Review of: "Graphene molecular nanomemories show unique electronic properties, and their small dimensions, structural strength, and high performance make them a charge storage medium for Nano memory applications"

Review of: "Graphene molecular nanomemories show unique electronic properties, and its small dimensions, structural strength, and high performance make it very promising as a charge storage medium for nanomemory applications"

Review of: "Graphene molecular nanomemories show unique electronic properties, and its small dimensions, structural strength, and high performance make it very promising as a charge storage medium for nanomemory applications"

On the premise of ensuring the structural strength and safety performance of escalator truss, in order to improve the efficiency of design and development of serial escalator truss, a parametric finite element analysis platform for escalator truss is developed by using the secondary development of finite element method and Visual C++ and data interface technology. In this paper, the structural design and strength characteristics of escalator truss with different parameters are studied, and the strength characteristics of escalator truss with maximum boundary load are analysed. The results show that by using the parameterized finite element analysis platform of escalator, users can get the structural strength results of the serialized truss through automatic modelling calculation only by inputting parameters. While satisfying the structural strength of the truss, the analysis process is greatly simplified and the analysis efficiency is improved.

PurposeThis study aims to determine the relationship between sectional geometric parameters of a slotted solid rocket propellant on structural integrity and internal ballistic performance of a rocket motor by using response surface method.Design/methodology/approachZero-dimensional (0D) ballistic solver is developed and validated to determine the effects of sectional geometric parameters on internal ballistic performance of a rocket motor. Additionally, effects of these parameters on structural strength of the system are examined by performing linear viscoelastic finite element analysis under plane strain assumption. Results of the 0D internal ballistic analyses are used as an input to the structural analysis.FindingsDifferent response surfaces are constructed to represent the characteristic variation of solid propellant’s structural strength and internal ballistic performance with respect to design variables.Originality/valueCoupled analysis methodology in terms of structural strength and internal ballistic performance presented in this work facilitates many designers who are working on solid rocket motor development. This study represents graphical results summarizing effects of sectional parameters of a slotted grain on both internal ballistic performance and structural strength results. Additionally, graphical results summarizing the effects of sectional parameters on structural strength and internal ballistic performance provide useful information for researchers that lessens design period. Finally, validations presented in this work can also be used as a benchmark reference for different studies.

Morphology, flow and heat transfer in triply periodic minimal surface based porous structures

Improving wind turbine blade based on multi-objective particle swarm optimization

Heart rate variability (HRV) has become popular for assessing improvements in physical fitness, performance, and recovery. The purpose of this study was to assess the ability of HRV metrics to predict strength and cardiovascular performance in a military cohort using data obtained from commercial off-the-shelf (COTS) wearables. (1) Methods: Twenty-four active-duty military personnel (17 males; 7 females), ranging from age 23 to 41 (32.70 ± 4.65), were equipped with a Whoop Strap 3.0, a Garmin Fenix 5, and an Omegawave during a 12-week exercise intervention study. For this experiment researchers focused solely on HRV metrics obtained on scheduled “Gameday” competitions that occurred periodically during the intervention and contained a battery for strength, power, and cardiovascular performance tests. (2) Statistical Analysis: HRV metrics fitted with linear mixed models and applied to a composite strength variable derived following interrogation of performance tests with principal component analysis (PCA). Akaike’s information criterion (AIC) was also used to compare cardiovascular and strength metrics. (3) Results: Results indicated that standard deviation of NN intervals (SDNN)] obtained from Omegawave was the best overall predictor of performance (AIC > 5.00). (4) Conclusion: Our analyses demonstrated that traditional metrics obtained with the Omegawave were the best performance predictors. HRV measured by Omegawave immediately prior to Gameday assessment was inversely related with strength performance, suggesting that a lower HRV was associated with higher performance (p = 0.002). These findings demonstrate the potential influence of timing and raw values utilized on HRV interpretation to predict strength and cardiovascular performance.

Aiming at the damage and failure problem of copper alloy netting structure, the ultimate strength and fatigue performance of the net structure were studied by test method. Based on the research on the ultimate strength of copper wire, through a series of fatigue tests on copper wire and net structure, the fatigue life and failure modes of copper wire and net structure under different loads are analyzed, and their fatigue life curves are also drawn. The results show that the fatigue strength of copper wire and net structure considering corner processing is lower than that of copper wire not considering corner processing, which indicates that corner processing has a great influence on the fatigue strength of actual copper net structure. Compared with the fatigue strength value of 32.8 MPa of the copper net, the fatigue strength value of the net structure decreases to a certain extent (about 14.3%), which indicates that the assembly process of the copper net has certain influence on the fatigue life of the net structure.

The aerodynamic performance, structural strength, and wheel weight are three important factors in the design process of the radial turbine. This paper presents an investigation on these aspects and develops an optimization design approach for radial turbine with consideration of the three factors. The aerodynamic design for the turbine wheel with an inlet diameter of 230 mm for the 100 kW-class microturbine unit is carried out first as the original design. Then, the cylinder parabolic geometrical design method is applied to the wheel modeling and structural design, but the maximum stress predicted by finite element analysis greatly exceeds the yield limit of material. Further, the wheel weight is above 7.2 kg, thus, bringing some critical difficulties for bearing design and turbine operation. Therefore, an integrated optimization design method for radial turbine is studied and developed in this paper with focus on the wheel design. Meridional profiles and shape lines of the turbine wheel are optimized with consideration of the whole wheel weight. Main structural modeling parameters are reselected to reduce the wheel weight. Trade-off between aerodynamic performance and strength performance is highly emphasized during the optimization design. The results show that the optimized turbine wheel gets high aerodynamic performance and acceptable stress distribution with a weight less than 3.8 kg.

The aerodynamic performance, structural strength and wheel weight are three important factors in the design process of the radial turbine. This paper presents an investigation on these aspects and develops an optimization design approach for radial turbine with consideration of the three factors. The aerodynamic design for the turbine wheel with inlet diameter of 230mm for 100kW-class microturbine unit is carried out firstly as the original design. Then, the cylinder parabolic geometrical design method is applied to the wheel modeling and structural design, but the maximum stress predicted by Finite Element Analysis greatly exceeds the yield limit of material. Furthermore, the wheel weight is above 7.2kg thus bringing some critical difficulties for bearing design and turbine operation. Therefore, an integrated optimization design method for radial turbine is studied and developed in this paper with focus on the wheel design. Meridional profiles and shape lines of turbine wheel are optimized with consideration of the whole wheel weight. Main structural modeling parameters are reselected to reduce the wheel weight. Trade-off between aerodynamic performance and strength performance is highly emphasized during the optimization design. The results show that the optimized turbine wheel gets high aerodynamic performance and acceptable stress distribution with the weight less than 3.8kg.

Throughout this book, there has been frequent discussion about the effect of size on the mechanical properties of materials. Usually, strength properties increase with decreasing dimensions, while ductility decreases. Decreasing the dimensions of a material may decrease the size of the grains in polycrystalline materials. The size of single crystals depends on their growth conditions, but, also in this case, decreased size has the same influence on the mechanical properties. The expectation of improved mechanical characteristics, especially in the submicron/nanometer range, however, must be supported by experimental evidence. Experimental evidence has, indeed, indicated the outstanding mechanical properties of nanocrystalline (NC) materials that often show: superstrength, superhardness, improved specific strength and tribological performance (as attested in the literature). This pattern of reduced ductility with increased strength is also indicated in materials having small dimensions; however recently, some cases of substantial ductility were reported in superstrong NC materials undergoing 100% elongation or more without failure. These reported properties, the unique combination of high strength and good ductility, make such materials ideal for applications in a wide range of fields, such as the aviation, automotive and electronics industries, to name just a few. The aim of this chapter is to provide an overview of some of the mechanical properties discussed thus far regarding materials with small dimensions and to characterize their observed behavior.

It is commonplace when architectural designs that require beauty often do not pay attention to the strength of building structures as part of a unity of structures and architecture of buildings, forgetfulness of the part of the building that was originally assumed not to bear the burden in the end should bear the burden causing a new design adjustment. The study of pipe columns as poles on cantilever building structures was studied because of the concerns of the building owner and also the construction executor of the cantilever frame design. The position of the pole as a successor to the load from the roof to the foundation is noticed because the steel material is elastic and also weak against buckling. An examination of the modified section of the frame structure is absolutely necessary to increase the stiffness of the structure, so that the pipe columns with small dimensions according to the architectural design can be maintained.

Problem. The growth in the volume of construction work carried out in the improvement of adjacent territories, playgrounds, and pedestrian paths requires the use of a wide range of small-sized machines for earthwork and road construction, including loaders. The main requirements for small-sized loaders are small dimensions, which makes it possible to perform work in cramped conditions, good maneuverability, light weight, which allows for low pressure on the surfaces on which the equipment moves, ensuring the safety of loading operations, efficiency and economy. These conditions are fully met by a variety of construction equipment that is combined with self-propelled chassis, which have been manufactured for many years at Ukrainian enterprises and used by organizations for the improvement and beautification of urban space. The indisputable advantage of self-propelled chassis over a large number of short wheelbase loaders, which are also widely used in the public utilities sector, is greater stability due to the large wheelbase and the possibility of using additional outriggers installed on the machine, as well as the availability of a self-unloading platform for transporting goods. The operation of small-sized forklifts based on self-propelled chassis in cramped conditions, along with builders performing installation work, requires increased attention to ensuring the strength of the machine's metal structure, so the issue of studying the load of working equipment is an urgent task. Goal. The aim of the study is to develop scientifically based recommendations for reducing the load of small-sized forklift equipment based on the created design scheme, determining the acting forces and stresses, and rational modes of operation of the forklift. Methodology. The design position in which the handle of the working equipment is located horizontally and the maximum load acts on it is considered. The design load is the maximum weight of the cargo, taking into account the dynamic coefficient. The calculated position for the boom is the position of the greatest bending moment, i.e. the position at maximum reach. The center of gravity of the boom and handle, as well as the weight of the metal structure, were determined using a computer model. The loads acting in the boom joints are determined using a simplified, calculated, boom scheme, for which We will discard the handle, replacing its action with the corresponding reaction and consider the handle separately to determine this load. Given that the force of action from the boom on the handle will be equal in modulo to the force of action from the handle on the boom, and the reactions in the hydraulic cylinder joints will also be equal, we will depict the diagram of the forces acting on the boom. Results. Based on the developed design schemes of the boom and arm, we studied the loading of working equipment, which was carried out using the created program at variable values of the load weight from 4000N to 4500N, the coefficient of dynamism equal to 1, 1.1...1.5, and the height of the arm section from 0.14 to 0.16 m. The analysis of the research results showed that an increase in the coefficient of dynamism to a value of 1.5 at a load weight of 4500N leads to an increase in the acting force to 6840N, but the stresses are within the permissible limits. Increasing the load with which the forklift operates to 5000N requires an increase in the height of the handle section to 0.15m to ensure that the stresses are within the permissible limits. The analysis of the dependence of the acting stresses on the weight of the load and the coefficient of dynamism made it possible to propose recommendations for rational modes of operation of the forklift, which consist of limiting the load to 4500N and the coefficient of dynamism within 1.3-1.4 with a handle cross-sectional height of 0.14m and a wall thickness of 0.05m. It is also proposed to work without jerks, smoothly at low lifting speeds, within the range of the coefficient of dynamism up to 1.3-1.4. Practical meaning. The developed research methodology is proposed for use in the operation of a small-sized forklift in various modes, as well as in the design of working equipment for forklifts of a similar class and design.

We reported previously, in porcine coronary arteries, that the novel biodegradable PowerStent Absorb paclitaxel-eluting stent had improved and sustained structural strength and functional performance at one month post-implantation. To report the stent performance at 6-month follow-up. Six PowerStent Absorb and six TAXUS stents were randomly implanted in the left anterior descending and right coronary arteries of six Tibet miniature pigs. Quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS) images were obtained at the time of implantation (T0) and at 6 months (T6). Two animals were sacrificed at T6 for histopathological evaluation. At T6, QCA showed that the mean luminal vascular diameter (mLD) between the PowerStent and the TAXUS stents were similar (2.36 ± 0.38 vs. 2.61 ± 0.31, respectively). Based on the IVUS analysis, the mLD and the mean lumen cross-sectional area (mCSA) in the PowerStent-treated arteries were similar between T0 and T6 (mLD: 2.74 ± 0.13 vs. 2.70 ± 0.20 and mCSA: 6.81 ± 0.62 mm2 vs. 6.68 ± 0.94 mm2). Histopathology showed that the PowerStent stents were well apposed to the vessel wall with no recoil, strut fracture and thrombus formation. The stents were fully covered with a layer of endothelial cells. At six-month post-implantation, the PowerStent Absorb stents maintained their structural strength and functional performance. The development of restenosis was controlled, no stent thrombosis was observed and the stents were fully re-endothelialized. These results suggest the PowerStent Absorb stent is safe and effective for up to 6 months when implanted in porcine coronary arteries.

PurposeThis paper aims to focus on the spatial docking task of unmanned vehicles under ground conditions. The docking task of military unmanned vehicle application scenarios has strict requirements. Therefore, how to design a docking robot mechanism to achieve accurate docking between vehicles has become a challenge.Design/methodology/approachIn this paper, first, the docking mechanism system is described, and the inverse kinematics model of the docking robot based on Stewart is established. Second, the genetic algorithm-based optimization method for multiobjective parameters of parallel mechanisms including workspace volume and mechanism flexibility is proposed to solve the problem of multiparameter optimization of parallel mechanism and realize the docking of unmanned vehicle space flexibility. The optimization results verify that the structural parameters meet the design requirements. Besides, the static and dynamic finite element analysis are carried out to verify the structural strength and dynamic performance of the docking robot according to the stiffness, strength, dead load and dynamic performance of the docking robot. Finally, taking the docking robot as the experimental platform, experiments are carried out under different working conditions, and the experimental results verify that the docking robot can achieve accurate docking tasks.FindingsExperiments on the docking robot that the proposed design and optimization method has a good effect on structural strength and control accuracy. The experimental results verify that the docking robot mechanism can achieve accurate docking tasks, which is expected to provide technical guidance and reference for unmanned vehicles docking technology.Originality/valueThis research can provide technical guidance and reference for spatial docking task of unmanned vehicles under the ground conditions. It can also provide ideas for space docking missions, such as space simulator docking.