Large Elements Research Articles

Bridging the Gap Between Labour Unions and the Management Through Leadership Development Programs?

AbstractIn this paper we explore if leadership development programs can be applied to bridge the gap between labour unions and the management. By describing and discussing three different programs we can see that joint leadership development programs can promote collaboration between labour unions and the management. The paper argues that such programs need to be built on a premise that more actors than just formal managers can exercise leadership and contribute to organizational development. The paper also discusses why such programs are more easily achievable in a Norwegian setting. However, to make lasting improvements leadership development programs also need to include large organizational development elements, like the co-generative learning model (Elden and Levin (1991) Participatory Action Research. Sage, Newbury Park, pp 127–142). Sufficient time, resources and focus, including assessments of employees’ needs and internal politics, is needed to not only bridging the gap between labour unions and the management, but also to bring in “ordinary” employees.

ANALYSIS OF REINFORCED BOLTED JOINTS IN HIGH-CAPACITY SILOS

ABSTRACT: This paper presents an analysis of the mechanical performance of bolted joints used in silos for storing bulk materials. In particular, we investigated the effectiveness of three types of bolted joints: one without reinforcement, one with angular reinforcement, and one with squared reinforcement. Our analysis involved the use of the finite element analysis sub-modeling technique, which allowed us to construct a large finite element model with shell elements and a sub-model with solid elements. By analyzing the stress state of each joint, we were able to determine the contact state and contact pressure of the bolted joint. Our findings showed that bolted joints reinforced with triangular and square plates were effective in maintaining contact pressure, even under high-pressure conditions. This study provides valuable insights into the design of bolted joints used in silos, which can help ensure their reliable and safe operation. Keywords: bolted joints, high-capacity silo, FEA sub-modeling.

Finite element analysis of large deformation for progressive failure of soil based on Cosserat continuum theory

The large deformation accompanied by strain softening and strain localization of the material is usually encountered in geotechnical engineering. Integrating the RITSS method and the Cosserat continuum theory, a large deformation Cosserat-RITSS finite element method is developed to tackle this issue. Based on the second development interfaces of UEL and SDVINI offered by the finite element software ABAQUS, the Cosserat-RITSS method adopting the MUEM interpolation and mapping method is realized automatically and used to simulate the problem of progressive failure and large deformation characterized by strain localization. The accuracy and effectiveness of the proposed method are verified by the comparison of the small deformation and the large deformation analysis of the penetration process of a rigid strip foundation. Further, the Cosserat-RITSS method is used to analyze the large deformation of a retaining wall resisting on the soil with non-associated plastic flow and strain-softening properties. Compared with the classical RITSS method, it is demonstrated that the proposed method has better performancy of simulating large deformation and overcoming the pathological mesh-dependent problem usually suffered in the classical FEA of large deformation accompanied by strain localization.

Highly asymmetrically configured single atoms anchored on flame-roasting deposited carbon black as cathode catalysts for ultrahigh power density Zn-air batteries

Iron group element-based single atom (SA) catalysts are highly regarded as promising alternatives to commercial Pt/C for catalysis of oxygen reduction reaction (ORR). For applications in rechargeable zinc-air batteries (ZABs), achieving the necessary high catalytic efficiency of the SAs toward oxygen evolution reaction (OER) however remains a significant challenge. Here, highly asymmetrically configured Fe SAs created with N,S co-coordination and anchored on flame-roasting deposited carbon black (CB), Fe-N3S1/CB, are developed, achieving outstanding bifunctional oxygen catalytic efficiency, with an ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10), outperforming the (Pt/C+RuO2) composite catalyst (0.697 V). With a newly proposed binder-free composite air cathode design, the Fe-N3S1/CB based ZAB achieves an ultrahigh power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2, largely outperforming the (Pt/C+RuO2) based ZAB (225.9 mW cm-2 at 344.7 mA cm-2). Furthermore, the Fe-N3S1/CB based ZAB demonstrates excellent long-term stability, with only 8.2% decay in round-trip efficiency over 1000 (333.3 h) charge-discharge cycles at 10 mA cm-2. Density functional theory calculations elucidate that incorporation of sulfur into the coordination sphere of Fe facilitates the electrochemical dehydroxylation step for ORR and accelerates the electrochemical O2 desorption step for OER, thereby reducing the corresponding free energy differences on Fe SAs for largely enhanced catalytic efficiency.1. A large size hetero-atom element, sulfur, is introduced to create highly asymmetrically configured Fe single atoms for enhancements in catalytic efficiency toward both oxygen reduction reaction and oxygen evolution reaction, and a binder-free composite air cathode design is proposed to improve electrochemical performances of zinc-air batteries.2. An ultra-small potential gap of 0.661 V at 10 mA cm-2 (ΔE10) is achieved for the air cathode, and an ultrahigh discharge power density of 365.7 mW cm-2 at a current density of 511.3 mA cm-2 is acquired for the zinc-air battery.

Estimation of breakout force of spudcan footing in structured clay

For a jack-up rig installed in cohesive soil, assessing the extraction force is critical to ensure the safe and successful retrieval of each spudcan footing. The extraction force depends on the preceding stages, including installation and operation of the rig, due to soil strength changes around the spudcan. To investigate the entire ‘penetration - operation - extraction’ process of spudcan, an effective stress large deformation finite element analysis is conducted, with a Structured Cam-Clay model being incorporated to describe the behaviour of structured soil. The large deformation approach is validated against existing centrifuge tests. Parametric studies are then carried out to explore the influential factors on breakout force, including operation period, vertical load ratio, penetration depth, destructuring rate and soil sensitivity. A unique curve is formulated to predict the evolution of the recovery degree of breakout force over the operation period in structured cohesive soil. The soil sensitivity is identified as the dominant factor that affects the ultimate net resistance ratio, which is the key parameter required in applying the prediction curve. A simple method is proposed to estimate the ultimate net resistance ratio and a procedure to predict the breakout force is suggested.

Large Orbital Moment and Dynamical Jahn-Teller Effect of AlCl-Phthalocyanine on Cu(100).

Submonolayer amounts of chloroaluminum-phthalocyanine on Cu(100) were studied with scanning tunneling spectroscopy. The molecule can be prepared in a fourfold symmetric state whose conductance spectrum exhibits a zero-bias feature similar to a Kondo resonance. In magnetic fields, however, this resonance splits far more than expected from the spin of a single electron. Density functional theory calculations reveal a charge transfer of 1.3 electrons to the degenerate lowest unoccupied molecular orbitals. These orbitals are mixed by the orbital momentum operator L[over ^]_{z} with a large matrix element corresponding to m_{L}≈2.7. Dehydrogenation of a ligand lifts the degerenracy of the lowest unoccupied molecular orbital, reduces the splitting in magnetic fields, and induces a polarity dependence of the spectra. Using model calculations of the spin, orbital, and vibrational degrees of freedom we show that a dynamical Jahn-Teller effect reproduces the main experimental observations.

Single elemental planar light concentrator using skewed V-groove optics

Light concentrators are widely used to address the challenges of solar radiation's limited energy density. However, traditional light concentrators suffer from bulkiness, higher focal length, low solar acceptance, and cost factor due to the usage of large imaging optics elements. Waveguide-based planar light concentrators (PLC) have been engineered as a solution to these challenges. They work by collecting light at the incident face and channeling it to the lateral face of the waveguides. However, the existing PLC designs mostly consist of multiple optics elements, resulting in the need for precise positioning and point-to-point solar tracking. Addressing these complexities, a new design for waveguide-based PLC is presented. It features a simplified array of skewed V-grooves within an optical slab, essentially creating a single elemental optics. This novel skewed V-groove-based PLC (SV-PLC) introduces a low-concentration (i.e., <10X geometric concentration (GC)) solution that offers high angular acceptance along one axis. The current study aims to establish the novel design concept, validate, optimize, and assess the design through the Ray-tracing simulation. Further, based on the simulation results, a functional prototype was successfully fabricated in PMMA using laser machining. The results of the optical characterization of the SV-PLC showed that the Optical Efficiency (OE) was approximately around half the theoretical OE. Angular-dependent ray trace results showed a lower OE drop (<10 %) for incident angles less than 15°, and a maximum drop of 30 % (for a 10X GC design) for an incident angle of 23.5° (i.e., half the angle shift of the sun through seasons).

Computational Shape Design Optimization of Femoral Implants: Towards Efficient Forging Manufacturing

Total hip replacement is one of the most successful orthopedic operations in modern times. Osteolysis of the femur bone results in implant loosening and failure due to improper loading. To reduce induced stress, enhance load transfer, and minimize stress, the use of Ti-6Al-4V alloy in bone implants was investigated. The objective of this study was to perform a three-dimensional finite element analysis (FEA) of the femoral stem to optimize its shape and analyze the developed deformations and stresses under operational loads. In addition, the challenges associated with the manufacturing optimization of the femoral stem using large strain-based finite element modeling were addressed. The numerical findings showed that the optimized femoral stem using Ti-6Al-4V alloy under the normal daily activities of a person presented a strains distribution that promote uniform load transfer from the proximal to the distal area, and provided a mass reduction of 26%. The stress distribution was found to range from 700 to 0.2 MPa in the critical neck area of the implant. The developed computational tool allows for improved customized designs that lower the risk of prosthesis loss due to stress shielding.

Mechanical characteristics and structural performance of rubberized concrete: Experimental and analytical analysis

Rubberized concrete is referred to as "green concrete" by replacing fine aggregate with used tire rubber. However, although significantly increasing ductility, rubber particles lowered compressive strength. The study aimed to find the optimum ratio of crumb rubber (C-Ru) to employ in large scale elements. Firstly, the effect of C-Ru treatment and content on concrete mechanical behavior is examined. The experimental program contains 96 cubes and 78 cylinders using different percentages of untreated/treated C-Ru with portions from 5 % to 30 % replacing the sand. Then, four beams were produced with 5, 10, and 15 % sand volume substitution by C-Ru to investigate the effects of rubber content on structural performance and compared with conventional beam. It is found that C-Ru treatment has less enhancement for concrete fresh properties (workability) for using small ratios of rubber and this enhancement increases to reach 20 % for higher rubber content ratio while the comparable enhancement for hardened properties (compressive strength). In addition, well washing of the C-Ru after treatment did not affect the fresh RuC properties, while the improved the hardened properties of RuC (compressive and tensile strengths). Increasing the C-Ru content ratio decreased concrete fresh and hardened properties. Untreated C-Ru not more than 15 % as a replacement of fine aggregates is preferred to avoid large strength reductions while benefiting workability, economy, and safety. While the addition of C-Ru to the concrete mix increased the ductility, toughness, and self-weight of the beams, it also decreased their flexural capacity. Finally, the finite element analysis using ANSYS is used to compare with experimental results and thus it could accurately model behavior of rubberized concrete as a complex material that recommended for further studies.

P-Numerical Semigroups of Triples from the Three-Term Recurrence Relations

Many people, including Horadam, have studied the numbers Wn, satisfying the recurrence relation Wn=uWn−1+vWn−2 (n≥2) with W0=0 and W1=1. In this paper, we study the p-numerical semigroups of the triple (Wi,Wi+2,Wi+k) for integers i,k(≥3). For a nonnegative integer p, the p-numerical semigroup Sp is defined as the set of integers whose nonnegative integral linear combinations of given positive integers a1,a2,…,aκ with gcd(a1,a2,…,aκ)=1 are expressed in more than p ways. When p=0, S=S0 is the original numerical semigroup. The largest element and the cardinality of N0∖Sp are called the p-Frobenius number and the p-genus, respectively.

Transient Shutdown Cooling Simulation of a Gas Turbine Test Rig Configuration Under Ventilated Natural Convection

Abstract A transient simulation of shutdown cooling for a gas turbine test rig configuration under ventilated natural convection has been successfully demonstrated using a coupled aero-thermal approach. Large eddy simulation (LES) and finite element analysis (FEA) were employed for fluid domain computational fluid dynamics (CFD) and solid component thermal conduction simulation, respectively. Coupling between LES and FEA was achieved through a plugin communicator. The buoyancy-induced chimney effect under the axially ventilated natural convection is correctly reproduced. The hotter turbulent flow in the upper part of the annular path and the colder laminar-type air movement in the lower part of the annulus are appropriately captured. The heat transfer features in the annular passage are also faithfully replicated, with heat flux of the inner cylinder reaching its maximum and minimum at the bottom dead centre (BDC) and the top dead centre (TDC), respectively. Agreement with experimental measurements is good in terms of both temperature and heat flux, and the result of the transient simulation for the shutdown cooling is encouraging too. In addition, radiation is simulated in the FEA model based on the usual grey body assumptions and Lambert?s law for the coupled computation. It has been shown that at the high power (HP) condition, the radiation for the inner cylinder is approximately 11% of its convective heat flux counterpart. The importance of radiation is thus clearly revealed even for the present rig test case with a scaled-down temperature setup.

Optimization of spudcan penetration and influence on caisson foundation

The penetration of spudcans have adverse effects on pre-existing bucket foundations during the blade lifting process of offshore wind power systems, which brings uncertainties for the design and construction of bucket foundations. This study employs the Euler-Lagrange method to explore the influence of spudcan penetration on the adjacent caissons in homogeneous clay within a large deformation finite element (LDFE) model. The LDFE model is validated against centrifuge tests data, with good agreement obtained. Parametric study is then conducted to explore, (i) the influence of the angle between vessel and caissons on the movements of the caisson, and (ii) potential influence factors on the movements of the caisson with an optimal angle between the vessel and caissons, including soil properties, dimensions of caisson and spudcan, and the distance between spudcan and caissons. The results show that 60° is the optimal angle between the vessel and caissons that results in the smallest movement of the caisson, and the caisson foundation inclination angle ranges between 0° and 0.025°, when the pile shoe penetration progress ranges between 0.1 and 1.0. An empirical formula is proposed to predict the rotational angle of caisson with the optimal angle. The study establishes a quantitative approach to assess the influence of the spudcan penetration on existing three-caisson jacket foundations, which provides guidance for the design and construction of offshore wind turbine bucket foundations.

Combined loading of unreinforced and Z-pin reinforced composite pi joints: An experimental and numerical study

Blind predictions of experimental responses of non-reinforced and z-pin reinforced composite pi joints were established using a progressive damage and failure model. The finite element model used a novel mixed-mode cohesive formulation to model intra-laminar and inter-laminar damage. A deliberate meshing strategy was used for cohesive interlayers to capture the interaction between intra- and inter-laminar damage modes. A smeared cohesive zone modeling approach was implemented to efficiently include the effects of z-pinning for the z-pin reinforced specimens. Using material properties obtained through experimental correlation of simpler joint configurations, blind predictions for large element specimens subjected to combined loading (axial compression and push-off loading) were established. To assess the predictive capabilities of the model, experimental and numerical comparisons were made in terms of load-displacement response, critical loads, and failure progression. Comparisons between the experimental results and predictions for the unreinforced joints were found to be in good agreement across the range of compressive loads tested. For the z-pin reinforced joints, initial responses were accurately predicted; however, ultimate loads and the toughening effect of the z-pin reinforcement was overpredicted.

A GWO-ML-based large deformation finite element variable mapping method: An example of RITSS large deformation finite element simulation

The mapping of variables between old and new elements is a crucial aspect of large deformation finite element simulation. However, traditional mapping methods suffer from limited applicability and complex operations. In this study, a novel Gray Wolf Optimization-Machine Learning (GWO-ML) based variable mapping method for large deformation finite element analysis is proposed. This method achieves accurate mapping results without requiring explicit determination of element-to-element positional relationships. Furthermore, it effectively integrates a wider range of integration point information during the mapping process and maintains high prediction accuracy near boundaries with sparse mesh data. The remeshing and interpolation technique by small strain is employed as an illustrative example, wherein a set of automated operations is proposed to control the commercial software ABAQUS through Python scripting for conducting small strain analysis and GWO-ML mapping process. For machine learning models, Multilayer Perceptrons, Random Forest, Extreme Learning Machine, and Support Vector Regression, are compared, where the RF model has excellent computational accuracy and efficiency in terms of performance. The application of this method is investigated in scenarios with various foundation types, motion modes, loading modes, and multi-physics coupling mappings. The results confirm that the method exhibits high accuracy and robustness in simulation processes.

Ultrastructural, metabolic and genetic characteristics of determinants facilitating the acquisition of macrolide resistance by Streptococcus pneumoniae

AimsTo investigate the molecular events associated with acquiring macrolide resistance genes [mefE/mel (Mega) or ermB] in Streptococcus pneumoniae (Spn) during nasopharyngeal colonization. Methods and resultsGenomic analysis of 128 macrolide-resistant Spn isolates revealed recombination events in genes of the conjugation apparatus, or the competence system, in strains carrying Tn916-related elements. Studies using confocal and electron microscopy demonstrated that during the transfer of Tn916-related elements in nasopharyngeal cell biofilms, pneumococcal strains formed clusters facilitating their acquisition of resistance determinants at a high recombination frequency (rF). Remarkably, these aggregates comprise both encapsulated and nonencapsulated pneumococci that span extracellular and intracellular compartments. rF assessments showed similar rates regardless Mega was associated with large integrative and conjugative elements (ICEs) (>23 kb) or not (∼5.4 kb). The rF for Mega Class IV(c) insertion region (∼53 kb) was three orders of magnitude higher than the transformation of the capsule locus. Metabolomics studies of the microenvironment created by colonization of human nasopharyngeal cells revealed a link between the acquisition of ICEs and the pathways involving nicotinic acid and sucrose. ConclusionsPneumococcal clusters, both extracellular and intracellular, facilitate macrolide resistance acquisition, and ICEs were acquired at a higher frequency than the capsule locus. Metabolic changes could serve as intervention targets.

Layered seabed effects on buried pipeline response to ice gouging

In ice gouging analyses, the seabed is often simplified as a uniform material domain, over-looking the potential complexities inherent in layered seabed formations, which are wide-spread in numerous Arctic regions. This study investigates the pipeline response into the distinct seabed configurations, including layered soft over stiff clay, layered stiff over soft clay, and uniformly soft and uniformly stiff compositions, to ice gouging. This was achieved through comprehensive large deformation finite element (LDFE) analysis, employing a Coupled Eulerian Lagrangian (CEL) algorithm. Incorporation of the strain-rate dependency and strain-softening effects involved the development of a user-defined subroutine and incremental update of the undrained shear strength within the Abaqus software. The pipeline is explicitly incorporated into the model, allowing for a detailed investigation of its response to ice gouging phenomena within these layered seabed scenarios. This research demonstrates that simplifying a layered seabed into a uniform can be misleading. Such an approach can lead to significant errors, potentially overestimating or underestimating pipeline response to ice gouging. By incorporating these complexities, engineers can develop more optimized designs with enhanced safety margins in Arctic environments prone to ice gouging phenomena.

Regulation of Transition Metal Doping into Double Perovskite Structure as for a Electrocatalyst in Water Electrolysis

Applying and combining of transition metals to perovskite structure is significantly dealt for improving the electrochemical property. The introduction of transition metals in the active B-site is considered as a useful pathway to regulate the chemical and electronic properties of the perovskites. In this study, a double perovskite structure (A2BB’O6) is designed to apply large ionic radius elements such as tungsten(W) that can not be doped into the general single perovskite structure(ABO3). Tungsten is normally equilibrium in the metallic phase, but tungsten ions rapidly move from 4+ state to the 6+ state in the oxide phase, boosting the electrochemical property. The W-based double perovskite materials are synthesized by a high temperature solid-state method. With a combination of Calcium (Ca) doped in the B-site for structural stabilization, transition metals (Ni, Co, etc.) are doped together as an active site to enhance the electrochemical performance. To analyze the physical and chemical structural characteristics, XRD with Rietveld refinement, XPS and XANES/EXAFS measurements are used. Rotating Disk Electrode (RDE) system is utilized to confirm the electrochemical performance of the prepared samples. Through cyclic voltammetry (CV) and linear sweep voltammetry (LSV) measurements, oxygen involved reactions are carried out to prove possibility on our W-based double perovskite materials as a high performance oxygen electrocatalyst with low-price.

Influence of drainage conditions on piezocone penetration mechanism in offshore clays

ABSTRACT CPTu (piezocone penetration test) is widely used in engineering practice to determine various parameters of clays under partially drained conditions. However, most existing research is based on undrained or fully drained conditions for clays, leading to underestimation or overestimation of soil strength. By applying the Eulerian-Lagrangian large deformation finite element method to analyse the water-soil interaction, the CPTu driving mechanism in offshore saturated soft clays under different drainage conditions is revealed. An advanced hypoplastic constitutive model for clays is used to simulate the nonlinear behaviour of kaolin under different drainage conditions. The generation, accumulation, and dissipation of excess pore water pressure under different drainage conditions are analysed, as well as the influence of excess pore water pressure on cone tip resistance and the effective stress of the soil during the CPTu penetration process.

Partially recrystallized heterostructure via Mo-doping endows CoCrNi medium-entropy alloy with exceptional strength and ductility

CoCrNi medium-entropy alloy (MEA) has excellent ductility, but the low strength at room temperature limits its practical usage. This study proposes an effective strategy to enhance the strength of CoCrNi MEA without apparent loss of ductility via partially recrystallized heterostructures resulted from doping of large atomic radius element, which was substantiated in a Mo-doping (CoCrNi)98Mo2 MEA. Compared with CoCrNi, the strength of (CoCrNi)98Mo2 is remarkably improved, maintaining the high uniform elongation of ∼24%. The yield strength and ultimate tensile strength increased from 950 MPa, 1287 MPa to 1131 MPa, 1564 MPa, respectively. The difference in deformation between the soft recrystallized region (SRR) and the hard non-recrystallized region (HNRR) leads to an excellent hetero-deformation induced (HDI) strengthening. Additionally, it is easier to reach the critical stress of twinning caused by high HDI stress at the interface of SRR/HNRR, which contributes to activation of high-density twins and produce dynamic Hall-Petch strengthening effect.

A Discrete Element Method Calibration Approach for Large Ore-flow Applications

The major constraint for large discrete element method (DEM) simulations is the high demand for computation power. To keep the model in a feasible range of simulation time and to conduct the numerical calculations efficiently, the implemented material can be simplified and upscaled. After this, a calibration of the material is inevitable and sets the link between the simulation model and reality. Therefore, an alternative calibration approach is established in this contribution to mimic the flow behaviour of the original material with multi-spherical DEM particles. The calibration approach utilises flow zone dimensions, which were observed in block-caving operations. Additionally, a passive draw-point is used to calibrate the angle of repose. Applying the calibration approach for Kiruna iron ore showed that, with the help of the calibration approach, the material in the simulation could successfully reproduce the targeted flow zone and angle of repose.