Assembly Parameters Research Articles

Updating assembly parameters for spacecraft assembly process state changes: based on data fusion method

Thermal protection systems (TPSs) are important components of reusable spacecraft, and their assembly quality has a crucial impact on flight safety. Owing to the complex assembly process and variable states of spacecraft thermal protection systems, assembly parameters may vary under different assembly states. Therefore, to obtain assembly parameters accurately and efficiently under different assembly states, in this study, 3D point cloud data and fiber optic sensor data were fused to develop an assembly parameter update method for assembly process state changes. Firstly, based on the measured data of thermal protection components and load-bearing structure, the gap, flush and matching parameters solution model are proposed. Secondly, to address the deformation problem of the load-bearing structure caused by changes in assembly status, a fusion method based on laser scanning and sensor detection was devised to achieve deformation prediction of the assembly structure during the assembly process. Thirdly, based on the assembly parameter solution model and point cloud prediction model, a constraint-based assembly parameter optimisation model was established, and an improved quantum particle swarm optimisation (LQPSO) algorithm was employed to achieve assembly parameter updates oriented toward changes in assembly status. Finally, an experimental system for array-based thermal protection structure simulation was established to validate the proposed method. The results show that the proposed parameter update method can achieve ideal results for different assembly state simulation components.

The Research of Diesel Engine Assembly Consistency Influence NOx Emission Based on Uniform Design Method

ABSTRACT Diesel engines need to meet the higher emission requirement according to the Euro VI emission standards, and changes in the assembly tolerance of diesel engines will affect the consistency of nitrogen oxides(NOx) emissions. To study the influence of assembly tolerance on NOx emission, a heavy diesel engine was used as the research prototype. The combustion model of the diesel engine was simulated by the Converge software and calibrated with the bench test data. Because the combustion system parameters have a significant impact on emissions, a three-factor eleven-level uniform design is arranged with three parameters, including compression ratio, fuel injection nozzle extension height and injection advance angle. The regression analysis method is used to obtain the relationship between the parameters and NOx emissions. The R2 test value of the regression equation is 0.916 and the F test value is 43.5, which shows that the results of the analysis are very effective. Then the single factor test method is applied to analyze the varying laws of compression ratio, nozzle extension height and fuel injection advance angle on NOx emissions, and the results reveal the inherent law similar to the regression equation. According to the Euro VI emission standards and the law of diesel engine emission performance consistency, the tolerance variation range of the key dimensions of the assembly parameters is obtained.

Model of evaluation of interference between blades shrouds during assembly of turbine impellers

The workability of the product depends on the quality of the assembly process. Special attention should be paid to the interaction of parts during assembly. In joints where the position of the contacting parts relative to each other is decisive, for effective operation of the product, it is necessary to find the force factors that have the greatest impact on the position of neighboring parts. This is so because due to the influence of the force factor, the parts move and interference and gaps are formed in the joints. For this reason, it is necessary to take into account the deformation of the contacting parts caused by the influence of force factors. The study developed an algorithm for calculating assembly parameters taking into account the rigidity of the contacting parts. On the example of the turbine impeller, a model was obtained that allows predicting the position of the blades under the influence of the force factor, taking into account the rigidity of the system.

Influence of hyaluronic acid and chitosan molecular weight on the adhesion of circulating tumor cell on multilayer films

CD44 is a cell receptor glycoprotein overexpressed in circulating tumor cells (CTCs), with levels linked to an increase in metastatic capacity of several tumors. Hyaluronic acid (HA), the natural ligand of CD44, has primarily been investigated for tumor cell interaction in self-assembled polyelectrolyte multilayer films, with little attention given to the complementary polycation. In this study, we screened sixteen different polyelectrolyte multilayer assemblies of HA and chitosan (CHI) to identify key assembly parameters and surface properties that control and govern CTCs adhesion. Statistics analysis revealed a major role of CHI molecular weight in the adhesion, followed by its combinatorial response either with HA ionization degree or ionic strength. PM-IRRAS analysis demonstrated a correlation between the orientation of HA carboxyl groups on the film surface and CTCs adhesion, directly impacted by CHI molecular weight. Overall, although CTCs binding onto the surface of multilayer films is primarily driven by HA-CD44 interaction, both chitosan properties and film assembly conditions modulate this interaction. These findings illustrate an alternative to modifying the performance of biomaterials with minimal changes in the composition of multilayer films.

Comparative assessment of genotyping-by-sequencing and whole-exome sequencing for estimating genetic diversity and geographic structure in small sample sizes: insights from wild jaguar populations.

Biologists currently have an assortment of high-throughput sequencing techniques allowing the study of population dynamics in increasing detail. The utility of genetic estimates depends on their ability to recover meaningful approximations while filtering out noise produced by artifacts. In this study, we empirically compared the congruence of two reduced representation approaches (genotyping-by-sequencing, GBS, and whole-exome sequencing, WES) in estimating genetic diversity and population structure using SNP markers typed in a small number of wild jaguar (Panthera onca) samples from South America. Due to its targeted nature, WES allowed for a more straightforward reconstruction of loci compared to GBS, facilitating the identification of true polymorphisms across individuals. We therefore used WES-derived metrics as a benchmark against which GBS-derived indicators were compared, adjusting parameters for locus assembly and SNP filtering in the latter. We observed significant variation in SNP call rates across samples in GBS datasets, leading to a recurrent miscalling of heterozygous sites. This issue was further amplified by small sample sizes, ultimately impacting the consistency of summary statistics between genotyping methods. Recognizing that the genetic markers obtained from GBS and WES are intrinsically different due to varying evolutionary pressures, particularly selection, we consider that our empirical comparison offers valuable insights and highlights critical considerations for estimating population genetic attributes using reduced representation datasets. Our results emphasize the critical need for careful evaluation of missing data and stringent filtering to achieve reliable estimates of genetic diversity and differentiation in elusive wildlife species.

Benchmarking the reproducibility of all-solid-state battery cell performance

The interlaboratory comparability and reproducibility of all-solid-state battery cell cycling performance are poorly understood due to the lack of standardized set-ups and assembly parameters. This study quantifies the extent of this variability by providing commercially sourced battery materials—LiNi0.6Mn0.2Co0.2O2 for the positive electrode, Li6PS5Cl as the solid electrolyte and indium for the negative electrode—to 21 research groups. Each group was asked to use their own cell assembly protocol but follow a specific electrochemical protocol. The results show large variability in assembly and electrochemical performance, including differences in processing pressures, pressing durations and In-to-Li ratios. Despite this, an initial open circuit voltage of 2.5 and 2.7 V vs Li+/Li is a good predictor of successful cycling for cells using these electroactive materials. We suggest a set of parameters for reporting all-solid-state battery cycling results and advocate for reporting data in triplicate.

Progressive bearing failure analysis and strength prediction method for the initial assembly and tensile process of composite bolted joints

Composite bolted joints have extensive application in aerospace and marine equipment. Failure analysis and strength prediction are crucial steps in the design of composite bolted joints. This study proposes a method that can accurately analyze the progressive bearing failure and static strength of composite bolted joints under different initial assembly parameters. This method first obtains an accurate initial assembly state based on the high-fidelity finite element model with detailed thread structure. Then it uses this as an input to analyze the progressive bearing failure process and the bearing strength value. Using the above method, the formation and evolution mechanism of the tightening yielding phenomenon during the assembly process are analyzed. And the influence of the two key assembly parameters, washer type and initial bolt tension, on the bearing strength of composite bolted joints is analyzed. The experimental results verify the effectiveness and accuracy of the simulation methods and results.

Investigation of membrane-electrode assembly parameters for double-layer anion-exchange membrane-unitized regenerative fuel cell

In this study, we investigate various membrane-electrode assembly (MEA) parameters in the oxygen and hydrogen electrodes for high-efficiency anion-exchange membrane-unitized regenerative fuel cell (AEM_URFC). The effects of catalyst loadings, types of porous transport layer (PTL), and oxygen and hydrogen catalysts were optimized to improve the efficiency of the AEM_URFC. The PTL results indicated that the PTL suitable for fuel cell (FC) exhibited high round-trip efficiency (RTE). Additionally, the types of hydrogen electrode (Pt/C and PtRu/C) were examined. Additionally, AEM_URFCs with different oxygen reduction reaction (ORR) catalyst types (Pt/C and Pt black), and ORR and oxygen evolution reaction catalyst loadings were evaluated. Through our investigations, we developed a high-efficiency AEM_URFC with an RTE of 65.9 % at 20 mA cm−2 (0.871 and 1.572 V (FC and WE modes, respectively)). Moreover, the performance of this AEM_URFC is superior to that of other AEM_URFCs reported in the literature, which is attributed to the reduced ohmic resistance loss caused by the electrical conductivity and hydrophobicity of carbon PTL. Moreover, the AEM_URFC was durable for 5 cycles, indicating that it is cyclable under URFC operation.

Amphiphilic Nanoscale Antifog Coatings: Improved Chemical Robustness by Continuous Assembly of Polymers.

Designing effective antifog coatings poses challenges in resisting physical and chemical damage, with persistent susceptibility to decomposition in aggressive environments. As their robustness is dictated by physicochemical structural features, precise control through unique fabrication strategies is crucial. To address this challenge, a novel method for crafting nanoscale antifog films with simultaneous directional growth and cross-linking is presented, utilizing solid-state continuous assembly of polymers via ring-opening metathesis polymerization (ssCAPROMP). A new amphiphilic copolymer (specified as macrocross-linker) is designed by incorporating polydimethylsiloxane, poly(2-(methacryloyloxy)ethyl) trimethylammonium chloride (PMETAC), and polymerizable norbornene (NB) pendant groups, allowing ssCAPROMP to produce antifog films under ambient conditions. This novel approach results in distinctive surface and molecular characteristics. Adjusting water-absorption and nanoscale assembly parameters produced ultra-thin (≤100nm) antifog films with enhanced durability, particularly against strong acidic and alkaline environments, surpassing commercial antifog glasses. Thickness loss analysis against external disturbances further validated the stable surface-tethered chemistries introduced through ssCAPROMP, even with the incorporation of minimal content of cross-linkable NB moieties (5mol%). Additionally, a potential zwitter-wettability mechanism elucidates antifog observations. This work establishes a unique avenue for exploring nanoengineered antifog coatings through facile and robust surface chemistries.

Effects of long-term experimental warming on phyllosphere epiphytic bacterial and fungal communities of four alpine plants

The effects of climatic warming on phyllosphere microbial communities remain uncertain. In this study, the effects of long-term (>10 years) experimental warming on phyllosphere epiphytic bacterial and fungal communities of Carex alrofusca, Kobresia pygmaea, Potentilla bifurca and Stipa capillacea were examined in the Northern Tibet. Overall, warming increased bacterial α-diversity, but reduced fungal α-diversity across the four host plants. Warming altered the bacterial and fungal community compositions mainly by increasing Actinobacteria, Firmicutes and pathotroph-saprotroph fungi, and reducing Basidiomycota and symbiotroph fungi across the four host plants. Warming increased the relative effect of the ‘drift & others’ process in the bacterial community, but reduced the relative effect of the ‘dispersal limitation’ process in the bacterial community and the relative effect of the ‘homogeneous selection’ process in the fungal community across the four host plants. The overall warming effects on the bacterial and fungal communities may be due to overall warming effects on temperature, leaf morphology structure and physicochemical properties, ecological processes of community assembly and topological parameters of species co-occurrence networks of bacteria and fungi. Warming altered the bacterial species co-occurrence network mainly by increasing the vertex, clustering coefficient and heterogeneity, while reducing the average path length and network diameter across host species. Warming altered the fungal species co-occurrence network mainly by increasing the network diameter and reducing the vertex across host species. Warming effects on bacterial and fungal communities varied among host plants, which may be due to the diverse responses to warming of plant height, leaf malondialdehyde, ecological processes of community assembly and topological parameters of species co-occurrence network. Therefore, warming can alter phyllosphere epiphytic bacterial and fungal communities of alpine plants. Such changes varied among host plants and may cause adverse effects on the host plants.

Effects of interference fit variation on dynamic characteristics of full ceramic ball bearing rotor system

Bearing fit is one of the key aspects in determining the performance of FCBB (full ceramic ball bearing), which affects FCBB internal contact condition and support stiffness. In this paper, the interference fit value variations of FCBB induced by the centrifugal displacement and thermal deformation is calculated, the mapping relationship between interference fit and internal clearance is established, and the influence of preload and interference fit value on the dynamic characteristics of FCBB is discussed in detail. Finally, the vibration experiment of FCBB is verified by ABLT-9 bearing life testing machine. The research shows that interference fit value is the main factor affecting internal clearance. The increase of internal clearance will reduce the bearing radial stiffness and increase the non-uniformity of load distribution, while the preload will weaken the influence of internal clearance on radial stiffness and load distribution. The results provide a theoretical basis for improving the FCBB’s service performance and optimizing their assembly parameters.

Assembly accuracy prediction method of planetary gear train considering bolt-bearing-shaft-gear coupling effects

Planetary gear train (PGT) is a complex transmission system composed of gears, shafts, bearings and bolted joints, of which the assembly accuracy affects the transmission accuracy and dynamic behavior. In this paper, a new assembly accuracy prediction method is proposed for PGT considering gear-shaft-bearing-bolt coupling effects. The new method is formulated by establishing three models for bolt assembly, shaft error motion and assembly accuracy (transmission error) of PGT. The model for bolt assembly is an original FE-analytical model to analyze the bolt assembly effect on elastic deformation of bearing cap, which is developed by finite element (FE) method and analytical method for addressing the elastic effect of bearing cap and elastic interaction between bolts. The models for shaft error motion and assembly accuracy are performed by the three-dimensional contact analysis with errors and preload of bearing cap based on analytical method and kinematic geometry relationship. Combining the three models, the assembly accuracy can be predicted by simulations. The simulations indicate that the proper bolt assembly parameters can alleviate the influence of manufacturing errors on assembly accuracy. The assembly accuracy tests of PGT are conducted. The results well agree with the simulations’, and the assembly accuracy is improved by the proper bolt assembly parameters.

Influence of impregnation time on TiO2 films sensitized with N719 and 2-Mercaptobenzothiazole: An electrochemical analysis

Dye sensitized solar cells (DSSC) are low-cost photovoltaic devices with easy production. They operate with a photoanode, a photocathode, and an electrolyte responsible for charge permeation within the cell. Recent research focus in DSSCs has aimed at enhancing their energy conversion properties, such as the insertion of new materials to reduce electronic recombination, utilization of gel electrolytes, dye synthesis, and studying cell assembly parameters. This study examined the effects of various immersion durations (6, 12, and 24 h) on TiO2 semiconductor films immersed in solutions containing charge carriers (N719 and 2-Mercaptobenzothiazole). To characterize the electrochemical properties, analyses such as current density versus potential curves (j-V), Electrochemical Impedance Spectroscopy (EIS), charge extraction, Intensity-Modulated Photovoltage (IMVS), and Photocurrent Spectroscopy (IMPS) were performed. It was found that the cell with 24 h of impregnation, presented a higher current density, consequently increasing efficiency (η = 5.76%). Impedance analyses showed that the 24-h samples facilitated charge transport, reducing cell resistance, consistent with charge extraction measurements. Lastly, IMPS and IMVS tests revealed that 24 h of immersion generated shorter collection times (τc = 0.016 ± 0.01) and longer electronic recombination times (τr = 0.07 ± 0.007), aiding the charge transport process.

Study on the key performance and stabilization mechanism of viscoelastic scCO2 foams: The formation of pseudo-gemini surfactants

Worm-like micelles have been recognized as “living polymers,” and their outstanding physicochemical properties provide unique advantages in improving foam stability. Recently, the use of pseudo-Gemini surfactants to create worm-like micelles has garnered substantial attention because of their cost-effectiveness and high performance. However, there is a dearth of research on the key properties of scCO2 foam stabilized by pseudo-Gemini surfactants and the mechanism behind their stabilizing effect. To address this gap, a scCO2 foam system stabilized by worm-like micelles was constructed using pseudo-Gemini surfactants. Through a combination of surface properties, bulk rheology, dynamic light scattering (DLS), and cryo-scanning electron microscopy (Cryo-SEM) measurements, the synergistic effect and foam stabilization mechanism of oleic amidopropyl betaine (OAB) and alpha-olefin sulfonate sodium (AOS) were investigated. The results confirmed the formation of pseudo-Gemini surfactants in the mixed system (OAB + AOS), with superior surface activity compared with individual surfactants. Furthermore, the assembly parameter P = 0.498, determined through interfacial parameter analysis, indicated the self-assembly of worm-like micelles in the mixed system. The rheological properties of the foam liquid, as well as foam drainage, and coarsening experiments showed that the presence of worm-like micelles increased the elasticity of the liquid film, impeding the contraction and expansion of the foam. This resulted in a 145 % increase in the liquid drainage half-life of the scCO2 foam and a 19.3 % reduction in the diffusion rate of scCO2 in the liquid film. Further evidence from DLS and Cryo-SEM confirmed the formation of robust worm-like micelle structures in the OAB + AOS mixed system, enhancing the ability of the liquid film to withstand external disturbances. This study is crucial for advancing the existing understanding of pseudo-Gemini surfactants in terms of improving foam performance and designing effective small-molecule foam fracturing fluids.

Rapid activation of proton exchange membrane fuel cell stack and underlying mechanisms involved

Activation is a crucial procedure to improve the performance of newly fabricated fuel cell stacks to meet the power requirements in actual application scenarios. However, traditional activation procedures generally last for several hours or even days, which greatly increases the cost and limits the production efficiency. In response to this problem, this paper proposes a rapid activation procedure composed of hydrogen pumping (HP) and limiting-current activation with limited air (LCA). The influence of current density for HP and air supply for LCA on activation effect is studied and the best operating conditions are determined. The importance of water supply to the cathode is highlighted during HP. The influence of air supply for LCA on activation effect is limited, which contributes to gas saving. According to the experiments conducted on a single cell and a 10-cell stack, only 40 min are needed with this combined procedure, which is much shorter than that of the traditional step-current activation. Furthermore, nearly 75% of hydrogen is saved due to the short activation time and the control of gas supply, thus significantly reducing the cost during activation. Furthermore, to reveal the underlying mechanisms, membrane electrode assembly parameters before and after activation are obtained by micro-current excitation. A decrease in ohmic resistance and an increase in roughness factor of catalyst are observed, which contribute to performance improvement. According to the characterizations in the microstructure of membrane electrode assembly and platinum catalyst valence state, the electrolyte hydration and oxide reduction are determined as key factors and principles during activation.

Nonlinear error analysis of fast optical delay lines.

Optical delay lines have wide applications in terahertz time-domain spectroscopy and optical coherence tomography. In this study, a fast-rotating optical delay line (FRODL) with 24 turntable reflection surfaces was designed. By analyzing the working principle of the FRODL, a mathematical model was established for the nonlinear parameter error of the FRODL delay time. By constructing the polarization Michelson interference system and testing the FRODL structure, the error of actual assembly parameters of the FRODL was approximately 0.015 mm, the actual delay time of the FRODL was greater than 43.5 ps, and the linearity was 99.785%.

A Systems Approach to Study Collagen Type I Self-Assembly: Kinetics and Morphology.

Collagen type I, the main component of the extracellular matrix in vertebrates, is widely used in tissue engineering applications. This is on account that collagen molecules can self-assemble under certain conditions into 3D fibrillar hydrogels. Although there is an extensive body of literature studying collagen self-assembly, there is a lack of systematic understanding on how different experimental factors, such as pH and temperature, and their cumulative effects guide the self-assembly process. In this work, a comprehensive workflow to study the interactive effects of several assembly parameters on the collagen self-assembly process is implemented. This workflow consists of: 1) efficient statistical sampling based on Design of Experiments, 2) high-throughput and automated data collection and 3) automated data analysis. This approach enables to screen several parameters simultaneously and derive a set of mathematical equationsthat link parameters with the kinetics and morphological aspects of collagen self-assembly, and can be used to design collagen constructs with predefinedcharacteristics.

Simulation of bridge steel structure construction process based on BIM technology

Abstract With the rapid development of computer technology and information technology, bridge engineering is gradually transformed into information technology, and bridge BIM design technology is increasingly concern by the industry. This paper uses BIM technology to simulate the construction process of bridge steel structures. In order to solve the problem that the first model of BIM is too complicated, this paper utilizes the edge folding algorithm and quadratic error metric to refold the model and establish the new vertex coordinates, and at the same time, introduces the folding cost function to maintain the model characteristics. In the simulation experiments of the bridge structure construction, stress changes of the main girder of the bridge body are analyzed in various merging states. When the fitting error is +15mm, +25mm, and +35mm, the stress on the upper edge of the main girder near the top of the pier increases by 0.24MPa, 0.52MPa, and 0.78MPa, respectively, for the selection of materials and the prediction of construction and assembly parameters, in which the length of the steel girder N1 is accurate to the millimeters, which is 39940mm, and the single piece weighs 9,532.5kg. To prevent collision and interference with the bridge pier, the crane should be raised at a height of not less than 6.6m during the lifting stage. It can be seen that BIM technology can not only simulate and predict non-geometric factors such as the materials used but also simulate the margin of error and the bridge stresses as a way to help bridge projects on the ground.

Optimization of Solenoid Parameters for a Magnetic Nozzle Assembly Using Design of Experiments

Optimization of Solenoid Parameters for a Magnetic Nozzle Assembly Using Design of Experiments

Modeling of geological and technical measures based on drilling a well with modified valve assembly parameters

In the course of the research, an analysis of the development of geological and technical measures at various fields was carried out. The justified application of these measures has been studied, and recommendations have been made to increase the efficiency of oil recovery based on drilling wells with modified valve assembly parameters. The conducted research allows us to obtain optimal performance indicators of pumping equipment associated with such parameters as pressure, flow, taking into account the lowest cost of repair work. For this purpose, modeling of geological and technical measures based on drilling a well with modified parameters of the hydraulic assembly of the drilling pump has been developed. This design solution allows you to obtain optimal performance of the drilling pump, taking into account the lowest costs for current and major repairs. These studies aimed at finding optimal geological and technical measures (GTM) related to increasing the productivity of drilling pumps and oil recovery in general are very promising and relevant.