Assembly Conditions Research Articles

Operation Recommendations for Tension Joints and Clamps on a 63 kV Overhead Transmission Line Conductor Based on Experimental Tests

This study provides the operation recommendations for the tension fittings used on a 63 kV overhead transmission line conductor based on experimental tests. In this way, the tension fittings, including the dead-end clamp, the mid-span joint, and the repair sleeve, are assembled on the lynx conductor under different faulty and healthy assembly conditions in the laboratory. The lynx conductor is one of the widely used conductors in the 63 kV overhead power lines. The electric current injection test, along with thermal imaging and also tensile test, are conducted on the studied samples. The results show that the surface temperature of the lynx conductor is higher than the surface temperatures of the dead-end clamp and mid-span joint under normal and overload current conditions. Also, the crimping pressure of the aluminum and steel pipes less than the standard value, the crimping length of the steel cores of conductor less than the standard value, and the crimping length of the aluminum pipes more than the standard value can lead to a developmental defect which should be repaired or replaced at the first opportunity of the transmission line service outage. The repair sleeve is under more thermal stress than the dead-end clamp and mid-span joint, even in the standard assembly condition. A slight temperature difference of a repair sleeve compared with the same type fitting may be a severe operating condition. Also, the use of two consecutive repair sleeves to cover the conductor cut strands is not recommended. Furthermore, the loose connection of bolts at the junction of the jumper terminal to the dead-end clamp causes a very high temperature which should be repaired immediately. If the temperature difference between two defective and healthy dead-end clamp or mid-span joint is more than 13 °C, a critical defect is diagnosed; however, the temperature difference between two repair sleeve more than 7 °C indicates a critical operation condition for defective one.

Orientational Wetting and Topological Transitions in Confined Solutions of Semiflexible Polymers

Despite their considerable practical and biological applications, the link between molecular properties, assembly conditions and self-organized structure in confined polymer solutions remains elusive. Here, we explore the lyotropic nematic ordering of semi-flexible chains in spherical confinement for multiple contour lengths across a wide regime of concentrations. We uncover an original crossover from two distinct quadrupolar states, both characterized by regular tetrahedral patterns of surface topological defects, to either longitudinal, latitudinal or spontaneously-twisted bipolar structures with increasing densities. These transitions, along with the intermediary arrangements that they involve, are attributed to the combination of orientational wetting with subtle variations in their liquid-crystal (LC) elastic anisotropies. Our molecular simulations are corroborated by density functional calculations, and are quantified through the introduction of several order parameters as well as an unsupervised learning scheme for the localization of topological defects. Our results agree quantitatively with the predictions of continuum nematic elasticity theories, and evidence the extent to which the folding of macromolecules and the self-assembly of low-molecular-weight LCs may be guided by the same, universal principles.

Methodology for Counter Torque, Power Loss, and Frictional Heat for Brush Seals Under Eccentric Transients

Turbomachinery brush seals are used for achieving close clearance control with the aid of flexible bristles. Frictional forces between bristle tips and rotor surfaces induce counter torque, power loss, and heat generation during turbomachinery transients; all of these determine the overall efficiency, operation life, and stability of turbomachinery application. As a result of manufacturing tolerances, rotor dynamics-induced shaft deflections, and additional gyroscopic loads in aviation engines, eccentric rotor rub occurs toward brush seals in transients, causing partial rotor–seal contact with nonlinear radial interference and uneven tip force distribution. There is an inherent error in the current power loss and frictional heat rate analyses, as well as in counter torque methodologies, since they do not account for the uneven tip force distribution. In this study, a nonlinear radial interference profile of eccentric rotor contact conditions has been derived and its effect on contact angle has been examined with a comparative analysis with concentric rotor expansion. The methodology for counter torque, power loss, and generated frictional heat rate analyses has been detailed, and eccentric condition formulations have been derived with the surface integration of dynamic bristle tip force functions adopted from brush seal dynamic stiffness tests. Analysis of nonlinear interference and uneven contact force profiles has been conducted based on the combined effects of assembly conditions and eccentricity levels. Results obtained using the developed closed-form equations for eccentric rotor contact are compared with concentric rotor expansion and simple eccentric rotor rub analyses, which do not account for uneven tip forces.

Efficient generation of ETX embryoids that recapitulate the entire window of murine egg cylinder development.

The murine embryonic-trophoblast-extra-embryonic endoderm (ETX) model is an integrated stem cell-based model to study early postimplantation development. It is based on the self-assembly potential of embryonic, trophoblast, and hypoblast/primitive/visceral endoderm-type stem cell lines (ESC, TSC, and XEN, respectively) to arrange into postimplantation egg cylinder-like embryoids. Here, we provide an optimized method for reliable and efficient generation of ETX embryoids that develop into late gastrulation in static culture conditions. It is based on transgenic Gata6-overproducing ESCs and modified assembly and culture conditions. Using this method, up to 43% of assembled ETX embryoids exhibited a correct spatial distribution of the three stem cell derivatives at day 4 of culture. Of those, 40% progressed into ETX embryoids that both transcriptionally and morphologically faithfully mimicked in vivo postimplantation mouse development between E5.5 and E7.5. The ETX model system offers the opportunity to study the murine postimplantation egg cylinder stages and could serve as a source of various cell lineage precursors.

Polyelectrolyte-multivalent molecule complexes: physicochemical properties and applications.

The complexation of polyelectrolytes with other oppositely charged structures gives rise to a great variety of functional materials with potential applications in a wide spectrum of technological fields. Depending on the assembly conditions, polyelectrolyte complexes can acquire different macroscopic configurations such as dense precipitates, nanosized colloids and liquid coacervates. In the past 50 years, much progress has been achieved to understand the principles behind the phase separation induced by the interaction of two oppositely charged polyelectrolytes in aqueous solutions, especially for symmetric systems (systems in which both polyions have similar molecular weight and concentration). However, in recent years, the complexation of polyelectrolytes with alternative building blocks such as small charged molecules (multivalent inorganic species, oligopeptides, and oligoamines, among others) has gained attention in different areas. In this review, we discuss the physicochemical characteristics of the complexes formed by polyelectrolytes and multivalent small molecules, putting a special emphasis on their similarities with the well-known polycation-polyanion complexes. In addition, we analyze the potential of these complexes to act as versatile functional platforms in various technological fields, such as biomedicine and advanced materials engineering.

Rational design of elastin-like polypeptide fusion proteins to tune self-assembly and properties of protein vesicles.

Protein vesicles made from bioactive proteins have potential value in drug delivery, biocatalysis, and as artificial cells. As the proteins are produced recombinantly, the ability to precisely tune the protein sequence provides control not possible with polymeric vesicles. The tunability and biocompatibility motivated this work to develop protein vesicles using rationally designed protein building blocks to investigate how protein sequence influences vesicle self-assembly and properties. We have reported an elastin-like polypeptide (ELP) fused to an arginine-rich leucine zipper (ZR) and functional, globular proteins fused to a glutamate-rich leucine zipper (ZE) that self-assemble into protein vesicles when warmed from 4 to 25 °C due to the hydrophobic transition of ELP. Previously, we demonstrated the ability to tune vesicle properties by changing protein and salt concentration, ZE : ZR ratio, and warming rate. However, there is a limit to the properties that can be achieved via assembly conditions. In order to access a wider range of vesicle diameter and stability profiles, this work investigated how modifiying the hydrophobicity and length of the ELP sequence influenced self-assembly and the final properties of protein vesicles using mCherry as a model globular protein. The results showed that both transition temperature and diameter of protein vesicles were inversely correlated to the ELP guest residue hydrophobicity and the number of ELP pentapeptide repeats. Additionally, sequence manipulation enabled assembly of vesicles with properties not accessible by changes to assembly conditions. For example, introduction of tyrosine at 5 guest residue positions in ELP enabled formation of nanoscale vesicles stable at physiological salt concentration. This work yields design guidelines for modifying the ELP sequence to manipulate protein vesicle transition temperature, size and stability to achieve desired properties for particular biofunctional applications.

Direct access to carbamates via acylation of arylamines with dialkyl azodicarboxylates under metal-free conditions.

A novel C-N coupling of various arylamines with dialkyl azodicarboxylates under metal-free conditions for the rapid assembly of carbamates has been achieved. This established protocol features mild reaction conditions, simple operation, broad substrate scope, moderate to excellent yields and good tolerance of functional groups. Moreover, the potential synthetic utility of products was exemplified by a series of intriguing chemical operations.

Pathway complexity in fibre assembly: from liquid crystals to hyper-helical gelmorphs.

Pathway complexity results in unique materials from the same components according to the assembly conditions. Here a chiral acyl-semicarbazide gelator forms three different gels of contrasting fibre morphology (termed 'gelmorphs') as well as lyotropic liquid crystalline droplets depending on the assembly pathway. The gels have morphologies that are either hyperhelical (HH-Gel), tape-fibre (TF-Gel) or thin fibril derived from the liquid crystalline phase (LC-Gels) and exhibit very different rheological properties. The gelator exists as three slowly interconverting conformers in solution. All three gels are comprised of an unsymmetrical, intramolecular hydrogen bonded conformer. The kinetics show that formation of the remarkable HH-Gel is cooperative and is postulated to involve association of the growing fibril with a non-gelling conformer. This single molecule dynamic conformational library shows how very different materials with different morphology and hence very contrasting materials properties can arise from pathway complexity as a result of emergent interactions during the assembly process.

Insight into the self-assembly and gel formation of a bioactive peptide derived from bovine casein

The self-assembling and gelation properties of a bioactive peptide derived from bovine casein (FFVAPFPEVFGK) were studied in the peptide's natural form (uncapped, uncapFFV) and capped with protecting groups added to both termini (capped, capFFV). Although the natural peptide (uncapFFV) did not demonstrate self-assembly, the capped peptide (capFFV) spontaneously self-assembled and formed a self-supporting gel. Variations in peptide concentration and incubation time influenced the gel's mechanical properties, suggesting the peptide's properties could be tuned and exploited for different applications. These results suggest that food-derived bioactive peptides have good potential for self-assembly and therefore utilisation as gels in functional foods and nutraceuticals. Self-assembly is a natural phenomenon that occurs in many fundamental biological processes. Some peptides can self-assemble and form gels with tunable properties under given conditions. These properties, along with peptide bioactivity, can be combined to make unique biomaterials. Instead of synthesising the self-assembling bioactive peptides, we aim to extract them from natural sources. In order to use these peptides for different applications, it is essential to understand how we can trigger self-assembly and optimise the assembly conditions of these peptide gels. The self-assembling and gelation properties of a bioactive peptide derived from bovine casein (FFVAPFPEVFGK) were studied in the peptide's natural form (uncapped, uncapFFV) and capped with protecting groups added to both termini (capped, capFFV). Although the natural peptide (uncapFFV) did not demonstrate self-assembly, the capped peptide (capFFV) spontaneously self-assembled and formed a self-supporting gel. Variations in peptide concentration and incubation time influenced the gel's mechanical properties, suggesting the peptide's properties could be tuned and exploited for different applications. These results suggest that food-derived bioactive peptides have good potential for self-assembly and therefore utilisation as gels in functional foods and nutraceuticals.

Influence of cooling conditions of HTS assembly on the characteristics of a moving maglev system

Background: analysis of the influence of cooling conditions of high-temperature superconducting elements on the power characteristics of a maglev system under conditions of rapidly changing magnetic fields
 Aim: analysis of the influence of cooling conditions of high-temperature superconducting elements on the force characteristics of a magnetic-levitation transport platform under conditions of rapidly changing magnetic fields caused by the inhomogeneity of the magnetic track.
 Methods: numerical analysis of the maglev system was performed by the finite element method in the Comsol Multiphysics engineering simulation software.
 Results: at fast, more than 5 T/s, magnetic field change rates, due to the motion of the superconductor in a magnetic field with a non-uniform local distribution, the preferred method of cooling is the use of cryocooler technology. At rates of change of the magnetic field less than 5 T/s, it is permissible to use liquid nitrogen as a cooler.
 Conclusion: The developed numerical model makes it possible to predict the dynamic characteristics of levitation systems of various scales and can be applied to contactless transport, as well as in rotating machines, including kinetic energy storage devices.

Community assembly history alters relationships between biodiversity and ecosystem functions during restoration.

Relationships between biodiversity and ecosystem functioning depend on the processes structuring community assembly. However, predicting biodiversity-ecosystem functioning (BEF) relationships based on community assembly remains challenging because assembly outcomes are often contingent on history and the consequences of history for ecosystem functions are poorly understood. In a grassland restoration experiment, we isolated the role of history for the relationships between plant biodiversity and multiple ecosystem functions by initiating assembly in three different years, while controlling for all other aspects of community assembly. We found that two aspects of assembly history-establishment year and succession-altered species and trait community trajectories, which in turn altered net primary productivity, decomposition rates, and floral resources. Moreover, history altered BEF relationships (which ranged from positive to negative), both within and across functions, by modifying the causal pathways linking species identity, traits, diversity, and ecosystem functions. Our results show that the interplay of deterministic succession and environmental stochasticity during establishment mediate historical contingencies that cause variation in biodiversity and ecosystem functions, even under otherwise identical assembly conditions. An explicit attention to history is needed to understand why biodiversity-ecosystem function relationships vary in natural ecosystems: a critical question at the intersection of fundamental theory and applications to environmental change biology and ecosystem restoration.

Electrically controllable self-assembly of gold nanorods into a plasmonic nanostructure for highly efficiency SERS.

In this Letter, a method for the rapid and efficient preparation of ultrasensitive detection substrates by assembling gold nanorod suspensions with the application of an alternating current (AC) field is proposed, and it is found that frequency and voltage are the effective means of regulation. A sandwich structure (parallel SiO2 plate) not only effectively slows down the evaporation rate, but also visually reveals the changes in the assembly process. Under the optimal assembly conditions, the sensitivity and uniformity of the substrate to different probe molecules are tested. The Raman detection results experimentally show that the detection limits of Rhodamine 6G (Rh6G), crystal violet (CV), and Aspartame (APM) molecular solutions are 10-14 M, 10-10 M, and 62.5 mg/L, respectively, and the mixed dye molecular solutions can also be effectively distinguished. Furthermore, Rh6G and CV characteristic peaks at 1647 cm-1 and 1619 cm-1 were measured at randomly selected positions, and their relative standard deviations (RSDs) were 5.63% and 8.45%, respectively, indicating that the substrate has good uniformity. The effective regulation of the self-assembly results of nanoparticles will further enhance the practical application effect of surface-enhanced Raman technology and expand the application prospects of this technology.

Missing Detection of The Clutch-Driven Disc Spring Assembly

A detection system for the missing assembly of clutch-driven plate springs is established. The algorithms used in this system, such as point cloud data preprocessing, spring area positioning, and spring missing detection, are studied. Firstly, according to the characteristics of the clutch-driven plate spring point cloud, the Gaussian statistical method is used to eliminate the outliers incurred by system error and other reasons, and the two-sided filtering is performed on the clutch-driven plate spring point cloud that eliminates the outliers to eliminate the noise points with small ups and downs. Then, the theoretical division area is constructed by using the theoretical width between the clutch-driven plate springs and the theoretical width of the springs. Compared with actually recorded positions, the theoretical area is expanded so that the real spring point cloud data are in the corresponding positioning area; finally, the spring in the region is identified by using the characteristics of an inconsistent number of point clouds in different assembly conditions, so as to detect the missing assembly of the clutch-driven plate spring. The experimental results show that the detection accuracy of the clutch-driven plate spring assembly is as high as 100%. It can basically meet the detection requirements for the missing assembly of clutch-driven plate springs.

Assembly state detection technology based on virtual reality for key components of large space deployable mechanism

Aiming at the highly reliable assembly demand of large space deployable mechanisms with complex interface relationships of components such as bars and hinges, the intelligent assembly state detection of components based on Mixed Reality technology was studied. We designed and built the assembly condition detection system of key components of large space deployable mechanisms, realized the installation position detection of key parts with the Histogram of Oriented Gradients and Support Vector Machine as the recognition algorithm of truss joint base and image processing of screws with truss joint. The detection system is applied to the assembly of the large space truss mechanism. The results show that the accuracy of part recognition is 100%. The system can reduce problems of missing or the wrong assembly and improve the automatic level of large space deployable mechanism assembly detection.

Effect of tubulin self-association on GTP hydrolysis and nucleotide exchange reactions

We investigated how the self-association of isolated tubulin dimers affects the rate of GTP hydrolysis and the equilibrium of nucleotide exchange. Both reactions are relevant for microtubule (MT) dynamics. We used HPLC to determine the concentrations of GDP and GTP and thereby the GTPase activity of SEC-eluted tubulin dimers in assembly buffer solution, free of glycerol and tubulin aggregates. When GTP hydrolysis was negligible, the nucleotide exchange mechanism was studied by determining the concentrations of tubulin-free and tubulin-bound GTP and GDP. We observed no GTP hydrolysis below the critical conditions for MT assembly (either below the critical tubulin concentration and/or at low temperature), despite the assembly of tubulin 1D curved oligomers and single-rings, showing that their assembly did not involve GTP hydrolysis. Under conditions enabling spontaneous slow MT assembly, a slow pseudo-first-order GTP hydrolysis kinetics was detected, limited by the rate of MT assembly. Cryo-TEM images showed that GTP-tubulin 1D oligomers were curved also at 36 °C. Nucleotide exchange depended on the total tubulin concentration and the molar ratio between tubulin-free GDP and GTP. We used a thermodynamic model of isodesmic tubulin self-association, terminated by the formation of tubulin single-rings to determine the molar fractions of dimers with exposed and buried nucleotide exchangeable sites (E-sites). Our analysis shows that the GDP to GTP exchange reaction equilibrium constant was an order-of-magnitude larger for tubulin dimers with exposed E-sites than for assembled dimers with buried E-sites. This conclusion may have implications on the dynamics at the tip of the MT plus end.

Sequence Context and Complex Hofmeister Salt Interactions Dictate Phase Separation Propensity of Resilin-like Polypeptides.

Resilin is an elastic material found in insects with exceptional durability, resilience, and extensibility, making it a promising biomaterial for tissue engineering. The monomeric precursor, pro-resilin, undergoes thermo-responsive self-assembly through liquid-liquid phase separation (LLPS). Understanding the molecular details of this assembly process is critical to developing complex biomaterials. The present study investigates the interplay between the solvent, sequence syntax, structure, and dynamics in promoting LLPS of resilin-like-polypeptides (RLPs) derived from domains 1 and 3 of Drosophila melanogaster pro-resilin. NMR, UV-vis, and microscopy data demonstrate that while kosmotropic salts and low pH promote LLPS, the effects of chaotropic salts with increasing pH are more complex. Subtle variations between the repeating amino acid motifs of resilin domain 1 and domain 3 lead to significantly different salt and pH dependence of LLPS, with domain 3 sequence motifs more strongly favoring phase separation under most conditions. These findings provide new insight into the molecular drivers of RLP phase separation and the complex roles of both RLP sequence and solution composition in fine-tuning assembly conditions.

Characterization of the structure and self-assembly of two distinct class IB hydrophobins.

Hydrophobins are small proteins secreted by fungi that accumulate at interfaces, modify surface hydrophobicity, and self-assemble into large amyloid-like structures. These unusual properties make hydrophobins an attractive target for commercial applications as emulsifiers and surface modifying agents. Hydrophobins have diverse sequences and tertiary structures, complicating attempts to characterize how they function. Here we describe the atomic resolution structure of the unusual hydrophobin SLH4 (86 aa, 8.4kDa) and compare its function to another hydrophobin, SC16 (99 aa, 10.2kDa). Despite containing only one charged residue, SLH4 has a similar structure to SC16 yet has strikingly different rodlet morphology, propensity to self-assemble, and preferred assembly conditions. Secondary structure analysis of both SC16 and SLH4 suggest that during rodlet formation residues in the first intercysteine loop undergo conformational changes. This work outlines a representative structure for class IB hydrophobins and illustrates how hydrophobin surface properties govern self-assembly, which provides context to rationally select hydrophobins for applications as surface modifiers. KEY POINTS: • The atomic-resolution structure of the hydrophobin SLH4 was determined using nuclear magnetic resonance spectroscopy. • The structure of SLH4 outlines a representative structure for class IB hydrophobins. • The assembly characteristics of SLH4 and SC16 are distinct, outlining how surface properties of hydrophobins influence their function.

Engineering a mucin coating to promote osteogenic differentiation of BMSCs in vitro and bone formation in vivo through the Wnt/β-catenin pathway

Mucin, a family of glycoproteins, is widespread in the inner linings of various lumen organs and plays key roles in protecting epithelial cells from invasion by foreign species and communicating with the external environment. Here, we demonstrated that Mucin could be engineered as a promising building block in biomaterials with unexpected multifunctionalities by codepositing with procyanidin (PC, a kind of flavanol polyphenol) through a layer-by-layer technique. The process of generating PC/Mucin multilayers was well characterized and monitored, which was controllable by the assembly conditions. The behaviors of bone marrow mesenchymal stem cells (BMSCs), including proliferation, antioxidant ability, and expression of vinculin, were investigated to reveal the role of PC/Mucin multilayers on the osteogenic differentiation of BMSCs. Our data showed that PC/Mucin multilayers promoted osteogenesis-related genes (Col1, ON, OCN and RUNX2) in BMSCs in vitro and bone generation in vivo by activating the Wnt/β-catenin pathway. These findings demonstrate that engineering Mucin might be a new route in the future to implant materials or coatings for bone regeneration.

Condition Monitoring of an All-Terrain Vehicle Gear Train Assembly Using Deep Learning Algorithms with Vibration Signals

Condition monitoring of gear train assembly has been carried out with vibration signals acquired from an all-terrain vehicle (ATV) gearbox. The location of the defect in the gear was identified based on finite element analysis results. The vibration signals were acquired using an accelerometer under good and simulated fault conditions of the gear. The raw vibration signatures acquired from all the possible conditions of the gear train assembly were processed using the descriptive statistics tool. A set of descriptive statistical features were extracted from the raw vibrational signals. This study used a deep learning algorithm based on the tree family, which includes the decision tree, random forest, and random tree algorithms, to classify gear train conditions. Among the tree family algorithms, the random forest algorithm produced maximum classification accuracy of 99%. The decision rules were used to design an online monitoring system to display the gear condition. This study will help to implement online gear health monitoring in ATVs, ensuring the safety of drivers.

Research on the Influence of the Assembly Parameters of the Junction Surface of Ultrasonic Acoustic Components on the Acoustic Performance Parameters

The core of the ultrasonic machining system is the acoustic vibration component. Due to the inconsistency of the assembly conditions between the junction surfaces of the acoustic vibration component, the resonant frequency of the ultrasonic acoustic vibration component after the size adjustment of the ultrasonic horn is low, and the Impedance mismatch occurs in the ultrasonic system. In this paper, considering the influence of assembly conditions, the optimal assembly parameters were studied to reduce the junction surface’s influence on the ultra-sonic horn’s performance parameters. The paper analyzed the assembly structure, assembly parameters, and static and dynamic performance parameters of the acoustic vibration components and established a static and dynamic performance parameter measurement system. The assembly parameters of the ultrasonic acoustic vibration components were analyzed and determined. The static performance parameters of the ultrasonic acoustic components were measured and analyzed for the assembly parameters of the junction surface at the ultrasonic horn and the straight-edged knife. The optimal assembly parameters were preliminarily determined based on the analysis of the static performance parameters. The optimal assembly parameters of the junction surface of the ultrasonic horn and the straight-edged knife were determined through the measurement and analysis of the dynamic performance parameters of the two junction surfaces. The work is the basis for the adjustment of the ultrasonic horn. It also provides a basis for improving the working performance, manufacturing precision, and production efficiency of the ultrasonic horn while further popularizing the application of ultrasonic processing.