe)_(17)-H phase,which was stable only with small grain sizes.In the high-temperature deformation stage,the Sm_(2)(Co,Fe)_(17)-H phase transformed into the Sm_(2)(Co,Fe)_(17)-R phase with large grain sizes.In addition,the strong c-axis texture formed in the Sm(Co,Fe)_(5)phase but not in the Sm_(2)(Co,Fe)_(17)-R phase.Subsequently,the phase transition process and texture formation mechanism were systematically analyzed by transmission electron microscopy.The ini-tiation of a slip system and/or preferential grain growth explained the formation of texture under the action of uniform stress and strain and assisted by dispersed Sm-rich nanograins.The Sm_(2)(Co,Fe)_(17)-R grains with poor orientations and large grain sizes did not achieve magnetic hardening,which also dam-age the magnetic properties.According to the results of this work,we also presented a new strategy to prepare high-performance SmCo-based nanocomposites magnets.展开更多
In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-...In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-selective dissolution washing proc ess.The chemo-selective dissolution effect of various solution(deionized water,dilute acetic acid solution,NH_(4)Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder.The NH_(4)Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase.Besides,the optimal NH_(4)Cl concentration and liquid-to-solid ratio were investigated.As a consequence,the contents of Ca,O,and H after optimal washing process are reduced to 0.07 wt%,0.31 wt% and 0.22 wt%,respectively.Hence,M_(3) Tis increased to 146.72 emu/g,which is 33% higher than that of the initial sludge.Then,the regenerated Nd-Fe-B sintered magnets with properties of B_(r)=11.66 kG,H_(cj)=16.49 kOe,and(BH)_(m)=31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders.Compared with the corresponding regenerated magnets washed with deionized water,the remanence and coercivity are increased by 18% and 59%,respectively.展开更多
Environmental friendly recycling process for Nd-Fe-B sintered magnet sludges generated in the manufacturing process, which contain large amount of rare earth, including Nd, Pr and Dy, is badly needed so far. In presen...Environmental friendly recycling process for Nd-Fe-B sintered magnet sludges generated in the manufacturing process, which contain large amount of rare earth, including Nd, Pr and Dy, is badly needed so far. In present study, we have developed an effective route to obtain recycled sintered magnets from Nd-Fe-B sintered magnet sludges by calcium reduction-diffusion(RD) process. Compared to conventional recycling process, our research is focused on recovering most of the useful elements, including Nd, Pr, Dy, Co, and Fe together instead of just rare earth elements. To improve the recycling efficiency and reduce pollution, the co-precipitating parameters were simulated and calculated using MATLAB software. Most of useful elements were recovered by a co-precipitation method, and the obtained composite powders were then directly fabricated as recycled Nd-Fe-B powders by a calcium reduction-diffusion(RD) method. The recovery rates are 98%, 99%, 99%, 93%, and 99%, for Nd, Pr, Dy, Co, and Fe, respectively. The amount of useful elements contained in the recovered composite powders is greater than99.71 wt%. The process of RD for synthesizing NdFeB and subsequently removing CaO was thoroughly investigated. Furthermore, the recycled Nd-Fe-B magnet exhibits a remanence of 1.1 T, a coercivity of1053 kA/m, and an energy product of 235.6 kJ/m~3, respectively, indicating that recycled Nd-Fe-B sintered magnet was successfully recovered from the severely contaminated sludges via an effective recycling route.展开更多
The evolution of the microstructure,microchemistry and magnetic properties of the Sm(CobalFe_(0.28)-CuyZrx)_(7.6)magnets with different Zr and Cu contents was investigated.It is found that the coercivity of the Sm(Co,...The evolution of the microstructure,microchemistry and magnetic properties of the Sm(CobalFe_(0.28)-CuyZrx)_(7.6)magnets with different Zr and Cu contents was investigated.It is found that the coercivity of the Sm(Co,Fe,Cu,Zr)_(z)magnets is sensitive to Zr content.The deficiency of Zr content causes heterogeneity of Cu and Fe distributions,while an excessive Zr content leads to the formation of a SmCoZr impurity phase.The cellular structure and distribution of Cu concentration.gradient between the cell boundary phase and cell pha se are destroyed by inappropriate Zr content,which results in a reduction of coercivity.The Cu concentration difference between the cell boundary phase and cell phase increases with increasing Cu content.The coercivity of the Sm(CobalFe_(0.28)CuyZ_(r0.02))_(7.6)magnets increases from 10.4 to 25.4 kOe for y=0.05 and y=0.07.However,the excess of Cu element destroys the cell boundary phase and enlarges the cell size,resulting in a significant decrease of squareness and energy density.The optimum performance(remanence of 11.4 kG,coercivity of 25.4 kOe,maximum magnetic ene rgy product of 30.4 MGOe)was obtained for the Sm(Co_(0.63)Fe_(0.28)Cu_(0.07)Zr_(0.02))_(7.6)magnet.展开更多
Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti-6Al-4V-xCu （x = 1, 3, 5 wt%）, were fabricated in the present study in order to re...Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti-6Al-4V-xCu （x = 1, 3, 5 wt%）, were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element. The metallography, X-ray diffraction, antibacterial ability, corrosion resistance and cytotoxicity of Ti-6Al-4V-xCu alloys were preliminarily studied with comparison to the commercial medical Ti-6Al-4V alloy. The Ti-6Al- 4V-xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility, and the antibacterial role was enhanced with increasing Cu content, which has significant potential for clinical applications as surgical implant materials.展开更多
In this article,the Sm_(2)Co_(7)/α-Fe nanocomposite magnets were prepared by high energy ball milling and spark plasma sintering method.The effect of soft phase content on the magnetic properties was studied.Up to 30...In this article,the Sm_(2)Co_(7)/α-Fe nanocomposite magnets were prepared by high energy ball milling and spark plasma sintering method.The effect of soft phase content on the magnetic properties was studied.Up to 30 wt% α-Fe was added into Sm_(2)Co_(7) matrix without the decrease of remanence.Optimal energy product(BH)max of 9.2 MGOe was obtained with 20 wt% α-Fe.TEM observation shows that the grain size of α-Fe is 20-50 nm which ensures a good coupling effect between soft and hard phase.One more thing needs to be mentioned is that there exists inter-diffusion between Sm-Co phase and α-Fe phase.Moreover,our results can also illustrate that the Sm_(2)Co_(7)/α-Fe nanocomposite magnets are able to acquire better magnetic properties than the SmCo_(5)/α-Fe magnets prepared by the same process due to the large domain width of Sm_(2)Co_(7) phase.展开更多
文摘Tulipa iliensis,as a wild plant resource,possesses high ornamental value and can provide abundant parental materials for tulip breeding.The objective of this research was to forecast the worldwide geographical spread of Tulipa iliensis by considering bioclimatic,soil,and topographic variables,the findings of this research can act as a benchmark for the conservation,management,and utilization of Tulipa iliensis as a wild plant resource.Research results indicate that all 12 models have an area under curve(AUC)of the receiver operating characteristic curve(ROC)values greater than 0.968 for the paleoclimatic,current,and future climate scenarios,this suggests an exceptionally high level of predictive accuracy for the models.The distribution of Tulipa iliensis is influenced by several key factors.These factors include the mean temperature of the driest quarter(Bio9),calcium carbonate content(T_CACO3),slope,precipitation of the driest month(Bio14),Basic saturation(T_BS),and precipitation of the coldest quarter(Bio19).During the three paleoclimate climate scenarios,the appropriate habitats for Tulipa iliensis showed a pattern of expansion-contraction expansion.Furthermore,the total suitable area accounted for 13.38%,12.28%,and 13.28%of the mainland area,respectively.According to the current climate scenario,the High-suitability area covers 61.78472×10^(4)km^(2),which accounts for 6.57%of the total suitable area,The Midsuitability area covers 190.0938×10^(4)km^(2),accounting for 20.2%of the total suitable area,this represents a decrease of 63.53%~67.13%compared to the suitable area of Tulipa iliensis under the paleoclimate scenario.Under the Shared Socioeconomic Pathways(SSP)scenarios,in 2050 and 2090,Tulipa iliensis is projected to experience a decrease in the High,Mid,and Low-suitability areas under the SSP126 climate scenario by 7.10%~12.96%,2.96%~4.27%and 4.80%~7.96%,respectively.According to the SSP245 scenario,the high suitability area experienced a slight expansion of 2.26%in 2050,but a reduction of 6.32%in 2090.In the SSP370 scenario,the High-suitability areas had a larger reduction rate of 11.24%in 2050,while the Mid-suitability and Low-suitability areas had smaller expansion rates of 0.36%and 4.86%,respectively.In 2090,the High-suitability area decreased by 4.84%,while the Mid and Low-suitability areas experienced significant expansions of 15.73%and 45.89%,respectively.According to the SSP585 scenario,in the future,the High,Mid,and Low-suitability areas are projected to increase by 5.09%~7.21%,7.57%~17.66%,and 12.30%~48.98%,respectively.The research offers enhanced theoretical direction for preserving Tulipa iliensis’genetic variety amidst evolving climatic scenarios.
基金Project supported by the National Key R&D Program of China(Grant No.2021YFB3500300)the National Natural Science Foundation of China(Grant Nos.51931007and 51871005)+4 种基金the Program of Top Disciplines Construction in Beijing(Grant No.PXM2019014204500031)the International Research Cooperation Seed Fund of Beijing University of Technology(Grant No.2021B23)the Key Program of Science and Technology Development Project of Beijing Municipal Education Commission of China(Grant No.KZ202010005009)General Program of Science and Technology Development Project of Beijing Municipal Education Commission(Grant No.KM202010005009)Chaoyang District Postdoctoral Research Foundation。
文摘Macroscopic magnetic properties of magnets strongly depend on the magnetization process and the microstructure of the magnets.Complex materials such as hard-soft exchange-coupled magnets or just real technical materials with impurities and inhomogeneities exhibit complex magnetization behavior.Here we investigate the effects of size,volume fraction,and surroundings of inhomogeneities on the magnetic properties of an inhomogeneous magnetic material via micromagnetic simulations.The underlying magnetization reversal and coercivity mechanisms are revealed.Three different demagnetization characteristics corresponding to the exchange coupling phase,semi-coupled phase,and decoupled phase are found,depending on the size of inhomogeneities.In addition,the increase in the size of inhomogeneities leads to a transition of the coercivity mechanism from nucleation to pinning.This work could be useful for optimizing the magnetic properties of both exchange-coupled nanomagnets and inhomogeneous single-phase magnets.
基金supported by the Pre-research Fund (N0901-041)the Funding of Jiangsu Innovation Program for Graduate Education(CX09B 081Z CX10B 110Z)
文摘A novel adaptive sampling interval algorithm for multitarget tracking is presented. This algorithm which is based on interacting multiple models incorporates the grey relational grade （GRG） into the particle swarm optimization （PSO）. Firstly, the desired tracking accuracy is set for each target. Secondly, sampling intervals are selected as particles, and then the advantage of the GRG is taken as the measurement function for resource management. Meanwhile, the fitness value of the PSO is used to measure the difference between desired tracking accuracy and estimated tracking accuracy. Finally, it is suggested that the radar should track the target whose prediction value of the next sampling interval is the smallest. Simulations show that the proposed method improves both the tracking accuracy and tracking efficiency of the phased-array radar.
基金supported by the National High Technology Research and Development Program of China(863 Program),No.2012AA020905the Biological Industry Development Funds of Shenzhen,No.JC201005260093A+1 种基金the National Natural Science Foundation of China/Research Grants Council Joint Research Scheme,No.81161160570the National Natural Science Foundation of China,No.81171143the Tsinghua-Yue-Yuen Medical Sciences Fund
文摘Transient brain ischemia has been shown to induce hyperphosphorylation of the micro- tubule-associated protein tau. To further determine the mechanisms underlying these processes, we investigated the interaction between tau, glycogen synthase kinase （GSK）-313 and protein phos- phatase 2A. The results confirmed that tau protein was dephosphorylated during brain ischemia; in addition, the activity of GSK-3β was increased and the activity of protein phosphatase 2A was de- creased. After reperfusion, tau protein was hyperphosphorylated, the activity of GSK-3β was de- creased and the activity of protein phosphatase 2A remained low. Importantly, the interaction of tau with GSK-3β and protein phosphatase 2A was altered during ischemia and reperfusion. Lithium chloride could affect tau phosphorylation by regulating the interaction of tau with GSK-3β and pro- tein phosphatase 2A, and improve learning and memory ability of rats after transient brain ischemia. The present study demonstrated that it was the interaction of tau with GSK-3β and protein phos- phatase 2A, rather than their individual activities, that dominates the phosphorylation of tau in tran- sient brain ischemia. Hyperphosphorylated tau protein may play an important role in the evolution of brain injury in ischemic stroke. The neuroprotective effects of lithium chloride partly depend on the inhibition of tau phosphorylation during transient brain ischemia.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFC1903405)Advanced Subject of Beijing,China(Grant No.PXM2019_014204_500031)
文摘Significant efforts have been put into the recycling of bulk Nd–Fe–B sintered magnet wastes around the world in the past decade because bulk Nd–Fe–B sintered magnet wastes are valuable secondary rare-earth resources.There are two major facts behind the efforts.First, the waste magnets contain total rare-earth content as high as more than 30 wt.%, which is higher than most natural rare-earth mines.Second, the waste magnets maintain the physical and chemical properties of the original magnets even with deterioration of the properties on surfaces due to corrosion and contamination.In this review,various techniques for recycling bulk Nd–Fe–B sintered magnet wastes, the overall properties of the recycled Nd–Fe–B sintered magnets, and the mass production of recycled magnets from the wastes are reviewed.
基金Supported by National Natural Science Foundation of Hainan Province(217157)2017 Provincial College Students' Innovation and Entrepreneurship Training Program(201711100005)2018 Provincial Key Discipline (Thalassochemistry) Construction Fund
文摘[Objectives]This study was conducted to optimize the extraction process of Sipunculus nudus polysaccharide and study the antioxidant activity of S. nudus polysaccharide. [Methods] S. nudus polysaccharide was extracted by ultrasonic microwave assisted method,during which univariate factors including solidliquid ratio,time,temperature,ultrasonic power,microwave power were investigated,to select optimal extracting conditions,which were also verified by an response surface optimization experiment( an four-factor three-level test); and the antioxidant activity of S. nudus polysaccharide was studied by determining its DPPH radical scavenging capacity. [Results]Through univariate factor investigation and response surface optimization test,it was found that the response surface results were consistent with univariate results. The optimized conditions were as follows: solid-liquid ratio at 1∶ 15,ultrasonic temperature at 60 ℃,ultrasonic power of 360 W and microwave power of 200 W,and the predicted polysaccharide extracting amount was 4. 35 mg/g. Under the optimized extracting conditions,the average extracting amount of S. nudus polysaccharide was 4. 38 mg/g,which is close to the theoretical predicted value( 4. 35 mg/g). And the results of this study also showed that different concentrations of polysaccharide solutions have different scavenging effects on DPPH free radical. At the polysaccharide concentration of0. 16 mg/ml,the maximum value of DPPH radical scavenging rate was 7. 22%,indicating that polysaccharide has certain antioxidant capacity. [Conclusions]This method is a new trial with satisfactory results.
基金financially supported by the National High Technology Research and Development Program of China(2012AA063201)the Beijing Municipal Natural Science Foundation(2172012)the State Key Laboratory of Rare Earth Permanent Magnetic Materials Opening Foundation(SKLREPM17OF02).
文摘Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques,it is urgent to develop an efficient recycling technique for leftover sludge from the manufacturing process of neodymium-iron-boron(Nd-Fe-B)sintered magnets.In the present study,centerless grinding sludge from the Nd-Fe-B sintered magnet machining process was selected as the starting material.The sludge was subjected to a reduction-diffusion(RD)process in order to synthesize recycled neodymium magnet(Nd2Fe14B)powder;during this process,most of the valuable elements,including neodymium(Nd),praseodymium(Pr),gadolinium(Gd),dysprosium(Dy),holmium(Ho),and cobalt(Co),were recovered simultaneously.Calcium chloride(CaCl2)powder with a lower melting point was introduced into the RD process to reduce recycling cost and improve recycling efficiency.The mechanism of the reactions was investigated systematically by adjusting the reaction temperature and calcium/sludge weight ratio.It was found that single-phase Nd2Fe14B particles with good crystallinity were obtained when the calcium weight ratio(calcium/sludge)and reaction temperature were 40 wt% and 1050℃,respectively.The recovered Nd2Fe14B particles were blended with 37.7 wt% Nd4Fe14B powder to fabricate Nd-Fe-B sintered magnets with a remanence of 12.1 kG(1 G=1×10^-4T),and a coercivity of 14.6 kOe(1 Oe=79.6A·m^-1),resulting in an energy product of 34.5 MGOe.This recycling route promises a great advantage in recycling efficiency as well as in cost.
基金sponsored by the Basic Science Center Project of National Natural Science Foundation of China(72088101)。
文摘Shallow conductive heterogeneity can lead to static shifts ain the apparent resistivity sounding curve of controlled-source audio-frequency magnetotellurics(CSAMT).The static effect will shift the apparent resistivity curves along with axial log-log coordinates.Such an effect,if not properly processed,can distort the resistivity of rock formation and the depth of interfaces,and even make the geological structures unrecognizable.In this paper,we discuss the reasons and characteristics of the static shift and summarize the previous studies regarding static shift correction.Then,we propose the Guided Image Filtering algorithm to suppress static shifts in CSAMT.In detail,we use the multi-window superposition method to superimpose 1D signals into a 2D matrix image,which is subsequently processed with Guided Image Filtering.In the synthetic model study and field examples,the Guided Image Filtering algorithm has effectively corrected and suppressed static shifts,and finally improved the precision of data interpretation.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFB0701903 and 2016YFA0401502)the National Natural Science Foundation of China(Grant No.12041202)+2 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2017023)the Guangdong Natural Science Foundation,China(Grant No.2016A030313129)the Department of Science and Technology of Guangdong Province under grant project of energy-resolved neutron imaging instrument.
文摘The neutron Bragg-edge imaging is expected to be a new non-destructive energy-resolved neutron imaging technique for quantitatively two-dimensional or three-dimensional visualizing crystallographic information in a bulk material,which could be benefited from pulsed neutron source.Here we build a Bragg-edge imaging system on the General Purpose Powder Diffractometer at the China Spallation Neutron Source.The residual strain mapping of a bent Q235 ferrite steel sample has been achieved with a spectral resolution of 0.15%by the time-of-flight neutron Bragg-edge imaging on this system.The results show its great potential applications in materials science and engineering.
文摘As a new choice for the treatment of degenerative lumbar disease, artificial lumbar disc replacement has been widely used in clinical surgery. The finite element is a very effective method to predict and simulate the surgery effect. The purpose of this paper is to review the applications of finite element in artificial lumbar disc replacement, such as design of artificial lumbar disc prosthesis, risk and effect evaluation of artificial lumbar disc replacement, and assessment of operation methods. Lastly, we discuss the future development of finite element method applied in this field, including personalized design of the prosthesis, postoperative behavior guide, and artificial lumbar disc replacement combined with fusion surgery. In conclusion, as an invaluable complement to biomechanical experiments and clinical studies, the finite element method makes important contributions to our understanding of biomechanics of intervertebral disc, and plays an important role in the field of artificial lumbar disc replacement.
文摘Many researches point out that intervertebral pressure and transformation are key parameters for evaluating intervertebral disc degeneration. Aiming at avoiding the damage caused by direct and indirect measuring methods, this research proposes a cylindroid hypothesis and measuring method, which can monitor the strain condition of the intervertebral disc in vivo and real-time without being damaged.
基金Project supported by the National Natural Science Foundation of China (52201199,52271161)the Program of Top Disciplines Construction in Beijing (PXM2019_014204_500031)。
文摘The synthesis of size-controlled Sm_(2)Fe_(17) magnetic particles is a prerequisite for the fabrication of highperformance Sm_(2)Fe_(17)N_(3) permanent magnetic materials.Here,Sm_(2)Fe_(17) was synthesized using a costeffective reduction-diffusion method.The calcium chloride molten salt was introduced to control the particle size and achieve a single phase of Sm_(2)Fe_(17).The effects of reduction-diffusion reaction temperature and the amount of added calcium chloride on the phase constitution and microstructure of the final product of reduction-diffusion were systematically investigated.Adding an appropriate amount of calcium chloride can effectively inhibit the overgrowth and sintering of the reduced particles.By employing the strategy of adding 20 wt% of calcium chlorides into the green compacts,we were able to successfully synthesize uniform Sm_(2)Fe_(17) particles that are well-dispersed,with an average size of 2.2 μm.Furthermore,by combining the optimal reduction-diffusion conditions and the nitriding process,the hard magnetic Sm_(2)Fe_(17)N_(3) material was successfully obtained.This study could be useful for the development of high-performance Sm_(2)Fe_(17)N_(3) magnetic materials utilizing reduction-diffusion technology.
基金Project supported by the National Key Research and Development Program of China(2021YFB3500300)the National Natural Science Foundation of China(51931007,51871005,52201212,52271161)+1 种基金General Program of Science and Technology Development Project of Beijing Municipal Education Commission of China(KM201710005006)the Program of Top Disciplines Construction in Beijing(PXM2019_014204_500031)。
文摘Due to its large magnetocrystalline anisotropy field and high Curie temperature,SmCo-based magnets are irreplaceable in high-temperature applications,The hot-deformed SmCo-based magnets are especially attractive for their excellent corrosion resistance,making them more suitable for harsh environments.However,it is still challenging for hot-deformed SmCo-based magnets to obtain high magnetization and high coercivity simultaneously.Therefore,it is necessary to analyze the relationship between its microstructure and magnetic properties and explore its magnetic hardening mechanism to guide the further improvement of magnetic properties.In this paper,the anisotropic heterostructure SmCo_(5)magnet was prepared by combining large height-reduction and introducing a nano-grained Smrich phase.Strong c-axis texture,(BH)m of 16.1 MGOe,and H_(ci)of 9.6 kOe were obtained via the heterostructure with SmCo_(5)micron-grain and Sm-rich nano-scale precipitates.The magnetic domain observation and technical magnetization analysis demonstrate that the coe rcivity mechanism is dominated by nucleation.The results also show that the smooth and Sm-rich precipitated grain boundary provides weak pinning effects.It provides a reference for the development of high-pe rformance nanocrystalline SmCo_(5)magnets.
基金This work was financially supported by the National Key R&D Program of China(No.2021YFB3500300)the National Natural Science Foundation of China(Nos.51931007,51871005,and 51801005)+2 种基金the Key Program of Science and Technology Development Project of Beijing Municipal Education Commission of China(No.KZ202010005009)the Chaoyang District Postdoctoral Research Foundation(No.2021ZZ-36)the International Research Cooperation Seed Fund of Beijing University of Technology(No.2021B23).
文摘Nanocomposite permanent magnets have ultra-high theoretical magnetic energy products,due to cou-pling of the soft/hard magnetic phases,inciting strict microstructural requirements.In this study,the microstructure evolution,including the phase transition,morphological changes,and texture formation,of hot-deformed SmCo-based nanocomposites under thermal-stress-strain coupling was characterized to determine a possible strategy for achieving high performance.The SmCo_(5)/α-Fe nanocomposites precursor contained fine and dispersed Sm(Fe,Co)_(5)and Fe-Co grains and exhibited a two-stage phase transforma-tion accompanied by grain growth.In the early stage of deformation at relatively low temperature,the adjacent Sm(Co,Fe)5 and Fe-Co phase formed the Sm_(2)(Co,Fe)_(17)-H phase,which was stable only with small grain sizes.In the high-temperature deformation stage,the Sm_(2)(Co,Fe)_(17)-H phase transformed into the Sm_(2)(Co,Fe)_(17)-R phase with large grain sizes.In addition,the strong c-axis texture formed in the Sm(Co,Fe)_(5)phase but not in the Sm_(2)(Co,Fe)_(17)-R phase.Subsequently,the phase transition process and texture formation mechanism were systematically analyzed by transmission electron microscopy.The ini-tiation of a slip system and/or preferential grain growth explained the formation of texture under the action of uniform stress and strain and assisted by dispersed Sm-rich nanograins.The Sm_(2)(Co,Fe)_(17)-R grains with poor orientations and large grain sizes did not achieve magnetic hardening,which also dam-age the magnetic properties.According to the results of this work,we also presented a new strategy to prepare high-performance SmCo-based nanocomposites magnets.
基金Project supported by the National Key R&D Program of China (2021YFB3500801)the National Natural Science Foundation of China(52271161)+5 种基金the Science and Technology Program of Anhui Province(201903a07020002)General Program of Science and Technology Development Project of Beijing Municipal Education Commission (KM202010005009)"QiHang Programme"for Faculty of Materials and Manufacturing,BJUT (QH202211)Program of Top Disciplines Construction in Beijing (PXM2019_014204_500031)Key Laboratory of Ionic Rare Earth Resources and Environment,Ministry of Natural Resources of the People’s Republic of China (2022IRERE302)the State Key Laboratory of Rare Earth Permanent Magnetic Materials Opening Foundation(SKLREPM170F02)。
文摘In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-selective dissolution washing proc ess.The chemo-selective dissolution effect of various solution(deionized water,dilute acetic acid solution,NH_(4)Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder.The NH_(4)Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase.Besides,the optimal NH_(4)Cl concentration and liquid-to-solid ratio were investigated.As a consequence,the contents of Ca,O,and H after optimal washing process are reduced to 0.07 wt%,0.31 wt% and 0.22 wt%,respectively.Hence,M_(3) Tis increased to 146.72 emu/g,which is 33% higher than that of the initial sludge.Then,the regenerated Nd-Fe-B sintered magnets with properties of B_(r)=11.66 kG,H_(cj)=16.49 kOe,and(BH)_(m)=31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders.Compared with the corresponding regenerated magnets washed with deionized water,the remanence and coercivity are increased by 18% and 59%,respectively.
基金Project supported by the Beijing Municipal Natural Science Foundation(2172012)the International S&T Cooperation Program of China(2015DFG52020)the National High Technology Research and Development Program of China(2012AA063201)
文摘Environmental friendly recycling process for Nd-Fe-B sintered magnet sludges generated in the manufacturing process, which contain large amount of rare earth, including Nd, Pr and Dy, is badly needed so far. In present study, we have developed an effective route to obtain recycled sintered magnets from Nd-Fe-B sintered magnet sludges by calcium reduction-diffusion(RD) process. Compared to conventional recycling process, our research is focused on recovering most of the useful elements, including Nd, Pr, Dy, Co, and Fe together instead of just rare earth elements. To improve the recycling efficiency and reduce pollution, the co-precipitating parameters were simulated and calculated using MATLAB software. Most of useful elements were recovered by a co-precipitation method, and the obtained composite powders were then directly fabricated as recycled Nd-Fe-B powders by a calcium reduction-diffusion(RD) method. The recovery rates are 98%, 99%, 99%, 93%, and 99%, for Nd, Pr, Dy, Co, and Fe, respectively. The amount of useful elements contained in the recovered composite powders is greater than99.71 wt%. The process of RD for synthesizing NdFeB and subsequently removing CaO was thoroughly investigated. Furthermore, the recycled Nd-Fe-B magnet exhibits a remanence of 1.1 T, a coercivity of1053 kA/m, and an energy product of 235.6 kJ/m~3, respectively, indicating that recycled Nd-Fe-B sintered magnet was successfully recovered from the severely contaminated sludges via an effective recycling route.
基金the National Natural Science Foundation of China(51871005,51931007)the International S&T Cooperation Program of China(2015DFG52020)。
文摘The evolution of the microstructure,microchemistry and magnetic properties of the Sm(CobalFe_(0.28)-CuyZrx)_(7.6)magnets with different Zr and Cu contents was investigated.It is found that the coercivity of the Sm(Co,Fe,Cu,Zr)_(z)magnets is sensitive to Zr content.The deficiency of Zr content causes heterogeneity of Cu and Fe distributions,while an excessive Zr content leads to the formation of a SmCoZr impurity phase.The cellular structure and distribution of Cu concentration.gradient between the cell boundary phase and cell pha se are destroyed by inappropriate Zr content,which results in a reduction of coercivity.The Cu concentration difference between the cell boundary phase and cell phase increases with increasing Cu content.The coercivity of the Sm(CobalFe_(0.28)CuyZ_(r0.02))_(7.6)magnets increases from 10.4 to 25.4 kOe for y=0.05 and y=0.07.However,the excess of Cu element destroys the cell boundary phase and enlarges the cell size,resulting in a significant decrease of squareness and energy density.The optimum performance(remanence of 11.4 kG,coercivity of 25.4 kOe,maximum magnetic ene rgy product of 30.4 MGOe)was obtained for the Sm(Co_(0.63)Fe_(0.28)Cu_(0.07)Zr_(0.02))_(7.6)magnet.
基金financially supported by the National Basic Research Program of China(No.2012CB619101)the National Natural Science Foundation of China(No.81271957)the Basic Research Project of Shenzhen,China(No. JCYJ20120616142847342)
文摘Surgical implant-associated bacterial infection is becoming a serious clinical problem. A series of copper-bearing titanium alloy, Ti-6Al-4V-xCu （x = 1, 3, 5 wt%）, were fabricated in the present study in order to reduce the hazard of the bacterial infection problem by means of the strong antibacterial ability of Cu element. The metallography, X-ray diffraction, antibacterial ability, corrosion resistance and cytotoxicity of Ti-6Al-4V-xCu alloys were preliminarily studied with comparison to the commercial medical Ti-6Al-4V alloy. The Ti-6Al- 4V-xCu alloys showed obvious antibacterial abilities with good corrosion resistance and cytocompatibility, and the antibacterial role was enhanced with increasing Cu content, which has significant potential for clinical applications as surgical implant materials.
基金Project supported by the National Natural Science Foundation of China(51931007,51871005,51801005)。
文摘In this article,the Sm_(2)Co_(7)/α-Fe nanocomposite magnets were prepared by high energy ball milling and spark plasma sintering method.The effect of soft phase content on the magnetic properties was studied.Up to 30 wt% α-Fe was added into Sm_(2)Co_(7) matrix without the decrease of remanence.Optimal energy product(BH)max of 9.2 MGOe was obtained with 20 wt% α-Fe.TEM observation shows that the grain size of α-Fe is 20-50 nm which ensures a good coupling effect between soft and hard phase.One more thing needs to be mentioned is that there exists inter-diffusion between Sm-Co phase and α-Fe phase.Moreover,our results can also illustrate that the Sm_(2)Co_(7)/α-Fe nanocomposite magnets are able to acquire better magnetic properties than the SmCo_(5)/α-Fe magnets prepared by the same process due to the large domain width of Sm_(2)Co_(7) phase.
