Mixed Mode Research Articles

Fatigue Performance of Ti-6Al-4V Processed by Wire-Arc Directed Energy Deposition

AbstractTi-6Al-4V has a wide range of applications, but long lead times and low-efficiency processing of the material leads to limitations. Through additive manufacturing, such as wire-arc directed energy deposition, higher processing efficiency, and lower lead times are possible. To fully realize the benefits, an important parameter for application is the fatigue performance, which needs to be better documented and performance shortcomings improved. Currently, available results on fatigue performance of wire-arc directed energy deposition of Ti-6Al-4V are limited. Therefore, wire-arc directed energy deposition of Ti-6Al-4V was used with the following approach. Samples were characterized using scanning electron microscopy and optical light microscopy, and mechanically tested for tensile and fatigue performance. Minimal pore density and a fine α microstructure within coarsened epitaxial columnar β-grains was observed. Additionally, elemental burn-off and oxygen contamination was assessed, showing a loss of 0.2 wt.% aluminum during processing and no oxygen pick-up. Compared to other cold metal transfer-based wire-arc directed energy deposition results available in the literature, the results present significant improvements. Fractography indicated mixed fracture modes, which are likely due to the macro-zones of α having varying orientations. Our work provides an advancement in fatigue performance and processing, further showing the potential of the technology.

Carbon emission reducing and financing strategies of capital-constrained supply chains using equity financing under different power structures

AbstractThis study considers a low-carbon supply chain model comprised of a capital-constrained manufacturer and a retailer under a cap-and-trade system. These two parties can choose from two financing modes: bank financing or mixed financing, in which the latter combines bank financing with equity financing. Two decision-making power structures are formulated, namely the Nash game model and the retailer-led Stackelberg game model. Subsequently, a comparative analysis of equilibrium outcomes for both parties within these power structures is performed, yielding the following insights: (1) In the bank financing mode, retailers find greater profitability in adopting dominance. When emission reduction efficiency is high, manufacturers obtain more profit within a Nash game context. However, when emission reduction efficiency is low, manufacturers accrue more profit in a Stackelberg game context. In the mixed financing mode without cap-and-trade regulations, supply chain participants do not express a preference for any specific game structure. (2) Without cap-and-trade regulation, in both the Nash and Stackelberg game models, the supply chain participants find more profitability in mixed financing when carbon emission reduction efficiency is high. Meanwhile, bank financing proves more profitable when the carbon emission reduction is low. Moreover, this study investigates the impact of wholesale and retail prices of low-carbon products on the financing strategies of the supply chain participants under different power structures and financing modes. Additionally, extended models are considered, including the manufacturer-led Stackelberg game structure and the capital-constrained manufacturer with a certain amount of initial capital.

Mixed mode stress intensity factor analysis on edge cracked FGM plate with different material distribution models by XFEM

Mixed mode stress intensity factor analysis on edge cracked FGM plate with different material distribution models by XFEM

Comparative analysis of profits from Bitcoin and its derivatives using artificial intelligence for hedge

Because there is a discrepancy between how individual investors and investment institutions choose Bitcoin and its new derivatives and Exchange-Traded Funds (ETFs), this paper used Bitcoin and ProShares Bitcoin Strategy ETF (BITO) data and a mixed variational mode decomposition and bidirectional gated cycle unit model to examine the interconnections between Bitcoin and its new derivative ETFs, from which actionable recommendations were developed. As well as conducting financial simulation trading using Bitcoin and BITO, the study expanded to examine other major ETFs. It was found that: (1) Bitcoin data could be employed to forecast and describe BITO; (2) under T+0 trading, Bitcoin was more volatile, profitable, and risky than BITO; and (3) under T+1 trading, Bitcoin was less volatile, profitable, and risky than BITO; however, the T+1 trading was found to have higher volatility, profits, and risk than T+0 trading. This study, therefore, builds a bridge from theory to practice for the prediction and description of new ETFs. Different from previous studies, this study explored the relationships between Bitcoin and BITO using Artificial Intelligence and quantitative financial simulations, which extends the practical and theoretical understanding of the Bitcoin market.

Tensile Strength Property with PdCo-Cu Multi-Layer Lamination and Heat Treatment of MEMS Probe for Probe Card

Cantilever wire probe card has limited to transport high-speed signal because of long wire but it is suitable for inspecting high-current and high voltage semiconductor such as wide band gap (WBG) power semiconductors.Superior mechanical property of a probe card wire is in demand because it is respectively used wafer inspection with in and out pad on the top surface of the power semiconductor wafer. Therefore, in this study, tensile specimens of micro electro-mechanical systems (MEMS) probe alternatively layered and electroplated with palladium (Pd)-cobalt (Co) alloy layers and copper (Cu) layers. MEMS probe was also measured tensile strength and elongation with multi-lamination and heat treatment conditions. Additionally, fractography of fracture surface after tensile test were analyzed using a scanning electron microscope (SEM). As the number of PdCo-Cu multi-layer increased, 11, 15 and 21 layered specimens showed higher tensile strength and longer elongation than 5 layered specimens because of the increase of laminated interface of PdCo and Cu. 7 layered specimen after isothermal aging had higher tensile strength and longer elongation than before isothermal aging. In 5, 11, 15 and 21 layered specimens, the fracture surfaces of tensile test specimens without aging treatment showed a ductile-brittle mixed fracture mode. Fracture surfaces of 7-layered specimen before and after isothermal aging showed a ductile-brittle mixed fracture mode.

Natural Inhibitors of the Polyphenol Oxidase Activity Isolated from Shredded Stored Iceberg Lettuce (Lactuca sativa L.)

Polyphenol oxidase (PPO) is the key enzyme responsible for enzymatic browning. To extend the shelf life of shredded lettuce, knowledge about biochemical PPO properties is required. The characterization of the enzyme from shredded, cold-stored lettuce was performed using pyrocatechol and the endogenous substrate (ES) (lettuce phenolics). The optimum pH and temperature for PPO activity were 5 and 50 °C, respectively. Natural infusions used as the PPO inhibitors (IC50) were ranked as follows: lovage (0.09%), marjoram (0.13%), orange peel (0.14%), oregano (0.15%), basil (0.22%), lemon peel (0.24%), parsley leaves (0.58%), and wheat bran (1.06%). Among well-recognized PPO inhibitors, kojic acid (0.00043%), ascorbic acid (0.00053%), and L-cysteine (0.00085%) were the most effective. Among the metal ions, MgCl2, FeCl2, and CaCl2 at 0.5 mM inhibited the PPO activity most effectively (by 28%, 27%, and 21%, respectively). The substrate used (pyrocatechol/ES) significantly influenced the enzyme inhibition. Using pyrocatechol, the lovage extract acted in a mixed mode (Kmi = 27.8 mM, Vmaxi = 2.03 mU), while the ES acted according to the non-competitive mode (Kmi= 0.57 mg GAE/mL, Vmax = 0.0046 U). The study confirms that natural extracts are more effective than L-cysteine when the ES is used. A pre-storage treatment with an infusion may be potentially used to improve the quality of shredded lettuce.

Are answers affected by data collection on paper or online? The case of Belgian adolescents

Abstract Background In the early 2000s, the prevalence estimations were compared in relation with the mode of data collection, i.e. paper or online. Following the widely spread routine use of connected devices, especially in adolescents, such a monitoring is of interest. Within the 2022 “Health Behaviour in school-aged children” survey in French-speaking primary and secondary schools of Belgium, those participating could choose between paper and online collection. Our objective was to compare a large set of indicators between the two modes after adjusting for the students’ characteristics. Methods After a two-stage random selection of schools and classes, 11,751 10-to-20-year-old adolescents completed the questionnaire either on paper or online. Descriptive analysis and comparisons were conducted using chi2 and multiple logistic regressions adjusted for the students’ sociodemographic characteristics that may vary according to the questionnaire mode. Results Overall, 54.9% of the questionnaires were completed online. The choice of the collection mode provided to the schools’ headteachers was associated with the adolescents’ characteristics. Those who completed the questionnaire online were more likely to be in secondary schools, in Wallonia, and of a more favourable socioeconomic profile. After adjustments, no difference in the indicators regarding health, well-being, substance use, or sleep duration was observed. Conversely, a difference was observed for screen time (internet ≥2h/weekday: 70.4% on paper vs. 72.3% online; adjusted P-value: 0.02), some food groups (daily vegetables: 51.2% vs. 58.0%; P-value<0.001) and body weight status (overweight including obesity: 16.7% vs. 14.0%; P-value<0.001). Conclusions In some circumstances such as data collection in the school setting, mixed modes are still necessary due to operational issues. While most indicators did not show a difference between online and paper collection, potential implications for others need to be further understood. Key messages • Collecting data through online or paper questionnaires does not lead to major differences in prevalence estimates. • With the rise of online surveys, further assessment is required to understand the potential declaration biases.

Identifying At-Risk Factors of a College Course in Blended Mode and a Case Study

A framework was proposed to identify the at-risk factors of college courses in blended mode, offering suggestions for continuous improvement. An indicator system concerning teaching quality characteristics was constructed based on context, input, process, and product (CIPP) model. Subsequently, the group Analytic Hierarchy Process (AHP) algorithm was employed to assign weights to each indicator. Notably, the approach for assessing the consistency of the judgment matrix was improved, with a focus on preserving the initial judgments of the experts to the greatest extent. Finally, results were computed using a fuzzy comprehensive evaluation. Continuous improvements were suggested to enhance the teaching quality of the course and improve student learning outcomes. A typical case study was presented to illustrate the detailed process of the proposed framework. The evaluation results demonstrate its potential as a new tool for understanding blended teaching mode and enhancing learning outcomes across various college courses.

Research on Blended Learning Mode of College English based on the Chaoxing Learning Platform

College English is one of the public courses in many majors in universities. Traditional teaching often adopts the traditional large class approach, with face-to-face teaching between teachers and students. In the context of the development of the Internet, online courses have begun to rise. In addition to the influence of many objective factors, online teaching mode has been favored by many schools. At present, applying the information technology teaching mode to subject teaching has become a trend. This article focuses on college English courses and researches the blended learning mode under the application of the Chaoxing Learning Platform to improve teaching efficiency.

Blended Teaching Design of Hotel Customer Management based on Xuexi Tong

This paper explores the innovative application of a blended teaching mode for the core hotel management course, "Hotel Customer Management" (HCM), utilizing the Xuexi Tong learning platform. This study analyzes the platform's advantages for student learning and propose a comprehensive teaching design that has been implemented and evaluated using qualitative research methods. The results demonstrate that the Xuexi Tong-based blended teaching mode effectively stimulates student learning interest, fosters initiative, promotes deep learning, and cultivates practical abilities. This paper details the teaching design content, implementation process, and evaluation methods, offering valuable insights for promoting and applying blended teaching approaches in hotel management education.

Exploring delamination behavior in carbon nanofiber-reinforced sandwich structures with various corrugated cores: An experimental study on mixed-mode crack growth

In this paper, the delamination behavior between the face sheet and core of sandwich panels under a mixed mode of failure during TPSB (Three-Point Sandwich Beam) testing is investigated. The experiments were conducted on two sets of specimens: one reinforced with 0.25% carbon nanofiber weight and the other consisting of samples without carbon nanofibers. The core of the sandwich structures was made of PVC foam, and the corrugated cores and face sheets were made of glass-epoxy fibers. The investigated specimens had corrugated cores with different geometries, such as trapezoidal, square, and triangular. The Force-Displacement and R-CURVE diagrams of sandwich panels reinforced with and without carbon nanofibers were extracted. The strain energy release rate increased with increasing crack length, and this trend in the mixed mode of failure was generally upward. The strain energy release rate in the sandwich panel reinforced with carbon nanofibers with trapezoidal, square, and triangular corrugated cores increased by 20.7%, 39.8%, and 44.6%, respectively. These findings underscore the potential of carbon nanofiber-reinforced sandwich structures for diverse applications requiring enhanced fracture resistance under varying loading conditions. These structures have many applications in wind turbine blades and aerospace industry.

Investigating the influence of geometric configurations and loading modes on mixed mode I/II fracture characteristics of rocks: Part I-Numerical simulation

The influence of geometric configurations and loading modes is a bottleneck that restricts the accurate determination of rock fracture parameters and the precise understanding of fracture mechanisms. Therefore, the phase field method is employed to analyze the influences of specimen geometry and loading modes on the dimensionless stress intensity factors, peak load, fracture toughness, and crack initiation angle during the rock mixed mode I/II fracture process. Three new configurations of specimens are proposed to test rock mixed mode I/II fracture. The research results indicate that as the prefabricated crack inclination angle increases, the peak load of three-point bending type specimen increases, while the peak load of diametric-compression type specimen decreases. Moreover, the influence of geometric configurations on the fracture parameters of three-point bending specimens is greater than that of diametric-compression disk specimens. The research findings of this work can provide basic supporting data for the establishment of mixed mode I/II fracture testing standards.

Instability analysis of Li-ion battery electrode particles induced by chemomechanical growth using incremental deformation theory

Volumetric swelling due to lithiation into active battery materials is a well-known phenomenon. A chemo-mechanical framework can suitably explain the deformations of the electrode and the generation of diffusion-induced stresses (DIS). Various experimental works have shown that the effects of DIS further cause the active material to lose its structural stability. However, relatively few frameworks exist that can investigate such phenomena in a comprehensive manner. These are mainly based on the Euler–Bernoulli beam theory and the von-Karman plate theory. In the present work we present a generalized three-dimensional instability framework incorporating the theory of incremental deformation. We use this theory on a widely used chemo-mechanical framework. Notably, similar existing instability investigations on negative electrode materials are based only on incompressible material behaviour. As opposed to it, in this work we have considered a compressible material. Also, we account for the spatial and temporal nature of growth, which is a significant departure from the existing instability frameworks. Therefore, this current work brings the investigation of structural instability of electrode material closer to physical reality. In our study, we use the compound matrix method to find the critical lithiation parameter. Then we consider three sets of problems, each with a particular combination of boundary conditions applied on the inner and outer cylindrical surfaces of hollow cylindrical anode particles. These are free-free, fixed-free, and free-fixed, where each combination represents a particular type of interaction between an electrode particle and its surroundings. Most importantly, we find that the free-free and fixed-free conditions show only a pure axial and mixed mode of instability, and do not show the pure circumferential mode. The free-fixed conditions, however, shows all three modes of instability. Additionally, the presence of mode crossover makes the instability pattern of such electrode particles significant.

Fatigue life prediction of film-cooling Hole specimens with initial damage

This study investigates a Nickel-based single crystal (SX) superalloy with femtosecond laser-drilled film-cooling holes (FCHs) under varying temperatures (room temperature, 850 °C, and 980 °C), employing a novel framework for predicting fatigue life based on initial manufacturing damage quantification. For all tested anisotropic SX superalloy specimens (including smooth and FCH specimens), the initial damage state is characterized as an equivalent initial flaw size (EIFS), and an EIFS calculation model considering stress concentration is established. Subsequently, the fatigue crack paths and microstructural characteristics of the FCH specimens at different temperatures are analyzed, elucidating crack initiation mechanisms and propagation patterns. A novel incremental plasticity J-integral driving force for fatigue crack propagation is introduced. By incorporating the closure effect of small crack propagation and employing Markov Chain Monte Carlo simulations for determining crack growth rate probabilities, a more accurate expression for the crack growth rate in relation to ΔJfat − ΔJth is derived. This expression comprehensively captures crack patterns on crystallographic planes and Type I mixed mode behavior. Finally, the total fatigue life of the FCH structures, featuring a threefold dispersion zone in both room and high-temperature environments, is predicted through experimental observations and description of crack growth rates. The predicted outcomes significantly outperform those of the conventional life prediction models reliant on crystal plasticity theory.

Formation mechanism and oil-bearing properties of gravity flow sand body of Chang 63 sub-member of Yanchang Formation in Huaqing area, Ordos Basin

Abstract Gravity flow sand body is an important reservoir for deep water deposition. The in-depth study of its formation mechanism and oil enrichment law can provide important guidance for oil and gas exploration in deep water areas. In this article, taking the deep-water gravity flow sand body of the Triassic Chang 63 sub-member in the Huaqing area as an example, the identification characteristics, formation mechanism, and oil-bearing characteristics of the gravity flow sand body are systematically discussed. The results show that sandy debris flow, turbidite flow, and mixed event flow present different superposition combination modes on vertical gravity flow deposition. The lithofacies of the gravity flow sandstone complex are mainly affected by lake level fluctuation, provenance supply, and hydrodynamic conditions. According to the formation conditions, sedimentary types. and distribution characteristics of deep water gravity flow sand bodies, a three-dimensional sedimentary mode of deep water gravity flow sand bodies is established. It is found that the physical and oil-bearing properties of the sandy debris flow sand body are better than those of the turbidity flow sand body. The reason is that the proportion of debris in the sand body of sandy debris flow is high, and the content of debris particles is generally greater than 70% according to the statistics of thin sections, which is conducive to the formation of pores. Second, sandy debris flow belongs to block transport, and the mixing of lithology is not sufficient in the process of block flow transport, so some pores will be preserved. Finally, gravity flows, which are dense at the beginning, become less dense later as detrital sediments unload, allowing them to be transported to distant regions. Therefore, the monolayer thickness of the sandy debris flow sand body is large (generally greater than 0.5 m), and the particle size of the debris ranges from 0.03 to 0.3 mm. Finally, the physical and oil-bearing properties of the sandy clastic flow sand body are better than those of the turbidity flow sand body.

Novel Co2+ and Cd2+ Complexes Derived From a New N‐Donor Pyridyl‐Functionalized Thiophosphoric Triamide Ligand: Structural Investigation, DNA/COVID‐19/Monkeypox Molecular Docking, and Biological Assays

ABSTRACTA thiophosphoric triamide (SPT) ligand P(S)[NH‐2Py]3 was synthesized and utilized as a ligand to make novel binuclear and mononuclear Co2+ and Cd2+ complexes. The compounds are the first examples of discrete chelate SPT complexes with a [N]3P(S)‐based backbone in which the SPT acts as a flexible tridentate N,N,N‐donor or N,N,O‐donor ligand. The metal cation features a hexacoordinate environment M(N)3(Cl)3/M(N)4(O)2 adopting a distorted octahedral geometry. Hirshfeld surface analysis affirms that the pyridinyl nitrogen is a more dominant H‐bond acceptor than the thiophosphoryl sulfur atom. The inhibitory activity against the MDA‐MB‐231 cancer cell line in vitro indicated a good inhibitory effect for all compounds. The mononuclear Co2+ complex showed a stronger inhibitory activity against cancer cells than other studied compounds with an IC50 of 62 ± 1.4 nM. Antioxidant and antihemolytic activity of the compounds showed appreciable performance with the highest activities for the Cd2+ complex. A computational DNA binding study by molecular docking indicated a good affinity of the compounds with the DNA receptor by a mixed mode of interactions. Docking was also performed on SARS‐CoV‐2 and monkeypox (Mpox), resulting in binding energies (−5.5 to −8.9 kcal/mol) that are competitive with current effective drugs.

Improving assessment for work-based learning and degree apprenticeships in business through a co-designed peer review process

Involving students in peer review has substantial benefits for students’ learning and development and, more pragmatically, for staff workload. This paper reports on a student-led effort to co-design a peer review formative assessment task. The assessment is part of a personal development module within a higher education degree apprenticeship programme delivered via blended mode by a business school in South-East England. This case study on student-staff partnership offers a description of the process and a reflection on the impacts from both the student and staff perspective. It suggests that student co-design and peer review activities complement work-based learning, effectively bringing the prior experiences and academic skills of mature/professional students into the classroom.

Research on Blended Teaching of College English Writing Based on 'POA' Theory Under the Background of Big Data

This paper discusses the application value of the writing teaching mode combined with the mixed teaching mode in college English writing teaching against the background of big data. Focusing on production-oriented approach (POA) theory, this paper proposes a mixed learning writing model for English teaching and applies the POA mixed learning English writing teaching model to practical teaching by using the cloud classroom platform, collecting students' big data, and analyzing students' seriousness, classroom participation, satisfaction, and English writing performance. Although the overall student engagement is not high, their classroom satisfaction is very high. Research shows that after the teacher adjusted the lesson plan and encouraged students to participate more in class interactions, their scores improved in the second exam but declined in the third exam . The levels of engagement, participation, and satisfaction have significantly decreased across all grades. The POA combined with the blended learning mode has a great application value in practical teaching in the era of big data.

Mixed Mode‐I/II interlaminar fracture toughness Characterization of woven Carbon–Kevlar interyarn hybrid textile composites

AbstractIn actual service conditions, the composite structures are subjected to the combined effect of Mode‐I and Mode‐II loadings. It has great significance in the aerospace, defense, military, automobile, and marine sectors. This study aims to determine the Mixed Mode‐I/II interlaminar fracture toughness (ILFT) of plain and twill woven carbon, Kevlar monolithic, and interyarn hybrid textile composites under several hybridization schemes. The tailored properties are obtained using the interyarn hybridization of high stiff carbon yarn and high tough Kevlar yarn. The effect of individual yarn in the length direction in different hybrid composite laminates is carefully investigated. The Mixed Mode‐I/II ILFT characterization is experimentally performed using a mixed mode bending (MMB) test specimen on the Instron 8862 system under 45%, 55%, and 65% Mixed Mode ratios (MMRs). The increase in mode mixture percentage decreases the lever length, increases the load‐bearing capacity, and increases the Mixed Mode‐I/II ILFT of the MMB test specimen. Plain woven composites exhibited a higher ILFT than twill woven textile composites. The plain woven carbon–Kevlar hybrid composite laminate with carbon yarn‐in‐length direction shows the highest Mixed Mode‐I/II ILFT after CP laminates. Hybridization significantly increases the Mixed Mode‐I/II ILFT compared to monolithic Kevlar fabric‐reinforced composites. Moreover, the failure mechanisms are investigated using scanning electron microscopy.Highlights Mixed Mode‐I/II ILFT of carbon–Kevlar interyarn hybrid textile composites. ILFT at nonlinearity (NL), VIS, and 5%/Max load points for 45%, 55%, and 65% MMR. Advantage of placing carbon yarn‐in‐length direction in hybrid configurations. Effect of carbon–Kevlar interyarn hybridization on Mixed Mode‐I/II ILFT. Fractography of tested specimens to investigate several failure mechanisms.

Empirical Research on the Assessment and Enhancement of Blended Teaching Competence of Integrated English Teachers

This research aimed to assess Integrated English teachers’ competence at Guangzhou Institute of Science and Technology. The participants of the study were 275 students who were enrolled in Integrated English course, and 11 teachers who teach this course. The study revealed that the level of teachers’ competence in terms of knowledge, skills and attitudes in Integrated English blended teaching was very high as assessed by the teacher and student participants. However, the challenges and problems encountered by teachers were limited time, insufficient supervision on students’ study and difficulty in assessing individual outputs. Therefore, a plan of action was proposed to improve the teaching of Integrated English through blended mode.