Valorization of Camellia oleifera oil processing byproducts to value-added chemicals and biobased materials: A critical review

The C.oleifera oil processing industry generates large amounts of solid wastes,including C.oleifera shell(COS)and C.oleifera cake(COC).Distinct from generally acknowledged lignocellulosic biomass(corn stover,bamboo,birch,etc.),Camellia wastes contain diverse bioactive substances in addition to the abundant lignocellulosic components,and thus,the biorefinery utilization of C.oleifera processing byproducts involves complicated processing technologies.This reviewfirst summarizes various technologies for extracting and converting the main components in C.oleifera oil processing byproducts into value-added chemicals and biobased materials,as well as their potential applications.Microwave,ultrasound,and Soxhlet extractions are compared for the extraction of functional bioactive components(tannin,flavonoid,saponin,etc.),while solvothermal conversion and pyrolysis are discussed for the conversion of lignocellulosic components into value-added chemicals.The application areas of these chemicals according to their properties are introduced in detail,including utilizing antioxidant and anti-in-flammatory properties of the bioactive substances for the specific application,as well as drop-in chemicals for the substitution of unrenewable fossil fuel-derived products.In addition to chemical production,biochar fabricated from COS and its applications in thefields of adsorption,supercapacitor,soil remediation and wood composites are comprehensively reviewed and discussed.Finally,based on the compositions and structural characteristics of C.oleifera byproducts,the development of full-component valorization strategies and the expansion of the appli-cationfields are proposed.

Effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy

The effect of particle size distribution on the microstructure,texture,and mechanical properties of Al–Mg–Si–Cu alloy was investigated on the basis of the mechanical properties,microstructure,and texture of the alloy.The results show that the particle size distribution influences the microstructure and the final mechanical properties but only slightly influences the recrystallization texture.After the pre-aging treatment and natural aging treatment(T4 P treatment),in contrast to the sheet with a uniform particle size distribution,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids exhibits higher strength and a somewhat lower plastic strain ratio(r) and strain hardening exponent(n).After solution treatment,the sheet with a bimodal particle size distribution of large constituent particles and small dispersoids possesses a finer and slightly elongated grain structure compared with the sheet with a uniform particle size distribution.Additionally,they possess almost identical weak recrystallization textures,and their textures are dominated by CubeND {001}<310> and P {011}<122> orientations.

A review on stress determination and control in metal-based additive manufacturing

Metal additive manufacturing(MAM)is an emerging and disruptive technology that builds three-dimensional(3D)components by adding layer-upon-layer of metallic materials.The complex cyclic thermal history and highly localized energy can produce large temperature gradients,which will,in turn,lead to compressive and tensile stress during the MAM process and eventually result in residual stress.Being an issue of great concern,residual stress,which can cause distortion,delamination,cracking,etc.,is considered a key mechanical quantity that affects the manufacturing quality and service performance of MAM parts.In this review paper,the ongoing work in the field of residual stress determination and control for MAM is described with a particular emphasis on the experimental measurement/control methods and numerical models.We also provide insight on what still requires to be achieved and the research opportunities and challenges.

Dynamic coupled thermo-hydro-mechanical problem for heterogeneous deep-sea sediments under vibration of mining vehicle

Due to the influence of deep-sea environment,deep-sea sediments are usually heterogeneous,and their moduli of elasticity and density change as depth changes.Combined with the characteristics of deep-sea sediments,the thermo-hydro-mechanical coupling dynamic response model of heterogeneous saturated porous sediments can be established to study the influence of elastic modulus,density,frequency,and load amplitude changes on the model.Based on the Green-Lindsay generalized thermoelasticity theory and Darcy’s law,the thermo-hydro-mechanical coupled dynamic response model and governing equations of heterogeneous deep-sea sediments with nonlinear elastic modulus and density are established.The analytical solutions of dimensionless vertical displacement,vertical stress,excess pore water pressure,and temperature are obtained by means of normal modal analysis,which are depicted graphically.The results show that the changes of elastic modulus and density have few effects on vertical displacement,vertical stress,and temperature,but have great effects on excess pore water pressure.When the mining machine vibrates,the heterogeneity of deep-sea sediments has great influence on vertical displacement,vertical stress,and excess pore water pressure,but has few effects on temperature.In addition,the vertical displacement,vertical stress,and excess pore water pressure of heterogeneous deep-sea sediments change more gently.The variation trends of physical quantities for heterogeneous and homogeneous deep-sea sediments with frequency and load amplitude are basically the same.The results can provide theoretical guidance for deep-sea mining engineering construction.

镍/钼复合中间层钎焊连接C/C复合材料和304不锈钢

本文使用在BNi-2或AgCuTi箔片钎料中添加金属中间层(Ni、Mo或Ni/Mo)的方法有效提高了C/C复合材料和304不锈钢真空钎焊接头的强度,并先后对接头的微观结构、连接机理和力学性能进行分析。分析表明,BNi-2+Ni/Mo接头的微观结构包括Cr_(3)C_(2)、Ni(s,s)、Cr_xNi_(y)+MoNi_(4)、MoNi_(4)+Cr_(x)M_(y)和Ni(s,s)+Cr-Fe;AgCuTi+Ni/Mo接头的界面则由TiC、Ag(s,s)+Cu(s,s)、Ni、Ag(s,s)+Cu(s,s)+MoTi、Mo和MoTi+Cu(s,s)+Ag(s,s)构成。有限元模拟结果表明,AgCuTi钎料加持下的镍/钼复合中间层能够有效缓解C/C母材与焊缝界面间的残余应力。室温下BNi-2+Ni/Mo、AgCuTi+Ni、AgCuTi+Mo和AgCuTi+Ni/Mo钎焊接头的平均剪切强度分别为2.57 MPa、10.91 MPa、23.81 MPa和26.77 MPa,有效验证了有限元结果的可靠性。

Stress-corrosion coupled damage localization induced by secondary phases in bio-degradable Mg alloys:phase-field modeling

In this study,a phase-field scheme that rigorously obeys conservation laws and irreversible thermodynamics is developed for modeling stress-corrosion coupled damage(SCCD).The coupling constitutive relationships of the deformation,phase-field damage,mass transfer,and electrostatic field are derived from the entropy inequality.The SCCD localization induced by secondary phases in Mg is numerically simulated using the implicit iterative algorithm of the self-defined finite elements.The quantitative evaluation of the SCCD of a C-ring is in good agreement with the experimental results.To capture the damage localization,a micro-galvanic corrosion domain is defined,and the buffering effect on charge migration is explored.Three cases are investigated to reveal the effect of localization on corrosion acceleration and provide guidance for the design for resistance to SCCD at the crystal scale.

Generation Mechanism of Interfacial Layer and Its Effect on Fe-Cr-Ni/Al-Si-Cu-Ni-Mg Composite Performance

Fe-Cr-Ni/Al-Si-Cu-Ni-Mg composite was taken as the experimental material. The chemical composition of interfacial layer was tested. The generation mechanism and influence of interfacial layer on the composite were analyzed. The results indicated that the generation of interfacial layer is sensitive to temperature. Interfacial layer will generate rapidly when temperature reaches 500 ℃ or above. The interfacial layer is mainly composed of Al, Si, Cu, Fe, and Cr, element Ni distributes at the outward of the interfacial layer for the precipitate of Ni later than Si and Cu, and there is almost no diffusion of Ni during the solution treatment. During heat treatment process, unequal quantity changing of metal atom results in disperse or concentrated vacancies or holes near the matrix. The existence of interfacial layer will induce a decrease of compression strength and plasticity at room temperature and an increase of strength at higher temperature comparing with composite without interfacial layer.

Fabrication and characterization of 3D printed biocomposite scaffolds based on PCL and zirconia nanoparticles

The application of three-dimensional printed polymer scaffolds in repairing bone defects is a promising strategy.Among them,polycaprolactone(PCL)scaffolds are widely studied due to their good processability and controlled degradation rate.However,as an alternative graft for repairing bone defects,PCL materials have poor hydrophilicity,which is not conducive to cell adhesion and growth.In addition,the poor mechanical properties of PCL materials cannot meet the strength required to repair bone defects.In this paper,nano-zirconium dioxide(ZrO2)powder is embedded in PCL material through a meltmixing process,and a regular grid scaffold is constructed by 3D printing.The embedding of nanometer zirconium dioxide powder improves the hydrophilicity and water absorption of the composite scaffold,which is conducive to cell adhesion,proliferation and growth and is beneficial to the exchange of nutrients.Therefore,the PCL/ZrO2 composite scaffold showed better biological activity in vitro.At the same time,the PCL/ZrO2 composite material system significantly improves the mechanical properties of the scaffold.Among them,compared with the pure PCL scaffold,the Young’s modulus is increased by about 0.4 times,and the compressive strength is increased by about 0.5 times.In addition,the osteogenic differentiation results also showed that the PCL/ZrO2 composite scaffold group showed better ALP activity and more effective bone mineralization than the pure PCL group.We believe that the 3D printed PCL/ZrO2 composite scaffold has certain application prospects in repairing bone defects.

Design and Experiment of Non-circular Combined Gear Train Beating-up Mechanism

The most important performance of a beating-up mechanism is that the dwelling time of the sley must ensure the completion of the weft insertion. To meet this requirement, a new non-circular combined gear train beating-up mechanism which is composed of two-stage planetary gear trains is proposed. The first-stage is a Fourier planetary gear train and the second-stage is a non-circular planetary gear train. For designing of this new mechanism, the ideal kinematic equations of the sley are constructed first. Then the kinematic model of the first-stage Fourier planetary gear train is established and the reverse solution for the pitch curves of the second-stage non-circular gears is deduced. With a computer-aided design program, the influences of several important parameters on the pitch curves of the second-stage non-circular gears are analyzed, and a set of preferable structural parameters are obtained. Finally, a test bed of this mechanism is developed and the experimental results show that this new beating-up mechanism can achieve the designed dwelling time, namely it can meet the requirements of beating-up process.

Modeling and Simulation of Adaptive Surface Tracked Vehicle Based on RecurDyn

In order to improve the adaptability of the tracked vehicle in the road and strengthen the grip of the tracked vehicle, a track surface adaptive mechanism was provided. In theory, it has been proved practically. Meanwhile, RecurDyn, which is a multi-body kinematics software, was used to build a multi-body soft hybrid model, based on structure, elasticity, linear damping adaptive tracked vehicle;meanwhile the model was used to carry on the kinematics simulation. Through the comparison between simulated motion trail and that of traditional motion trail, this paper analyzed the deviation of the motion trail and also simulated the motion trail of the warped surface so as to test the adaptive ability of the mechanism. According to the results, the adaptive mechanism was equipped with great surface adaptability. It can also adapt to the complex warped surface, and enjoy a damping effect.

Modelling and control of a spatial dynamic cable

We study the problem of dynamically controlling the shape of a cable that is fixed at one end and attached to an actuated robot at another end. This problem is relevant to unmanned aerial vehicles (UAVs) tethered to a base. While rotorcrafts, such as quadcopters, are agile and versatile in their applications and have been widely used in scientific, industrial and military applications, one of the biggest challenges with such UAVs is their limited battery life that make the flight time for a typical UAVs limited to twenty to thirty minutes for most practical purposes. A solution to this problem lies in the use of cables that tether the UAV to a power outlet for constant power supply. However, the cable needs to be controlled effectively in order to avoid obstacles or other UAVs. In this paper, we develop methods for controlling the shape of a cable using actuation at one end. We propose a discrete model for the spatial cable and derive the equations governing the cable dynamics for both force controlled system and position controlled system. We design a controller to control the shape of the cable to attain the desired shape and perform simulations under different conditions. Finally, we propose a quasi-static model for the spatial cable and discuss the stability of this system and the proposed controller.

RELIABILITY OF TEST LANDS TARGETING IN BED-OF-NAILS STYLE TEST FIXTURE

为在严峻的设备放评价的好沥青印刷电路董事会(聚氯联苯) 的一个系统、精确、柔韧的评估方法被开发。指向可靠性 ofbed-of-nails 测试者被 2D 模式变换成功地评估。探查偏移量向量 withits Weibull 和 Gaussian 分发估计根据批关于错误排列的膜使用为进一步的调查被获得为印刷电路板的一样的类型的测试。

Interaction between bending and mobile charges in a piezoelectric semiconductor bimorph

We study the bending of a two-layer piezoelectric semiconductor plate(bimorph).The macroscopic theory of piezoelectric semiconductors is employed.A set of two-dimensional plate equations is derived from the three-dimensional equations.The plate equations exhibit direct couplings among bending,electric polarization along the plate thickness,and mobile charges.In the case of pure bending,a combination of physical and geometric parameters is identified which characterizes the strength of the interaction between the mechanical load and the distribution of mobile charges.In the bending of a rectangular plate under a distributed transverse mechanical load,it is shown that mobile charge distributions and potential barriers/wells develop in the plate.When the mechanical load is local and self-balanced,the induced carrier distributions and potential barriers/wells are also localized near the loading area.The results are fundamentally useful for mechanically manipulating mobile charges in piezoelectric semiconductor devices.

Optimal patching locations and orientations for maximum energy harvesting efficiency of ultrathin flexible piezoelectric devices mounted on heart surface

Flexible piezoelectric energy harvesters(PEHs)have gained lots of attention in recent years,because of their potential biomechanical applications,such as powering implantable devices.Several in vivo animal experiments have demonstrated that the output power of a flexible PEH varies remarkably with patching orientations and locations,but the underlying mechanism remains unclear yet.Herein,an electromechanical model for a flexible PEH installed on a beating heart is proposed,and a concise relationship between the output power of the device and myocardium strain is established.The results demonstrate that the patching orientations have a significant impact on the output power of the PEH,and the optimal patching orientations for all patching locations are approximately 15–20 degree for PEHs mounted on the left ventricle.The simple theoretical method provided here would be universally effective for choosing the optimal patching locations and orientations of flexible PEHs installed on a nonhomogeneous deformed surface.

Zeolitic imidazolate framework-8 modified poly(vinylidene fluoride-cohexafluoropropylene)/polyacrylonitrile composite separators for Li-ion batteries

As one of the most stable metal-organtic framework(MOF),zeolitic imidazolate framework-8(ZIF-8)has been widely studied for applications in the field of energy storage,catalysis,and environment protection.In this paper,ZIF-8 was employed to enhance the electrochemical properties and thermal stability of the electrospun poly(vinylidene fluoride-co-hexafluoropropylene)/polyacrylonitrile(PVDF-HFP/PAN)composite separator.The results indicate that the test cells assembled with the composite separators show improved rate capability,high discharge capacity,and stable cycling performances.The addition of ZIF-8 can improve the affinity of PVDF-HFP/PAN toward liquid electrolytes,and further enhance the ionic conductivity of the composite separators.In addition,the thermal stability of the PVDF-HFP/PAN separator has been improved by ZIF-8 nanoparticles.This work can provide insight into the application of MOF materials in Li-ion batteries.

全球海啸相关研究进展综述

With the advancement of the global economy,the coastal region has become heavily developed and densely populated and suffers significant damage potential considering various natural disasters,including tsunamis,as indicated by several catastrophic tsunami disasters in the 21st century.This study reviews the up-to-date tsunami research from two different viewpoints:tsunamis caused by different generation mechanisms and tsunami research applying different research approaches.For the first issue,earthquake-induced,landslide-induced,volcano eruption-induced,and meteorological tsunamis are individually reviewed,and the characteristics of each tsunami research are specified.Regarding the second issue,tsunami research using post-tsunami field surveys,numerical simulations,and laboratory experiments are discussed individually.Research outcomes from each approach are then summarized.With the extending and deepening of the understanding of tsunamis and their inherent physical insights,highly effective and precise tsunami early warning systems and countermeasures are expected for the relevant disaster protection and mitigation efforts in the coastal region.

Research Progress of Tung Oil/UV Photocomposite Curing Material

Tung oil(TO)/ultraviolet(UV)photo-composite curing material possesses the characteristics of low curing temperature,low material shrinkage and low environmental pollution.Accordingly,this material must be developed and utilized with the conjugated double bonds contained in the long chain of the main structure(α-tung acid)molecules in the refined TO.The aforementioned material can be chemically modified using a variety of chemical methods to develop a new TO-based UV photocurable material due to its unique chemical properties.This work reviews the research progress of TO/UV photo-composite curing materials in recent years.Firstly,the chemical structure and application of TO and UV Photocatalysis Technology were briefly introduced.Secondly,the research status of novel TO/UV photo-composite curing materials developed by the Diels-Alder reaction was discussed.The method and curing effect of the UVcuring system constructed by other chemically modified TO were also discussed.Thereafter,the application of TO in industrial production is introduced from four directions:the application of TO in biodiesel,the application in synthetic resin,the application in self-healing coating and microcapsules and other applications.Finally,the research and application prospects of TO/UV photo-composite curing materials were presented.

Numerical Analysis of the Hydrodynamic Behavior of a Remotely Operated Vehicle in Multi-Directional Flow

In recent years,Remotely Operated Vehicles(ROVs)have played an increasingly important role in the construc-tion and monitoring of underwater pile foundations.However,due to the open frame structure of such vehicles,a gap of knowledge still exists with regard to their hydrodynamic behavior.In this study,the hydrodynamic stability of such vehicles is investigated numerically by means of a multiple reference frame method.The hydrodynamic characteristics of the ROV when it moves horizontally and upward in the vertical plane are examined.It is found that there is interference between the horizontal and vertical thrusters of the ROV.There is also interference between the propeller thrust and drag(or lift).The effect of the vertical thrusters can increase the horizontal thrust by about 5%.The horizontal thrusters create a low-pressure area below the body,which can make vertical drag experienced by the ROV significantly higher.

Effect of grain boundary diffusion of terbium on mode of mechanical fracture of sintered NdFeB magnets

Grain boundary diffusion process(GBDP)is a widely used method of increasing the coercivity of sintered NdFeB magnets.In this study,the effects of the GBDP on the bending strength and microhardness of sintered NdFeB magnets and the fracture mode were investigated.Results show that the bending strength of magnets is reduced by pickling and heat treatment and greatly recove rs after heavy rare earth element(Tb)grain boundary diffusion.The pickling and the heat treatment cause a slight decrease in microhardness.Compared with the recovery of the bending strength,the hardness decreases after the GBDP.The fracture mode of bended magnets changes from intergranular to transgranular.This study helps in further improving the mechanical and magnetic properties of sintered NdFeB magnets.