摘要：Currently,osteochondral(OC)tissue engineering has become a potential treatment strategy in repairing chondral lesions and early osteoarthritis due to the limited self-healing ability of ***,it is still challenging to ensure the integrity,physiological function and regeneration ability of stratified OC scaffolds in clinical *** OC scaffolds are attractive to overcome the above problems because of their similar biological and mechanical properties with native OC *** a consequence,the researches on biomimetic design to achieve the tissue function of each layer,and additive manufacture(AM)to accomplish composition switch and ultrastructure of personalized OC scaffolds have made a remarkable *** this review,the design methods of biomaterial and structure as well as computer-aided design,and performance prediction of biopolymer-based OC scaffolds are presented;then,the characteristics and limitations of AM technologies and the integrated manufacture schemes in OC tissue engineering are summarized;finally,the novel biomaterials and techniques and the inevitable trends of multifunctional bio-manufacturing system are discussed for further optimizing production of tissue engineering OC scaffolds.

摘要：In this paper, a method to design bird-strike-resistant aircraft structures is presented and illustrated through examples. The focus is on bird strike experiments and simulations. The explicit finite element software PAM-CRASH is employed to conduct bird strike simulations, and a coupled Smooth Particles Hydrodynamic（SPH） and Finite Element（FE） method is used to simulate the interaction between a bird and a target structure. The SPH method is explained, and an SPH bird model is established. Constitutive models for various structural materials, such as aluminum alloys, composite materials, honeycomb, and foam materials that are used in aircraft structures,are presented, and model parameters are identified by conducting various material tests. Good agreements between simulation results and experimental data suggest that the numerical model is capable of predicting the dynamic responses of various aircraft structures under a bird strike,and numerical simulation can be used as a tool to design bird-strike-resistant aircraft structures.

摘要：Orthopedic bone plates are most commonly used for bone fracture fixation for more than 100 *** bone plate design had evolved over time overcoming many challenges such as insufficient strength and excessive plate–bone contact affecting the blood ***,it is only made of two materials,either stainless steel(AISI 316L)or titanium(Ti–6Al–4V).There are two main limitations of metallic bone implants,namely stress shielding and the problem of malocclusion caused by the displacement of the fracture site during *** overcome the two problems,a new bone plate design with the incorporation of auxetic structures is proposed in this *** study aims to use auxetic structure section in the bone plate that would decrease the stiffness of the region,thereby mitigating the stress-shielding effect and at the same time act as a deformable section to enable intra-operative bending for effective alignment while having enough bending strength and *** different auxetic structures namely re-entrant honeycomb and missing rib structures were *** auxetic structure incorporated bone plates were designed,finite element analysis was done,fabricated using direct metal laser sintering technique,and *** results indicate that the re-entrant honeycomb structure incorporated bone plates serve as an effective bone design compared to the conventional bone plate design,in terms of stress shielding and intra-operative bending while offering similar mechanical and bending strength.

摘要：This study investigates the redesign of a structural system with the matrix modification. The inertia congruence transformation is adopted to find the latent roots of a dynamic stiffness matrix, and a method for determining its eigenvalue is proposed. The characteristics of the latent vector for a known latent root and a method for computing it are studied. The mode shapes of the redesigned structure must be differently handled based on whether the structure exhibits persistent or non-persistent natural frequencies.

摘要：A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is *** assumes that the motion of all clutch components can be expressed by a model of epicyclic *** takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races,and it can be used for optimization of design and comparison with other types of sprag clutches.A good deal of analysis shows that the parameters of the steady windup angle,the steady contact force,the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race,while the parameters of the maximum transient windup angle,the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of *** is also shown that the strut angle has great influence on the dynamic engagement performance of *** parameters of the steady windup angle,the maximum transient windup angle,the steady engaging time,the steady contact force,the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle,while the natural frequency of the system increases linearly with the inner strut angle.

摘要：Solar energy has promising potential for building sustainable *** of solar energy into solar fuels plays a crucial role in overcoming the intennittent nature of the renewable energy source.A pliotoclectrochernical (PEC) cell that employs semiconductor as photoelectrode to split water into hydrogen or fixing carbon dioxide (CO2) into hydrocarbon fuels provides great potential to achieve zcrocarbon-oiiiission society.A proper design of those semiconductor photoelectrodes thus directly influences the performance of the PEC *** this review,we investigate the strategics that have been put towards the design of efficiont photoelectrodes for PEC water splitting and CO2 reduction in recent years and provide sonic future design directions toward noxt-goneration FEC cells for water splitting and CO2 reduction.

摘要：Elastic diodes with nonreciprocity have the potential to enable unidirectional modulation of elastic ***,it is a challenge to achieve nonreciprocity at low frequencies(<100 Hz)using existing elastic *** paper proposes a quasizero-stiffness(QZS)elastic diode to resolve such a tough issue and fulfill high-quality low-frequency *** proposed elastic diode is invented by combining a QZS locally resonant metamaterial with a linear one,where the beneficial nonlinearity of the QZS metamaterial facilitates opening an amplitude-dependent band gap at very low ***,the dispersion relation of the QZS metamaterial is derived theoretically based on the harmonic balance method(HBM).Then,the transmissibility of the QZS elastic diode in both the forward and backward directions is calculated through theoretical analyses and numerical ***,the influences of system parameters on the low-frequency nonreciprocal effect are *** results indicate that considerable nonreciprocity is observed at a quite low frequency(e.g.,9 Hz),which is achieved by amplitude-dependent local resonance combined with interface ***,a machine learning-based design optimization is introduced to evaluate and enhance the nonreciprocal effect of the QZS elastic *** the aid of machine learning(ML),the computational cost of predicting nonreciprocal effects during design optimization can be significantly *** design optimization,the nonreciprocal frequency bandwidth can be broadened while maintaining considerable isolation quality at low frequencies.

摘要：In a centrifugal compressor, the leakage flow through the tip clearance generates the tip leakage vortex by the in- teraction with the main flow, and consequently makes the flow in the impeller passage more complex by the inte- raction with the passage vortex. In addition, the tip leakage vortex interacts with the shock wave on the suction surface near the blade tip in the transonic centrifugal compressor impeller. Therefore, the detailed examination for the influence of the tip leakage vortex becomes seriously important to improve the aerodynamic performance cs- pccia｜ly for the transonic centrifugal compressor. In this study, the flows in the transonic centrifugal compressor with and without the tip clearance at the design condition were analyzed numerically by using the commercial CFD code. The computed results revealed that the tip leakage vortex induced by the high loading at the blade tip around the leading edge affected the loss generation by the reduction or the suppression of the shock wave on the suction surface of the blade.

摘要：Mimicking the natural design motifs of structural biological materials is a promising approach to achieve a unique combination of strength and toughness for engineering *** this study,we proposed a 2D computational model,which is a two-hierarchy hybrid composite inspired by the ultrastructural features of *** model is composed of alternating parallel array of two subunits(A&B)mimicking‘mineralized collagen fibril’and‘extrafibrillar matrix’of bone at ultrastructural *** subunit-A is formed by short stiff platelets embedded within a soft *** subunit-B consists of randomly distributed stiff grains bonded by a thin layer of tough adhesive *** assess the performance of the bioinspired design,a conventional unidirectional long-fiber composite made with the same amount of hard and soft phases was *** finite element simulation results indicated that the toughness,strength and elastic modulus of the bioinspired composite was 312%,83%,and 55%of that of the conventional composite,*** toughness improvement was attributed to the prevalent energy-dissipating damage of adhesive phase in subunit-B and crack-bridging by subunit-A,the two major toughening mechanisms in the *** study exemplifies some insights into natural design of materials to gain better material performance.

摘要：The aim of this study is to use a new configuration of porous media in a heat exchanger in continuous hydrothermal flow synthesis(CHFS)system to enhance the heat transfer and minimize the required length of the heat *** this purpose,numerous numerical simulations are performed to investigate performance of the system with porous ***,the numerical simulation for the heat exchanger in CHFS system is validated by experimental ***,porous media is added to the system and six different thicknesses for the porous media are examined to obtain the optimum thickness,based on the minimum required length of the heat ***,by changing the flow rate and inlet temperature of the product as well as the cooling water flow rate,the minimum required length of the heat exchanger with porous media for various inlet conditions is *** investigations indicate that using porous media with the proper thickness in the heat exchanger increases the cooling rate of the product by almost 40% and reduces the required length of the heat exchanger by approximately 35%.The results also illustrate that the most proper thickness of the porous media is approximately equal to 90% of the product tube's *** of this study lead to design a porous heat exchanger in CHFS system for various inlet conditions.