Effect of extrusion parameters on degradation of magnesium alloys for bioimplant applications:A review

Magnesium alloys,as a new generation temporary biomaterial,deserve the desirable biocompatibility and biodegradability,and also contribute to the repair of the damaged bone tissues.However,they do not possess the required corrosion resistance in human body fluid.Hot mechanical workings,such as extrusion,influence both the mechanical properties and bio-corrosion behavior of magnesium alloys.This review aims to gather information on how the extrusion parameters(extrusion ratio and temperature)influence the bio-corrosion performances of magnesium alloys.Their effects are mainly ascribed to the alteration of extruded alloy microstructure,including final grain size and uniformity of grains,texture,and the size,distribution and volume fraction of the second phases.Dynamic recrystallization and grain refinement during extrusion provide a more homogeneous microstructure and cause the formation of basal texture,resulting in improved strength and corrosion resistance of magnesium alloy.Extrusion temperature and extrusion ratio are reported as the influential factors in the degradation.The reports reveal that the increase in extrusion ratio and/or the reduction in extrusion temperature cause a decrease in the final grain size,leading to intensification of basal texture,in parallel side of the samples with extrusion line,and to lower volume fraction and size of precipitates in magnesium alloys.These all lead to improving the bio-corrosion resistance of the magnesium alloy implants.

面向并行文件系统的性能评估及相对预测模型

基于Lustre文件系统，对并行文件系统的性能评估和性能建模进行了研究．通过对性能因子的调研，进行了一系列性能评估实验，并提出性能相关性模~（PRModel）．在实验评估和PRModel分析中发现，在不同的性能因子之间存在着紧密的性能相关性，为了挖掘并利用这种相关性信息，提出了一种相对性能预测模（RPPModel）来预测不同性能因子条件下的性能．为了验证RPPModel的有效性，设计了大量实验用例．结果表明，预测结果的平均相对误差能够控制在170／o---28％的范围内，易于使用且具有较好的预测准确度．

Cr3轧辊局部堆焊修复工艺研究

Cr3钢是目前广泛使用的轧辊材料,其局部修复有重要意义。研究了不同预热温度和焊后缓冷对Cr3钢轧辊局部堆焊修复质量的影响。通过焊接工艺试验、无损探伤、焊接热模拟试验及金相分析,证明了在Cr3钢轧辊局部修复中,焊接热影响区的最大焊接收缩量ΔL、马氏体含量均随预热温度的下降而增加;在预热温度相同时,ΔL随冷速降低而降低。在350℃保温缓冷即可明显改善Cr3钢组织。通过缓冷可将常规400℃以上的预热温度降低到200℃而保证不裂。

Cr3轧辊局部修复工艺的焊接热模拟分析

利用焊接工艺试验和热模拟试验研究了预热温度和冷速对高碳含量的轧辊材料Cr3钢焊接性的影响。通过金相分析、X射线衍射分析及温度-体积变化关系的分析,研究了预热温度和冷速影响Cr3钢焊接性的机理,确定了Cr3钢在焊接冷速下的组织,得到了冷却速度与焊后组织、加热区最大收缩量和焊接残余应力的关系。研究表明,控制焊接时的冷却速度是保证这类轧辊材料堆焊修复质量的关键。

Organoid intelligence:Integration of organoid technology and artificial intelligence in the new era of in vitro models

Organoid Intelligence ushers in a new era by seamlessly integrating cutting-edge organoid technology with the power of artificial intelligence.Organoids,three-dimensional miniature organ-like structures cultivated from stem cells,offer an unparalleled opportunity to simulate complex human organ systems in vitro.Through the convergence of organoid technology and AI,researchers gain the means to accelerate discoveries and insights across various disciplines.Artificial intelligence algorithms enable the comprehensive analysis of intricate organoid behaviors,intricate cellular interactions,and dynamic responses to stimuli.This synergy empowers the development of predictive models,precise disease simulations,and personalized medicine approaches,revolutionizing our understanding of human development,disease mechanisms,and therapeutic interventions.Organoid Intelligence holds the promise of reshaping how we perceive in vitro modeling,propelling us toward a future where these advanced systems play a pivotal role in biomedical research and drug development.

Long-and short-range orders in 10-component compositionally complex ceramics

Neutron diffraction and total scattering are combined to investigate a series of single-phase 10-component compositionally complexfluorite-based oxides,[(Pr_(0.375)Nd_(0.375)Yb_(0.25))2(Ti_(0.5)Hf_(0.25)Zr_(0.25))_(2)O_(7)]_(1-x)[(DyHoErNb)O_(7)]_(x),denoted as 10CCFBOxNb.A long-range order-disorder transition(ODT)occurs at x=0.81±0.01 from the ordered pyrochlore to disordered defectfluorite.In contrast to ternary oxides,this ODT occurs abruptly without an observable two-phase region;moreover,the phase stability in 10CCFBOs deviates from the well-established criteria for simpler oxides.Rietveld refinements of neutron diffraction patterns suggest that this ODT occurs via the migration of oxygen anions from the position 48f to 8a,with a smallfinal jump at the ODT;however,the 8a oxygen occupancy changes gradually(without an observable discontinuous jump).We further discover diffuse scattering in Nb-rich compositions,which suggests the presence of short-range order.Using small-box modelling,four compositions near ODT(x=0.75,0.8,0.85,and 1)can be betterfitted by C2221 weberite ordering for the local polyhedral structure at nanoscale.Interestingly,10CCFBO_(0.75)Nb and 10CCFBO_(0.8)Nb possess both long-range pyrochlore order and short-range weberite-type order,which can be understood from severe local distortion of the pyrochlore polyhedral structure.Thus,weberite-type short-range order emerges before the ODT,coexisting and interacting with long-range pyrochlore order.After the ODT,the long-range pyrochlore order vanishes but the short-range weberite-type order persists in the long-range disordered defectfluorite structure.Notably,a drop in the thermal conductivity coincides with emergence of the short-range order,instead of the long-range ODT.

A Tree-Based Approach for Efficient and Accurate Conjunction Analysis

Conjunction analysis is the study of possible collisions between objects in space.Conventional conjunction analysis algorithms are geared towards computing the collision probability between any two resident space objects.Currently,there are few heuristic methods available to select which objects should be considered for a detailed collision analysis.A simple all-on-all collision analysis results in an O(N2)procedure,which quickly becomes intractable for large datasets.The main objective of this research work is to preemptively determine which catalogued objects should be considered for a more detailed conjunction analysis,significantly reducing the number of object pairs to be investigated.The heart of the approach lies in the efficient kd-tree algorithm.It has been found that this binary search method significantly reduces computational cost to a tractable complexity of O(N logN).The conventional tree-based search is modified slightly by accounting for probabilistic nearest neighbors via the Hellinger Distance.Finally,the method is extended to account for Non-Gaussian errors via the inclusion of Gaussian Mixture Models.It has been found that the reduced computational complexity of the kd-tree is maintained,while the applicability of the method is extended to uncertain cases.

Development of surrogate-optimization models for a novel transcritical power cycle integrated with a small modular reactor

In recent years,various types of surrogate optimization models have been proposed to reduce the computational time and to improve the emulation accuracy.In this study,by leveraging an ANN surrogate model developed earlier,a comprehensive and efficient optimization algorithm is conceived for the global optimal design of an integrated regenerative methanol transcritical cycle.It combines a unique converging/diverging classifier model into the surrogate model to form a surrogate-based model,which significantly improves the prediction accuracy of the objective function.Six binary classifiers are explored and the multi-layer feed-forward(MLF)neural network classifier is selected.In addition,within the five global optimizers being explored,the basinhopping(BH)and dual-annealing(DA)are selected.The optimal surrogate-based model and global optimizers are then combined to form a unique surrogate-optimizer model.The surrogate-optimizer model is slightly outperformed by the physics-based model in terms of the optimization results,the time consumption of the surrogate-optimizer model during the optimization searching process is 99%less than that of the physicsbased model.As the results,the surrogate-optimizer model is slightly outperformed by the physics-based model in terms of the optimization results,where the Levelized Cost of Energy(LCOE)of the Surrogate-DA and Surrogate-BH models are 77.912 and 78.876$/MWh,respectively,compared to the 77.190$/MWh of the Baseline model with fairly close penalties between them.In the meantime,the time consumption of the surrogate-optimizer model during the optimization searching process is 99%less than that of the physics-based model.

Application of a PCA-DBN-based surrogate model to robust aerodynamic design optimization

An efficient method employing a Principal Component Analysis(PCA)-Deep Belief Network(DBN)-based surrogate model is developed for robust aerodynamic design optimization in this study.In order to reduce the number of design variables for aerodynamic optimizations,the PCA technique is implemented to the geometric parameters obtained by parameterization method.For the purpose of predicting aerodynamic parameters,the DBN model is established with the reduced design variables as input and the aerodynamic parameters as output,and it is trained using the k-step contrastive divergence algorithm.The established PCA-DBN-based surrogate model is validated through predicting lift-to-drag ratios of a set of airfoils,and the results indicate that the PCA-DBN-based surrogate model is reliable and obtains more accurate predictions than three other surrogate models.Then the efficient optimization method is established by embedding the PCA-DBN-based surrogate model into an improved Particle Swarm Optimization(PSO)framework,and applied to the robust aerodynamic design optimizations of Natural Laminar Flow(NLF)airfoil and transonic wing.The optimization results indicate that the PCA-DBN-based surrogate model works very well as a prediction model in the robust optimization processes of both NLF airfoil and transonic wing.By employing the PCA-DBN-based surrogate model,the developed efficient method improves the optimization efficiency obviously.

Degradation of solid oxide electrolysis cells: Phenomena,mechanisms, and emerging mitigation strategies——A review

Solid oxide electrolysis cell(SOEC) is a promising electrochemical device with high efficiency for energy storage and conversion.However,the degradation of SOEC is a significant barrier to commercial viability.In this review paper,the typical degradation phenomena of SOEC are summarized,with great attention into the anodes/oxygen electrodes,including the commonly used and newly developed anode materials.Meanwhile,mechanistic investigations on the electrode/electrolyte interfaces are provided to unveil how the intrinsic factor,oxygen partial pressure pO2,and the electrochemical operation conditions,affect the interracial stability of SOEC.At last,this paper also presents some emerging mitigation strategies to circumvent long-term degradation,which include novel infiltration method,development of new anode materials and engineering of the microstructure.

Design,Fabrication,and Analysis of Flapping and Folding Wing Mechanism for a Robotic Bird

Emulating periodic main wing movement of a bird for generating lift and thrust remains a significant challenge in developing a robotic bird.The sequences of main wing motion are comprised of flapping,folding,bending,and twisting.In this paper,we concentrate on the flapping and folding motion,and design two wing mechanisms based on a 4-bar linkage structure:one is only for Flapping Motion(FM)and the other is for simultaneous Flapping and Folding Motion(FFM)during a wing stroke.We derive relationships between length and angle of links to analyze kinematic characteristics of the mechanisms and conduct an optimization to select the length parameters of links that allow maximization of the flapping angle.We run a simulation to confirm the performance of the optimized parameters by examining physical properties,and fabricate two wing mechanisms accordingly.In particular,the folding motion is achieved without using an additional actuator.Force measurements to investigate a lift profile of each mechanism and their quantitative comparison of the performance of both types confirm the benefits of the folding motion in the perspectives of wing frequency and lift.We expect that our kinematic formulation,design procedures,and comparative measurement results can help develop a wing mechanism to create a truly biomimetic robotic bird.

Laser-induced graphene for bioelectronics and soft actuators

Laser-assisted process can enable facile,mask-free,large-area,inexpensive,customizable,and miniaturized patterning of laser-induced porous graphene(LIG)on versatile carbonaceous substrates(e.g.,polymers,wood,food,textiles)in a programmed manner at ambient conditions.Together with high tailorability of its porosity,morphology,composition,and electrical conductivity,LIG can find wide applications in emerging bioelectronics(e.g.,biophysical and biochemical sensing)and soft robots(e.g.,soft actuators).In this review paper,we first introduce the methods to make LIG on various carbonaceous substrates and then discuss its electrical,mechanical,and antibacterial properties and biocompatibility that are critical for applications in bioelectronics and soft robots.Next,we overview the recent studies of LIG-based biophysical(e.g.,strain,pressure,temperature,hydration,humidity,electrophysiological)sensors and biochemical(e.g.,gases,electrolytes,metabolites,pathogens,nucleic acids,immunology)sensors.The applications of LIG in flexible energy generators and photodetectors are also introduced.In addition,LIG-enabled soft actuators that can respond to chemicals,electricity,and light stimulus are overviewed.Finally,we briefly discuss the future challenges and opportunities of LIG fabrications and applications.

Additive manufacturing of copper-stainless steel hybrid components using laser-aided directed energy deposition

Combining dissimilar materials in a single component is an effective solution to integrate diverse material properties into a single part.Copper-stainless steel hybrid components are attracting more and more attention since the high thermal conductivity of copper can greatly enhance the thermal performance of stainless steel,which benefits its applications in many industries.However,direct joining of copper and stainless steel such as SS316 L is challenging since they preserve significant dissimilarities in physical,chemical,and thermo-mechanical properties.This paper aims to fabricate well-bonded copper-SS316 L hybrid parts using a laser-aided directed energy deposition(DED) process.A nickel-based alloy Deloro22(D22) is introduced between copper and SS316 L to address the detrimental issues in copper-SS316 L direct joints.Using this technique,defect-free interfaces are achieved at both the D22-SS316 L and copper-D22 transition zones.Tensile testing of Cu-D22-SS316 L and D22-SS316 L hybrid parts shows the fracture occurs at pure copper and SS316 L region,respectively,indicating an excellent bonding at the interfaces.Ascending in the building direction,a transition of grain structure is observed.A significant diffusion zone is obtained at both the D22-SS316 L and the Cu-D22 interfaces.The large diffusion distance results in a smooth variation in microhardness over the dissimilar materials.The microhardness increases from SS316 L to D22 with the highest value of 240 HV and then decreases from D22 to Cu with the lowest value of 63 ± 4 HV.Testing of thermophysical properties of the Cu-D22-SS316 L system indicates there is a ~300 % increase in thermal diffusivity and a ~200 % increase in thermal conductivity when compared to pure SS316 L.The significant increase in thermal diffusivity and conductivity validates the enhanced thermal performance of SS316 L when it is joined with pure copper.

4D printing of polyurethane paint-based composites

In recent studies,polyurethane has shown multiple properties that make it an excellent candidate material in 4D printing.In this study,we present a simple and inexpensive additive method to print waterborne polyurethane paint-based composites by adding carboxymethyl cellulose(CMC)and silicon oxide(SiO2)nanoparticles to the paint.The first function of CMC and SiO_(2) is to improve rheological properties of the polyurethane paint for making a printable precursor,which improves the printing resolution and enhances additive manufacturability.Second,the composite precursors improve the curing rate of the polyurethane paint without changing its inherited shape memory properties.Third,the printed composite parts shown enhanced mechanical strength compared with that of the parts printed with pure polyurethane.Finally,the 3D printedpolyurethane-CMCandSiO_(2) parts exhibit time-resolved shape transformation upon heat stimulation.To the best of our knowledge,this is the first study of using the polyurethane paint as the precursor for 4D printing,which would open new possibilities in future applications in biomedical engineering,soft robotics and so on.

Graphene coatings for corrosion resistance of nickel and copper in acidic,alkaline and neutral environments

Graphene coatings have been reported to provide impressive corrosion resistance to nickel(Ni)and copper(Cu),because of remarkable characteristics of inertness and impermeablity of graphene.However,as the earlier investigations have generally been carried out in chloride environment,and it is important to understand the performance of graphene coating also in more aggressive environments such as acids and alkali.This study investigated the electrochemical corrosion behaviour of bare and graphene-coated(by chemical vapour deposition(CVD))Ni and Cu in 0.5 M H_(2)SO_(4),0.1 M NaCl and 0.5 M NaOH solutions.Electrochemical tests and post corrosion characterisation revealed the improvement in the corrosion resistance of Ni due to multilayer graphene coating to be similar in the three solutions,i.e.,the robustness of the barrier property of the multilayer graphene is largely unaffected by the aggressiveness of the corrosive environment.However,the improvement in corrosion resistance of bare Ni due to multilayer graphene is considerably greater(nearly 3 orders of magnitude)in the most aggressive of the test solutions(0.5 M H_(2)SO_(4)).The improvement is considerably less in 0.5 M NaOH because bare Ni develops a robust passive layer in highly alkaline solutions.The improvement in corrosion resistance of bare Cu is limited(within an order of magnitude)in the three solutions because Cu develops only 1-2 layers of graphene.

DSMC modeling of rarefied ionization reactions and applications to hypervelocity spacecraft reentry flows

The DSMC modeling is developed to simulate three-dimensional(3D)rarefied ionization flows and numerically forecast the communication blackout around spacecraft during hypervelocity reentry.A new weighting factor scheme for rare species is introduced,whose key point is to modify the corresponding chemical reaction coefficients involving electrons,meanwhile reproduce the rare species in resultants and preserve/delete common species in reactants according to the weighting factors.The resulting DSMC method is highly efficient in simulating weakly inhomogeneous flows including the Couette shear flow and controlling statistical fluctuation with high resolution.The accurate reliability of the present DSMC modeling is also validated by the comparison with a series of experimental measurements of the Shenzhou reentry capsule tested in a low-density wind tunnel from the HAI of CARDC.The obtained electron number density distribution for the RAM-C II vehicle agrees well with the flight experiment data,while the electron density contours for the Stardust hypervelocity reentry match the reference data completely.In addition,the present 3D DSMC algorithm can capture distribution of the electron,N+and O+number densities better than the axis-symmetric DSMC model.The introduction of rare species weighting factor scheme can significantly improve the smoothness of the number density contours of rare species,especially for that of electron in weak ionization case,while it has negligible effect on the macroscopic flow parameters.The ionization characteristics of the Chinese lunar capsule reentry process are numerically analyzed and forecasted in the rarefied transitional flow regime at the flying altitudes between 80 and 97 km,and the simulations predict communication blackout altitudes which are in good agreement with the actual reentry flight data.For the spacecraft reentry with hypervelocity larger than the second cosmic speed,it is forecasted and verified by the present DSMC modeling that ionization reactions will cover the windward capsule surface,leading to reentry communication blackout,and the communication interruption must be considered in the communication design during reentry in rarefied flow regimes.

Review of onsite temperature and solar forecasting models to enable better building design and operations

Advanced building controls and energy optimization for new constructions and retrofits rely on accurate weather data.Traditionally,most studies utilize airport weather information as the decision inputs.However,most buildings are in environments that are quite different than those at the airport miles away.Tree cover,adjacent buildings,and micro-climate effects caused by the larger surrounding area can all yield deviations in air temperature,humidity,solar irradiance,and wind that are large enough to influence design and operation decisions.In order to overcome this challenge,there are many prior studies on developing weather forecasting algorithms from micro-to meso-scales.This paper reviews and complies knowledge on common weather data resources,data processing methodologies and forecasting techniques of weather information.Commonly used statistical,machine learning and physical-based models are discussed and presented as two major categories:deterministic forecasting and probabilistic forecasting.Finally,evaluation metrics for forecasting errors are listed and discussed.

Sperm quality metrics were improved by a biomimetic microfluidic selection platform compared to swim-up methods

Sperm selection is an essential component of all assisted reproductive treatments(ARTs)and is by far the most neglected step in the ART workflow in regard to technological innovation.Conventional sperm selection methodologies typically produce a higher total number of sperm with variable motilities,morphologies,and levels of DNA integrity.Gold-standard techniques,including density gradient centrifugation(DGC)and swim-up(SU),have been shown to induce DNA fragmentation through introducing reactive oxygen species(ROS)during centrifugation.Here,we demonstrate a 3D printed,biologically inspired microfluidic sperm selection device(MSSP)that utilizes multiple methods to simulate a sperms journey toward selection.Sperm are first selected based on their motility and boundary-following behavior and then on their expression of apoptotic markers,yielding over 68%more motile sperm than that of previously reported methods with a lower incidence of DNA fragmentation and apoptosis.Sperm from the MsSP also demonstrated higher motile sperm recovery after cryopreservation than that of sU or neat semen.Experiments were conducted side-by-side against conventional SU methods using human semen(n=33)and showed over an 85%improvement in DNA integrity with an average 90%reduction in sperm apoptosis.These results that the platform is easy-to-use for sperm selection and mimics the biological function of the female reproductive tract during conception.

A Model of High-Speed Endovascular Sonothrombolysis with Vortex Ultrasound-Induced Shear Stress to Treat Cerebral Venous Sinus Thrombosis

This research aims to demonstrate a novel vortex ultrasound enabled endovascular thrombolysis method designed for treating cerebral venous sinus thrombosis(CVST).This is a topic of substantial importance since current treatment modalities for CVST still fail in as many as 20%to 40%of the cases,and the incidence of CvST has increased since the outbreak of the coronavirus disease 2019 pandemic.Compared with conventional anticoagulant or thrombolytic drugs,sonothrombolysis has the potential to remarkably shorten the required treatment time owing to the direct clot targeting with acoustic waves.However,previously reported strategies for sonothrombolysis have not demonstrated clinically meaningful outcomes(e.g.,recanalization within 30 min)in treating large,completely occluded veins or arteries.Here,we demonstrated a new vortex ultrasound technique for endovascular sonothrombolysis utilizing wavematter interaction-induced shear stress to enhance the lytic rate substantially.Our in vitro experiment showed that the lytic rate was increased by at least 64.3%compared with the nonvortex endovascular ultrasound treatment.A 3.1-g,7.5-cm-long,completely occluded in vitro 3-dimensional model of acute CVST was fully recanalized within 8 min with a record-high lytic rate of 237.5 mg/min for acute bovine clot invitro.Furthermore,we confirmed that the vortex ultrasound causes no vessel wall damage over ex vivo canine veins.This vortex ultrasound thrombolysis technique potentially presents a new life-saving tool for severe CVST cases that cannot be efficaciously treated using existing therapies.

Nanodroplet-mediated catheter-directed sonothrombolysis of retracted blood clots

One major challenge in current microbubble(MB)and tissue plasminogen activator(tPA)-mediated sonothrombolysis techniques is effectively treating retracted blood clots,owing to the high density and low porosity of retracted clots.Nanodroplets(NDs)have the potential to enhance retracted clot lysis owing to their small size and ability to penetrate into retracted clots to enhance drug delivery.For the first time,we demonstrate that a sub-megahertz,forwardviewing intravascular(FVI)transducer can be used for ND-mediated sonothrombolysis,in vitro.In this study,we determined the minimum peak negative pressure to induce cavitation with low-boiling point phase change nanodroplets and clot lysis.We then compared nanodroplet mediated sonothrombolysis to MB and tPA mediate techniques.The clot lysis as a percent mass decrease in retracted clots was 9±8%,9±5%,16±5%,14±9%,17±9%,30±8%,and 40±9%for the control group,tPA alone,tPA+US,MB+US,MB+tPA+US,ND+US,and ND+tPA+US groups,respectively.In retracted blood clots,combined ND-and tPA-mediated sonothrombolysis was able to significantly enhance retracted clot lysis compared with traditional MB and tPA-mediated sonothrombolysis techniques.Combined nanodroplet with tPA-mediated sonothrombolysis may provide a feasible strategy for safely treating retracted clots.