Mechanical Analysis Research Articles

Mechanistic soft-sensor design for protein refolding processes based on intrinsic fluorescence measurements

In protein refolding processes the scarce availability of online measurements hampers effective process monitoring. In this work we developed a mechanistic soft-sensor for protein refolding based on online intrinsic fluorescence measurements of tryptophan and tyrosine. In validation experiments using two model proteins, lactate dehydrogenase (LDH) and galactose oxidase, the soft-sensor showed accurate estimates for the prediction of the total sum of folding products (NRMSE <6.1%) by calculating the changing rate of the average emission wavelength. For refolding of the enzyme LDH it was possible to obtain separate predictions of native protein and insoluble aggregates. The soft-sensor design was further extended by a model-based observer approach using particle filtering to incorporate kinetic formulations as well as physical constraints.The novel approach enabled the analysis of kinetic mechanisms during rapid reaction dynamics and can therefore be seen as an enabler to achieve a better understanding of kinetic refolding mechanisms.

GWAS and WGCNA Analysis Uncover Candidate Genes Associated with Oil Content in Soybean.

Soybean vegetable oil is an important source of the human diet. However, the analysis of the genetic mechanism leading to changes in soybean oil content is still incomplete. In this study, a total of 227 soybean materials were applied and analyzed by a genome-wide association study (GWAS). There are 44 quantitative trait nucleotides (QTNs) that were identified as associated with oil content. A total of six, four, and 34 significant QTN loci were identified in Xiangyang, Hulan, and Acheng, respectively. Of those, 26 QTNs overlapped with or were near the known oil content quantitative trait locus (QTL), and 18 new QTNs related to oil content were identified. A total of 594 genes were located near the peak single nucleotide polymorphism (SNP) from three tested environments. These candidate genes exhibited significant enrichment in tropane, piperidine, and pyridine alkaloid biosynthesiss (ko00960), ABC transporters (ko02010), photosynthesis-antenna proteins (ko00196), and betalain biosynthesis (ko00965). Combined with the GWAS and weighted gene co-expression network analysis (WGCNA), four candidate genes (Glyma.18G300100, Glyma.11G221100, Glyma.13G343300, and Glyma.02G166100) that may regulate oil content were identified. In addition, Glyma.18G300100 was divided into two main haplotypes in the studied accessions. The oil content of haplotype 1 is significantly lower than that of haplotype 2. Our research findings provide a theoretical basis for improving the regulatory mechanism of soybean oil content.

Comparative Analysis of the Inhibitory Mechanism of Aβ1-42 Aggregation by Diruthenium Complexes.

There is a growing interest in the search for metal-based therapeutics for protein misfolding disorders such as Alzheimer's disease (AD). A novel and largely unexplored class of metallodrugs is constituted by paddlewheel diruthenium complexes, which exhibit unusual water solubility and stability and unique coordination modes to proteins. Here, we investigate the ability of the complexes [Ru2Cl(DPhF)(O2CCH3)3]·H2O (1), [Ru2Cl(DPhF)2(O2CCH3)2]·H2O (2), and K2[Ru2(DPhF)(CO3)3]·3H2O (3) (DPhF- = N,N'-diphenylformamidinate) to interfere with the amyloid aggregation of the Aβ1-42 peptide. These compounds differ in charge and steric hindrance due to the coordination of a different number of bulky ligands. The mechanisms of action of the three complexes were studied by employing a plethora of physicochemical and biophysical techniques as well as cellular assays. All these studies converge on different mechanisms of inhibition of amyloid fibrillation: complexes 1 and 2 show a clear inhibitory effect due to an exchange ligand process in the Ru2 unit aided by aromatic interactions. Complex 3 shows no inhibition of aggregation, probably due to its negative charge in solution. This study demonstrates that slight variations in the ligands surrounding the bimetallic core can modulate the amyloid aggregation inhibition and supports the use of paddlewheel diruthenium complexes as promising therapeutics for Alzheimer's disease.

Serum untargeted metabolomics analysis of the preventive mechanism of TAETEA Prebiotea on non-alcoholic fatty liver in rats

Pu-erh tea belongs to the six tea categories of black tea, according to the processing technology and quality characteristics, is divided into two types of raw tea and ripe tea. Raw tea is made from fresh leaves of tea as raw materials, through the process of greening, kneading, sun drying, steam molding and other processes made of tightly pressed tea. Ripe tea is made from Yunnan large-leafed sun green tea, using a specific process, post-fermentation (rapid post-fermentation or slow post-fermentation) processing of loose tea and tightly pressed tea. TAETEA Prebiotea is Puerh Ripe Tea, TAETEA Prebiotea has the effect of increasing insulin level and improving hyperglycemia in mice, and it also has the effect of regulating blood lipids, which can reduce the level of serum total cholesterol (TC) and triglycerides (TG), increase the level of high-density lipoprotein cholesterol (HDL-C), and improve the metabolism of lipids. Therefore, further experiments were conducted by us, and TAETEA Prebiotea was formulated into a suitable dose for the intervention of non alcoholic fatty liver disease (NAFLD) model rats, and at the end of the experiments, the samples of each group of experiments were analyzed and detected by the method of UHPLC-Q-Exactive LC-MS liquid-mass spectrometry methodology, and the relevant metabolites as well as metabolic pathways were analyzed by the method of Non targeted metabolomics analysis. As a result, 71 differential metabolites could be screened, of which 35 differential metabolites were up-regulated after intervention and 36 differential metabolites were down-regulated after intervention. Based on the KEGG pathway enrichment and Pathway Impact bubble diagram analysis, glycine, serine, threonine metabolism, arginine and proline metabolism, protein digestion and absorption, and central carbon metabolism in cancer may be the main metabolic pathways in which TAETEA Prebiotea exerted preventive effects on NAFLD rats, C00148 (Proline), C00300 (Creatine) and C00719 (Betaine) are the differential metabolites that play important regulatory roles.

Experimental Evaluation of Mechanical Properties, Thermal Analysis, Morphology, Printability, and Shape Memory Performance of the Novel 3D Printed PETG‐EVA Blends

Experimental Evaluation of Mechanical Properties, Thermal Analysis, Morphology, Printability, and Shape Memory Performance of the Novel 3D Printed PETG‐EVA Blends

The Influence of the Addition of Basalt Powder on the Properties of Foamed Geopolymers.

Geopolymers are binder materials that are produced by a chemical reaction between silica or aluminum compounds with an alkaline activating solution. Foamed geopolymer materials are increasingly being cited as a viable alternative to popular organic insulation materials. Since the foaming process of geopolymers is difficult to control, and any achievements in improving the performance of such materials are extremely beneficial, this paper presents the effect of the addition of basalt powder on the properties of foamed geopolymers. This paper presents the results of physicochemical studies of fly ash and basalt, as well as mechanical properties, thermal properties, and structure analysis of the finished foams. The scope of the tests included density tests, compressive strength tests, tests of the thermal conductivity coefficient using a plating apparatus, as well as microstructure tests through observations using light and scanning microscopy. Ground basalt was introduced in amounts ranging from 0 to 20% by mass. It was observed that the addition of basalt powder contributes to a reduction in and spheroidization of pores, which directly affect the density and pore morphology of the materials tested. The highest density of 357.3 kg/m3 was characterized by samples with a 5 wt.% basalt powder addition. Their density was 14% higher than the reference sample without basalt powder addition. Samples with 20 wt.% basalt addition had the lowest density, and the density averaged 307.4 kg/m3. Additionally, for the sample containing 5 wt.% basalt powder, the compressive strength exceeded 1.4 MPa, and the thermal conductivity coefficient was 0.1108 W/m × K. The effect of basalt powder in geopolymer foams can vary depending on many factors, such as its chemical composition, grain size, content, and physical properties. The addition of basalt above 10% causes a decrease in the significant properties of the geopolymer.

Radiation-induced preparation of nanoscale CoO@graphene oxide for activating peroxymonosulfate to degrade emerging organic pollutants

In this study, ionizing radiation was used to induce the in-situ formation of highly dispersed nanosized cobalt oxide on the surface of graphene oxide (R-Co-GO), which was highly effective for activating PMS to degrade sulfamethoxazole (SMX). R-Co-GO had the highest catalytic activity when 150 μL cobalt chloride hexahydrate solution was used in the precursor, and the pseudo first-order kinetic constant of SMX degradation was 0.07 min−1 with high mineralization efficiency (63.1 %) and high PMS utilization efficiency. The sulfate radicals and high-valent cobalt oxo were mainly responsible for SMX degradation. Mechanism analysis showed that cobalt active site dominated in PMS activation, which was responsible for the formation of sulfate radicals and high-valent cobalt oxo; while the carbon framework contributed to the formation of singlet oxygen. The R-Co-GO-150 had good catalytic activity and stability in five cycling experiments, in which SMX was completely degraded and the concentration of dissolved Co was below 0.1 mg/L. In addition, the R-Co-GO-150/PMS system could also degrade phenol, bisphenol A, atrazine and nitrobenzene effectively, confirming its wide applicability. This study provided a facile method to uniformly disperse the metal oxides on the surface of carbon materials, and an effective system for the removal of emerging organic pollutants from the actual wastewater.

A control-oriented LPV model of large-scale offshore wind turbines for deloading operation

ABSTRACT This article develops a new control-oriented linear parameter varying (LPV) model, which is a linear state-space model with varying parameters aimed at efficiently representing large-scale offshore wind turbines (LOWTs). Firstly, the LPV model is constructed by the mechanism analysis of a 15-MW direct-drive permanent magnet wind turbine. Subseuently, based on the operational data from FAST, the parameters with unknown values in the LPV model are determined by gain scheduling and parameter estimation. Furthermore, a deloading operation for the active output power regulation of LOWTs is proposed based on coordinating the rotor over-speed control (ROC) and the pitch angle control (PAC).

Corporate social responsibility and labor investment efficiency: evidence from China

PurposeWe expect to provide a complete theoretical framework and large sample evidence on the impact of corporate social responsibility (CSR) on the efficiency of labor investment. We also hope to provide micro-evidence based on labor investment behavior for the two-sided impact of corporate CSR behavior.Design/methodology/approachThis paper measures labor investment efficiency by estimating the difference between actual and expected net hiring of enterprises. CSR is measured on the basis of the CSR score of Chinese listed companies published by Hexun.com. A regression model is constructed to analyze the relationship between CSR and labor investment efficiency. Possible endogeneity problems are controlled by lagging independent variables, propensity score matching method and difference-in-difference method.FindingsResults show that CSR can improve labor investment efficiency by reducing over-hiring and under-hiring in emerging markets. The existence of the mediating effect of agency cost, information disclosure quality and employment fluctuation confirms that CSR improves labor investment efficiency through two mechanisms of corporate governance and labor market friction. The improvement effect of CSR on labor investment efficiency is more significant in non-state-owned, high CEO shareholding ratio and high-average urban wage enterprises.Originality/valueIn conclusion, our study is an important supplement to the existing research on the factors affecting labor investment efficiency. Our research conclusions will be helpful for enterprises in developing countries or enterprises in labor-intensive industries to improve labor investment inefficiency. The conclusion of the mechanism analysis in this paper provides more complete and reliable microscopic evidence for accurately identifying the specific path of CSR's impact on labor investment efficiency. This paper verifies the positive impact of CSR from the perspective of labor investment efficiency in the context of a developing country, which provides evidence for the theoretical conflicts related to CSR based on the effectiveness of enterprise labor investment decisions.

Zwitterionic cellulose nanofibers-based hydrogels with high toughness, ionic conductivity, and healable capability in cryogenic environments

Extreme environmental conditions often lead to irreversible structural failure and functional degradation in hydrogels, limiting their service life and applicability. Achieving high toughness, self-healing, and ionic conductivity in cryogenic environments is vital to broaden their applications. Herein, we present a novel approach to simultaneously enhance the toughness, self-healing, and ionic conductivity of hydrogels, via inducing non-freezable water within the zwitterionic cellulose-based hydrogel skeleton. This approach enables resulting hydrogel to achieve an exceptional toughness of 10.8 MJ m−3, rapid self-healing capability (98.9 % in 30 min), and high ionic conductivity (2.9 S m−1), even when subjected to −40 °C, superior to the state-of-the-art hydrogels. Mechanism analyses reveal that a significant amount of non-freezable water with robust electrostatic interactions is formed within zwitterionic cellulose nanofibers-modified polyurethane molecular networks, imparting superior freezing tolerance and versatility to the hydrogel. Importantly, this strategy harnesses the non-freezable water molecular state of the zwitterionic cellulose nanofibers network, eliminating the need for additional antifreeze and organic solvents. Furthermore, the dynamic Zn coordination within these supramolecular molecule chains enhances interfacial interactions, thereby promoting rapid subzero self-healing and exceptional mechanical strength. Demonstrating its potential, this hydrogel can be used in smart laminated materials, such as aircraft windshields.

Fiscal decentralization, leader localization, and reduction of pollution and carbon emissions —empirical evidence from China's fiscal “province-managing-county” reform

The fiscal system plays an important role in the government's environmental governance efforts. There is currently no consensus on how fiscal structure adjustments impact pollution and carbon reduction. This paper uses China's fiscal “province-managing-county” reform (FPMCR) implemented in 2004 as a quasi-natural experiment, utilizing panel data from 1670 counties in China from 2000 to 2020 to investigate the impact of fiscal decentralization on reduction pollution and carbon emissions (RPCE), as well as its underlying mechanisms. The results show that (1) from 2000 to 2020, China's RPCE shows an overall trend of fluctuating increase, with its value turning positive after 2013. China's RPCE exhibits a spatial pattern characterized by “lower in the north, higher in the south; higher in the east, lower in the west”. (2) After implementing FPMCR, the RPCE levels in reformed counties decreased by −1.44%, showing that reformed county-level governments prioritize economic development over environmental protection. (3) The mechanism analysis found that after implementing FPMCR, reformed counties experienced a 9.16% increase in nighttime light intensity (NLI), and a 3.99% and 4.34% increase in the number of large-scale industrial enterprises (NLIE) and industrial agglomeration (IA), respectively. This suggests that FPMCR leads to radical urbanization and rapid industrialization in counties, which is detrimental to the improvement of RPCE levels. (4) The spatial heterogeneity analysis found that FPMCR's impact coefficient on RPCE levels in the eastern regions is −1.96%, while in the western regions it is −1.16%. This indicates that reformed counties in the eastern regions are more likely to invest expanded fiscal resources in economic development projects, leading to a decrease in RPCE levels. (5) The temporal heterogeneity analysis found that after the promulgation of the “Three-Year Action Plan to Win the Blue Sky Defense Battle” in 2018, the adverse impact of FPMCR on RPCE is completely reversed, leading to a 1.76% increase in RPCE levels. (6) Further analysis reveals that localizing leaders can slow down the promotion of county-level urbanization and industrialization by the FPMCR, benefiting the improvement of RPCE levels. In other words, “the outsider monk will not recite scriptures as well as a local one”. This study has clarified the causal relationship and underlying mechanisms between fiscal decentralization and environmental governance, providing reliable theoretical support for optimizing grassroots fiscal systems and reducing environmental pollution in other transitional economies. It enriches the field of environmental economics related to fiscal decentralization.

The influence and mechanism analysis of aluminum sulfate as an environmentally friendly early strength agent on the properties of cement-based materials

Environmentally friendly chemical admixtures are becoming important in the cement industry. The research objective of this paper is to use aluminum sulfate as an early-strengthening agent to achieve the goals of a large increase in early strength and a reduction in CO2 emissions. The experimental design was as follows: The macroscopic properties and microscopic characteristics of aluminum sulfate were experimentally investigated on five different replacement ratios of 0%, 1%, 2%, 3%, and 4% paste specimens of cement at different ages. The results show that (1) AS4 demonstrated a notable enhancement in early strength, while AS2 and AS3 contributed to increased late-stage strength. Over time, the Ultrasonic Pulse Velocity (UPV) of all samples exhibited a steady rise. Additionally, aluminum sulfate was found to reduce the electrical resistivity of the samples. (2) aluminum sulfate increased the rate of exothermic heat release of samples at induction and acceleration phases, advanced the accumulated heat was high in the samples with high aluminum sulfate content, and the accumulated heat was strongly correlated with the compressive strength. FT-IR and XRD results show that aluminum sulfate promoted the formation of AFt while depleting the CH content, and the TGA results show the content of bound water in the samples increased from Day 1 to Day 28, which had a positive effect on the compressive strength. UHR-SEM results show that increasing aluminum sulfate substitution results in the formation of a denser microstructure. (3) for all the various mixtures, AS2 has the lowest CO2 emissions per unit strength.

Poly(vinyl alcohol) gels cross-linked by boric acid for radiation protection of astronauts

Gels are soft materials composed of hydrophilic polymers cross-linked in water by physical or chemical bonds. Due to their lightweight and water-rich nature, these materials find application in various fields, including the space environment, for radiation protection purposes. In fact, thanks to their high hydrogen content, gels exhibit significant radiation stopping power, resulting in reduced fragmentation of incident particles. This suggests their potential utility in shielding electronic devices and safeguarding astronauts’ health. In this work, cross-linked gels based on poly(vinyl alcohol) (PVA) and boric acid (BA) were fabricated and their properties were investigated using different experimental and modeling techniques. The effect of parameters, such as time and temperature, used for fabricating the PVA/BA gels is assessed. Fourier transform infrared spectroscopy (FTIR) was employed to evaluate the ability of BA to form hybrid interpolymeric bonds with PVA macromolecules. To understand the thermo-mechanical properties and viscoelastic behavior of these gels, dynamic mechanical analysis (DMA) in compression mode was performed. The shielding properties were evaluated in different space radiation environments considering galactic cosmic rays, solar particle events, and low earth orbit radiation using deterministic transport codes. The High charge (Z) and Energy TRaNsport (HZETRN) code was employed to create different cross sections as first output for the selected materials, and then, propagate and transport the ionizing radiation inside the materials. The results highlight several advantages of PVA/BA gels fabricated at room temperature without heat treatments. Firstly, the incorporation of BA allows for a slight increase in water content compared to gels produced without the crosslinker. Additionally, an examination of elastic moduli reveals improved mechanical properties exhibiting approximately twice the elastic modulus of PVA gels. Moreover, the analysis of dosimetry quantities suggests that the radiation protection effectiveness of these gels is comparable to that of pure water, while heat-treated PVA/BA gels exhibit a reduced water content resulting in decreased shielding properties and decreased flexibility. Consequently, PVA/BA gels realized at room temperature appear to be the optimal material between PVA gels and the heat-treated counterparts, making them well-suited for integration into astronaut personal protective equipment.

Persistent changes in calcium-regulating hormones and bone turnover markers in living kidney donors more than 20years after donation.

In a previous study, we observed decreased 1,25-dihydroxyvitamin D levels, secondary hyperparathyroidism, and increased bone turnover markers in living kidney donors (LKDs) at 3months and 36months after kidney donation. In our recent survey-based study, we found no increased risk of fractures of all types but observed significantly more vertebral fractures in LKDs compared with matched controls. To elucidate the long-term effects of kidney donation on bone health, we recruited 139 LKDs and 139 age and sex matched controls from the survey-based participants for further mechanistic analyses. Specifically, we assessed whether LKDs had persistent abnormalities in calcium- and phosphorus-regulating hormones and related factors, in bone formation and resorption markers, and in density and microstructure of bone compared with controls. We measured serum markers, bone mineral density (BMD), bone microstructure and strength (via high-resolution peripheral quantitative computed tomography and micro-finite element analysis [HRpQCT]), and advanced glycation end-products in donors and controls. LKDs had decreased 1,25-dihydroxyvitamin D concentrations (donors mean 33.89pg/mL vs. controls 38.79pg/mL, percent difference = -12.6%; P< .001), increases in both parathyroid hormone (when corrected for ionized calcium; donors mean 52.98pg/mL vs. controls 46.89pg/mL,% difference 13%; P= .03) and ionized calcium levels (donors mean 5.13mg/dL vs. controls 5.04mg/dL; P< .001), and increases in several bone resorption and formation markers versus controls. LKDs and controls had similar measures of BMD; however, HRpQCT suggested that LKDs have a statistically insignificant tendency toward thinner cortical bone and lower failure loads as measured by micro-finite element analysis. Our findings suggest that changes in the hormonal mileu after kidney donation and the long-term cumulative effects of these changes on bone health persist for decades after kidney donation and may explain later-life increased rates of vertebral fractures.

Hericenone C attenuates the second phase of formalin-induced nociceptive behavior by suppressing the accumulation of CD11c-positive cells in the paw epidermis via phosphorylated P65

Hericenone C is one of the most abundant secondary metabolites derived from Hericium erinaceus, under investigation for medicinal properties. Here, we report that Hericenone C inhibits the second phase of formalin-induced nociceptive behavior in mice. As the second phase is involved in inflammation, in a mechanistic analysis on cultured cells targeting NF-κB response element (NRE): luciferase (Luc)-expressing cells, lipopolysaccharide (LPS)-induced NRE::Luc luciferase activity was found to be significantly inhibited by Hericenone C. Phosphorylation of p65, which is involved in the inflammatory responses of the NF-κB signaling pathway, was also induced by LPS and significantly reduced by Hericenone C. Additionally, in mice, the number of CD11c-positive cells increased in the paw during the peak of the second phase of the formalin test, which decreased upon Hericenone C intake. Our findings confirm the possibility of Hericenone C as a novel therapeutic target for pain-associated inflammation.

Characteristics of the Particle Break Process and Its Mechanism Analysis in Fluidized Process

Characteristics of the Particle Break Process and Its Mechanism Analysis in Fluidized Process

Searching for LINCS to Stress: Using Text Mining to Automate Reference Chemical Curation.

Adaptive stress response pathways (SRPs) restore cellular homeostasis following perturbation but may activate terminal outcomes like apoptosis, autophagy, or cellular senescence if disruption exceeds critical thresholds. Because SRPs hold the key to vital cellular tipping points, they are targeted for therapeutic interventions and assessed as biomarkers of toxicity. Hence, we are developing a public database of chemicals that perturb SRPs to enable new data-driven tools to improve public health. Here, we report on the automated text-mining pipeline we used to build and curate the first version of this database. We started with 100 reference SRP chemicals gathered from published biomarker studies to bootstrap the database. Second, we used information retrieval to find co-occurrences of reference chemicals with SRP terms in PubMed abstracts and determined pairwise mutual information thresholds to filter biologically relevant relationships. Third, we applied these thresholds to find 1206 putative SRP perturbagens within thousands of substances in the Library of Integrated Network-Based Cellular Signatures (LINCS). To assign SRP activity to LINCS chemicals, domain experts had to manually review at least three publications for each of 1206 chemicals out of 181,805 total abstracts. To accomplish this efficiently, we implemented a machine learning approach to predict SRP classifications from texts to prioritize abstracts. In 5-fold cross-validation testing with a corpus derived from the 100 reference chemicals, artificial neural networks performed the best (F1-macro = 0.678) and prioritized 2479/181,805 abstracts for expert review, which resulted in 457 chemicals annotated with SRP activities. An independent analysis of enriched mechanisms of action and chemical use class supported the text-mined chemical associations (p < 0.05): heat shock inducers were linked with HSP90 and DNA damage inducers to topoisomerase inhibition. This database will enable novel applications of LINCS data to evaluate SRP activities and to further develop tools for biomedical information extraction from the literature.

Effect of Structural Parameters on Output Characteristics of a Novel Self-Supplied Aviation Intelligent Pump

The aviation intelligent pump system is an effective solution to aircraft hydraulic systems’ inefficient power consumption and temperature increase. A self-supplied aviation intelligent pump (SAIP) has a high power-to-weight ratio and compact structure, making it the optimal choice for an intelligent pump. To analyze the output characteristics of a novel aviation intelligent pump, it is crucial to establish an accurate mathematical model that describes its dynamic characteristics. This can be achieved by analyzing the working principle and exploring the influence of critical parameters. The paper introduces the composition and working principle of a self-supplied electro-hydraulic servo variable displacement pump. It then establishes a mathematical model of the whole pump, with a detailed analysis and modeling of the critical variable mechanism and the swash plate assembly’s load moment. A simulation model was created to examine the impact of crucial structural parameters, such as the offset spring’s stiffness and control piston’s diameter, on the output characteristics of the intelligent pump. An experimental platform was also constructed, and the experimental results confirm the accuracy of the SAIP model presented in this paper. The investigation of the output characteristics fully reveals the dynamic performance of the SAIP. This provides the basis for the subsequent design of high-performance flow and pressure control strategies and aids in researching intelligent aircraft hydraulic systems.

Analysis of Unburned Methane Emission Mechanisms in Large-Bore Natural Gas Engines With Prechamber Ignition

Abstract Although precombustion chambers, or prechambers, have long been employed for improving large-bore two-stroke natural gas engine ignition and combustion stability, their design predates modern analysis techniques. Employing the latest computational fluid dynamics (CFD) modeling techniques, this study investigates the importance of temperature and chemistry for ignition of the main chamber, with an emphasis on eliminating unburned methane. The sensitivity of the ignition and complete combustion to main chamber air/fuel mixture homogeneity was also explored. This study compares the effect of purely thermal ignition, purely chemical ignition, and how their interplay can influence the complete combustion of methane in typical mixtures and in homogeneous distributions of fuel in the combustion chamber. The CFD results demonstrated that temperature and chemistry are equally important in the ignition mechanism, and combining the two phenomena is effective at igniting the main chamber. Reduction of residual methane in the main combustion chamber (MCC) is most effective when chemical intermediates and thermal ignition are combined. A rudimentary analysis of the effect of fuel/air stratification was also conducted, and it demonstrated that a dramatic reduction in methane emissions is observed for homogeneous mixtures. The flow field in the main combustion chamber was shown to create detrimental stratification of the fuel/air mixture, which inhibited complete combustion of the methane in the main chamber. By contrast, in the extreme case of a perfectly homogeneous distribution of both chemical intermediates and fuel in the combustion chamber, it is possible to completely eliminate unburned methane in the main combustion chamber.

Interfacial stress and crack propagation experimental study in mini-LED chip debonding

The ultra-miniaturization trend of chips presents new challenges for non-destructive peeling-off techniques. This study models the mini-LED chip-UV film adhesive system as a micro laminated structure and conducts the interfacial stresses and crack propagation analysis of the structure using theoretical, finite element and experimental methods. The innovations of this paper are the illustration of the negligible effect of size effect on 125 μm x 75 μm x 60 μm chips, and the determination of the technology parameter tuning method to promote chip peeling-off. Firstly, applying the first-order shear deformation theory, and considering the UV-curable acrylic adhesive layer and the UV film as elastic materials, Lamé coefficients are introduced to explore the free vibration of the micro laminated structure. The analyses indicate that the scale effect has an extremely small impact, within 0.5%, on natural frequencies of the 100-micron scale laminated structure with a small length-to-thickness ratio. Thereafter, a three parameter elastic foundation (3-PEF) model of the chip-UV film adhesive structure is established and the interfacial stresses distributions are parametrically analyzed. Additionally, an experimental platform for needle-ejecting chip peeling-off is designed and constructed. Finite element simulation, experimental observations, and image recognition of crack generation and propagation during the peeling process were performed. Results show that cracks are generated at both free ends of the adhesive layer and progressively extended inwards. This is consistent with the 3-PEF analytical solution, in which the stress concentration also occurs at free ends of the adhesive layer. The agreement between theoretical, simulation and experimental results regarding interfacial stresses provides a solid foundation for further analysis of chip peeling-off mechanism.