Cap Model Research Articles

Predictive modelling of powder compaction for binary mixtures using the finite element method

Despite the widespread use of solid-form drug delivery within the pharmaceutical industry, tablets remain challenging to formulate because their properties depend strongly on the powder composition and details of the compaction process. Powder compaction simulations, using the finite element method (FEM) in combination with the density-dependent Drucker-Prager Cap model, can be used to aid the design process of pharmaceutical tablets. Parametrisation is typically carried out manually and requires experimental data for each powder considered. This becomes cumbersome when considering different ratios of component powders. An automated parameterisation workflow was developed and validated using experimental powder mixtures of micro-crystalline cellulose and dibasic calcium phosphate dihydrate. FEM simulations reproduced experimental compaction curves with a mean error of 2.5% of the maximum compaction pressure. Moreover, a mixing methodology was developed to estimate parameters of mixtures using only pure-component parameters as input. The experimental compaction curves of mixtures were predicted with a mean error of 4.8%.

Odontogenesis by Endocytosis of Peptide Embedding Bioactive Glass Composite

Limited therapeutic options are available for treating deep caries. Those materials with potential of a dual effect to remineralize hard tissue and regenerate defective dentin tissues could be used as a new strategy for deep caries treatment. However, the application of the single component remains a challenge mainly because they lack calcium and phosphorus, are easily degraded, and are difficult to retain in the intricate body fluid environment. Considering the abundant source of calcium and phosphorus as well as the delivery performance of mesoporous bioactive glass (MBG), an amelogenin-derived peptide (QP5), which has a significant role in hard tissue remineralization, was loaded to fabricate a novel composite. After the synthesis of highly ordered MBG using a sol-gel method, the QP5 peptide was loaded increasingly by its extensive porous structure and enhanced electrostatic absorption. When used in an acidic environment, the MBG/QP5 composite presented pH-responsiveness, releasing therapeutic ions and functional peptides in a sequential cascade, and eventually adjusted the pH to a neutral state. The composite was internalized by dental pulp cells through a clathrin-mediated pathway and influenced by cell membrane lipid raft regulation. It could be also transported through the macro-pinocytotic pathway. Compared to the single treatment of peptide QP5 in 48 h, the composite facilitated a higher level of retention of the intracellular peptides. The composite further promoted migration and odontogenesis of dental pulp cells, including the improved activity of alkaline phosphatase, increased formation of mineralized nodules, and upregulated expression of mineralization-related genes compared to using MBG or QP5 alone. The composite further induced the dentin-like layer in a rat pulp capping model. The results suggested that this intelligent material with pH-responsiveness provides a promising alternative treatment method for biomimetic restoration of deep caries.

The Design and Analysis of the Knee Cap Model Using FEA

The Design and Analysis of the Knee Cap Model Using FEA

Tissue-engineered collagenous fibrous cap models to systematically elucidate atherosclerotic plaque rupture

A significant amount of vascular thrombotic events are associated with rupture of the fibrous cap that overlie atherosclerotic plaques. Cap rupture is however difficult to predict due to the heterogenous composition of the plaque, unknown material properties, and the stochastic nature of the event. Here, we aim to create tissue engineered human fibrous cap models with a variable but controllable collagen composition, suitable for mechanical testing, to scrutinize the reciprocal relationships between composition and mechanical properties. Myofibroblasts were cultured in 1 × 1.5 cm-sized fibrin-based constrained gels for 21 days according to established (dynamic) culture protocols (i.e. static, intermittent or continuous loading) to vary collagen composition (e.g. amount, type and organization). At day 7, a soft 2 mm ∅ fibrin inclusion was introduced in the centre of each tissue to mimic the soft lipid core, simulating the heterogeneity of a plaque. Results demonstrate reproducible collagenous tissues, that mimic the bulk mechanical properties of human caps and vary in collagen composition due to the presence of a successfully integrated soft inclusion and the culture protocol applied. The models can be deployed to assess tissue mechanics, evolution and failure of fibrous caps or complex heterogeneous tissues in general.

Micro-CT study on isolated teeth with hereditary dentin defects.

To construct the three-dimensional structure of the isolated teeth of patients with dentinogenesis imperfecta type Ⅱ (DGI-Ⅱ) and dentin dysplasia type Ⅰ (DD-Ⅰ) by using Micro-CT and explore internal structure and hard tissue mineralization density. The three-dimensional structures of the third molars collected from patients with DGI-Ⅱ and DD-Ⅰ and healthy individuals of the same age were reconstructed by using Micro-CT (Mimics 17.0). The internal structures of the affected teeth along the sagittal and transverse planes were observed. The grayscale values of the enamel, crown dentin, and root dentin were calculated. Then, the mineralization densities of the different parts of the teeth of the three groups were analyzed. The detailed three-dimensional models of the mandibular third molars with hereditary dentin defects were successfully constructed. The models contained the models of the enamel cap, dentin core, and pulp cavity. Sagittal and transverse section scans revealed that in patients with DGI-Ⅱ, the pulp cavity was incompletely calcified and the root canal was narrow, whereas in those with DD-Ⅰ, the pulp cavity and root canal were obliterated and the root of the tooth was absent. The analysis of the grayscale values showed that compared with those in the healthy group, the grayscale values of the enamel, crown dentin, and root dentin were lower in the DGI-Ⅱ and DD-Ⅰ groups (P<0.01). No significant differences in the grayscale values of the enamel and crown dentin were found between the DGI-Ⅱ and DD-Ⅰ groups (P>0.05), whereas the grayscale value of the root dentin showed statistically significant differences between the two groups (P<0.01). The application of Micro-CT provided a simple and accurate method for the three-dimensional structure reconstruction and quantitative analysis of the mineralization density of isolated teeth with hereditary dentin defects. Although the dentin mineralization density of DGI-Ⅱ and DD-Ⅰ teeth decreased, the decrement shown by DD-Ⅰ teeth was more significant than that shown by DGI-Ⅱ teeth. The pulp cavity had abnormal calcifications, and the root canal was narrow or even occluded.

Large-scale shear test of brash ice

A large-scale shear apparatus has been originally developed and built to test the mechanical properties of coarse-grained material. It was used to evaluate the shear behaviour of brash ice. The brash ice blocks were collected at Luleå harbour in two separate measuring campaigns in March 2020 and March 2021. The shear cylinder was loaded with brash ice in Luleå port in two different locations for the two test campaigns, and the displacement-controlled shear tests were conducted. A vertical actuator was used to set a constant normal load and then a horizontal actuator was used to move the shear swing. In this setup, time, forces, and displacements were recorded at the forward and return stroke of the horizontal actuator. In total 6 shear cycles on two brash ice samples with axial stress of 4.8 kPa, 2 kPa and 1 kPa were performed. The test data was analysed to determine the relationship between shear stress and shear strain. The macro-porosity and confining axial force were found to be the most influential factors in determining the strength and deformation of the brash ice. Furthermore, an attempt has been made to estimate a few parameters of a material model known as the Continuous Surface Cap Model.

Robust optimization of sustainable closed-loop supply chain considering carbon emission schemes

In the context of the circular economy, this paper focuses on developing an optimal sustainable Closed-Loop Supply Chain (CLSC) by considering such Carbon Emission Schemes (CESs) as carbon cap, carbon cap-and-trade, and carbon tax. A risk-based robust mixed-integer linear programming is formulated using a scenario-based Conditional Value-at-Risk (CVaR) to deal with demand uncertainty. The results reveal that the model performance is affected by both the Decision-Maker's (DM's) risk-aversion and the CESs. However, in all the CESs, the more conservative the DM, the lower the cost performance, and the greater the cost/solution robustness. The carbon cap-and-trade policy not only has the best cost-performance but, ignoring the very small amount of cost robustness deficit compared to the carbon cap model, can also be considered acceptable in the case of robustness. The cost-saving that the carbon cap-and-trade policy brings to the optimistic DM is greater than that brings to the pessimistic one. However, different levels of the DM's risk aversion have a negligible effect on the cost increase of the carbon tax model compared to the carbon cap one.

PEMBERDAYAAN GENERASI MILENIAL MELALUI KERAJIANAN TANGAN MERAJUT UNTUK MENINGKATKAN PENDAPATAN PADA MASA PANDEMI COVID 19

The COVID-19 pandemic has had an impact on all fields, including the family economy. The purpose of service activities is to carry out a community assistance process to recognize and make knitting skills, and produce products that can be marketed to improve the economy of the community. This service activity is carried out in three ways, namely training, implementation and mentoring. The subject of this service activity is the Youth of Kotangan Village, Galang District, Kab. Deli Serdang. The results of this activity include two things, first, the partner community has increased in terms of knowledge, understanding and skills in and the achievement of increased partner skills in the form of knitted bag models, cap models, mask connector models, as well as hats and skullcaps. Second, the products that have been produced have begun to be marketed through online media in Deli Serdang Regency. The achievement of this service activity is very dependent on the consistency of the partner's spirit to work during this pandemic.

Non-coupled finite element modelling of electromagnetic compaction of Al 6061 powder in Al 6063 tube

Electromagnetic powder compaction is considered a high strain and high-speed powder forming technique. The method uses the Lorentz forces for compacting powder to obtain near net shape and high strength compact through the PM route. This process can be classified as a contactless powder compaction technique since no physical punch is used to form powder for compaction. All kinds of materials, irrespective of the powder particle's hardness and size distribution, can be compacted using this technique. Few materials are tough to compact due to their higher hardness as well the frictional forces are very high during the compaction of Nanosized metallic powder. These barriers can be easily overcome by using high velocity and energy, such as the electromagnetic forming technique. In this paper, a non-coupled finite element model is developed to simulate the electromagnetic powder compaction process of pure Aluminium. ANSYS-Maxwell is used to investigate the electromagnetic field distribution in electromagnetic powder compaction tooling setup. The Geologic Cap model was used in the LS-Dyna Multi-physics solver to describe powder deformation during the compaction process. The Johnson-Cook plasticity model describes the deformation behaviour of the Al 6063 packing tube. Finally, the developed simulation model is validated with experimental results of aluminium powder compacts at 12 kV and 13 kV. The powder compaction experiments were carried out using a 40 kJ capacity electromagnetic forming machine. It found that the simulation results agreed with experimental data results. The comparison is made between the final diameters of the compact obtained through simulation and experiments.

Experimental and Numerical Assessment of the Impact Test Performance Between Two UHSS Toe Cap Models

This paper presents an integrated approach for an ultimate high-performance safety toe cap with significant milestones in slim design and weight saving. The study of crashworthiness properties was performed through impact-crash test conditions exploring the potential of applicant solutions by the combination of an advanced high-strength steel and enhanced geometric stiffening models. The structural response for a significant thickness reduction was assessed and it provides an evolved discussion for improvements in energy absorption capacity. The present case study focuses on two geometric models from the S3 slim toe cap development by prototypes made of a martensitic 1200 steel alloy. The comparison of results is complemented using numerical simulation models with mathematical description of the dynamic plasticity behaviour by applying a constitutive Cowper-Symonds equation with fundamental parameters for material strain-rate dependence.

Single Pile FEM Modeling: Ultimate Capacity Determination of Bored Piles Embedded in Silty-Sands Using Modified Drucker-Prager Cap Model

Ultimate pile capacity determination is crucial before the structure construction. This essential pile resistance can be accurately predicted and studied using the finite element method. FEM is a numerical method that is anticipated to be indispensable in advances in pile analyses, aiming at pile effectiveness and material efficiency. Pile modeling is attainable using FEM for the stability investigation concerning the geotechnical findings. In addition, several constitutive mathematical models have been available for FEM applications to reasonably simulate soil behavior under pressure. This study conducts numerical modeling of eight bored piles of different diameters and lengths embedded in silty-sand soils. Using the FEM software ABAQUS, pile load-settlement curves are obtained to determine ultimate pile capacity, skin friction resistance, and pile base resistance. The modified Drucker Prager Cap model is used as a constitutive soil model for silty sand soils. In applying the MDPC model, the cap hardening behavior (hardening parameter) is obtained by having the site soils compression and swelling indices determined using the proposed regression equations in the literature. Piles were modeled successfully, and the results positively correlate with the results of the dynamic analysis test conducted in Davao del Norte, Philippines.

Blockchain-Enabled Energy Demand Side Management Cap and Trade Model

Global economic growth, demographic explosion, digitization, increased mobility, and greater demand for heating and cooling due to climate change in different world areas are the main drivers for the surge in energy demand. The increase in energy demand is the basis of economic challenges for power companies alongside several socio-economic problems in communities, such as energy poverty, defined as the insufficient coverage of energy needs, especially in the residential sector. Two main strategies are considered to meet this increased demand. The first strategy focuses on new sustainable and eco-friendly modes of power generation, such as renewable energy resources and distributed energy resources. The second strategy is demand-side oriented rather than the supply side. Demand-side management, demand response (DR), and energy efficiency (EE) programs fall under this category. On the other hand, the decentralization and digitization of the energy sector convoyed by the emersion of new technologies such as blockchain, Internet of Things (IoT), and Artificial Intelligence (AI), opened the door to new solutions for the energy demand dilemma. Among these technologies, blockchain has proved itself as a decentralized trading platform between untrusted peers without the involvement of a trusted third party. This newly introduced Peer-to-Peer (P2P) trading model can be used to create a new demand load control model. In this article, the concept of an energy cap and trade demand-side management (DSM) model is introduced and simulated. The introduced DSM model is based on the concept of capping consumers’ monthly energy consumption and rewarding consumers who do not exceed this cap with energy tradeable credits that can be traded using blockchain-based Peer-to-Peer (P2P) energy trading. A model based on 200 households is used to simulate the proposed DSM model and prove that this model can be beneficial to both energy companies and consumers.

On Modeling the Combustion of a Single Micron-Sized Aluminum Particle with the Effect of Oxide Cap.

The formation of oxide cap, which results from the condensation of gaseous aluminum oxide, makes a non-negligible impact on the combustion process of micron-sized aluminum particles, but its growth and effect are still unknown. Also, the transition of combustion modes during the combustion process, which affects the growth rate of the oxide cap, needs to be explored. Therefore, a detailed combustion model of a single micron-sized aluminum particle is developed to predict the transition of combustion modes and the effect of the oxide cap. This combustion model consists of a vapor-phase kinetic model and a particle model coupled by the Strang splitting algorithm. The predicted ignition delay and combustion times are compared with experimental data to validate the combustion model. Three combustion modes including vapor-phase, transitional, and surface combustions are considered in this combustion model. We find that the two modes coexist for particles between 100 and 200 μm when the ambient temperature and pressure are 2500 K and 1 atm, respectively. A higher ambient temperature extends the transition of combustion mode toward smaller sizes. An oxide cap model considering surface free energy is proposed to study the growth and effect of the oxide cap on the combustion process of micron-sized aluminum particles. We find that the formation of oxide cap limits the evaporation rate of aluminum directly due to the reduced active surface area. The oxide cap stabilizes the evolution of particle temperature and determines the burning time. The predicted burning time is reduced by a factor of 2 at least considering the growth of oxide cap.

One- and two-dimensional finite element modelling of thaw consolidation

Coupled thermo-hydro-mechanical finite element (FE) modelling of thaw consolidation is presented. One-dimensional FE analyses are performed for thaw consolidation of a soil column due to self-weight and with a combination of self-weight and surcharge, with the linear and nonlinear void ratio – effective stress – hydraulic conductivity relationships of thawed soil. The nonlinear behaviour of thawed soil is modelled using a modified Drucker–Prager cap model, while the hydraulic conductivity is varied with the void ratio. Finally, two-dimensional FE modelling of thaw consolidation around a warm pipeline buried in permafrost is performed. The rapid reduction of the void ratio with consolidation, especially at the low-stress level, results in a wide variation of hydraulic conductivity within the thawed zone. The significantly large hydraulic conductivity of soil elements along the curved thaw front, as compared to that of thaw consolidated soil, causes the flow of water along the thaw front, instead of a vertical flow, as assumed in previous 1D thaw consolidation modelling of buried pipelines.

Building Structure Analysis With and Without Direct Foundation Modelling using Reinforced Concrete Special Moment Resisting Frame

The modelling of placement upon the seismic resistant structure can be carried out separately or directly. Separated modelling refers to the modelling using fixed joint, while direct modelling is defined as the lower structure directly using spring on soil-foundation interaction. Both modelling have differences in the context of behaviour and reaction of structure that must be adjusted based on SNI 1726:2019 and pile needs. This research analysed the calculation of static bearing capacity of pile and manual calculation of k coefficient by Nakazawa method and a supporting program SAP2000 V14.2.5. The analysis results indicated that under the manual calculation, total pile needs on fixed joint modelling of spun pile in diameter 600 mm class B are 185 piles within pile cap modelling at every point of column, meanwhile using SAP2000 V14.2.5, it is obtained the pile needs of spring modelling are 176 piles within integral pile cap modelling. The structural behaviour and the reaction of both modelling demonstrated the values of drift control, period, mass participation, static dynamic shear force, and force output in the fixed joint modelling were less than spring modelling.

The influence of small-scale magnetic field on the heating of J0250+5854 polar cap

The influence of surface small-scale magnetic field on the heating of PSR J0250+5854 polar cap is considered. It is assumed that the polar cap is heated only by reverse positrons accelerated in pulsar diode. It is supposed that pulsar diode is located near the star surface (polar cap model) and operates in the steady state space charge-limited flow regime. The reverse positron current is calculated in the framework of two models: rapid and gradually screening. To calculate the production rate of electron-positron pairs we take into account only the curvature radiation of primary electrons and its absorption in magnetic field. It is assumed that some fraction of electron-positron pairs may be created in bound state that can later be photoionized by thermal photons from star surface.

Modelling powder compaction with consideration of a deep grooved punch

In this work a modelling approach for predicting density distribution in the vicinity of two facing grooves on a parallelepiped compact surface, is developed and results are validated using X-ray tomography. An experimental hybrid procedure is proposed to calibrate Drucker-Prager Cap model material parameters which are numerically validated and considered for FEM compaction simulation of grooved specimen using Arbitrary Lagrangian Eulerian method (ALE). Results of the predicted density show high values under the groove and low values on its flanks and shoulders. Similar findings were observed in the literature. Additionally, a strong density gradient between the facing grooves is predicted and validated, demonstrating that the calibrated model achieved good agreements with the measurements.The proposed hybrid calibration procedure could be used for other shape and size die not benefiting from radial instrumentation. Moreover, the ALE approach demonstrated its robustness in solving die powder compaction in presence of strong mesh distortions.

Young radio-loud gamma-ray pulsar light curve fitting

Context. Since the launch of the Fermi gamma-ray telescope, several hundred radio-loud gamma-ray pulsars have been detected, many belonging to millisecond pulsars but some belonging to the young pulsar population with spin periods longer than 30 ms. Aims. Observing simultaneously pulsed radio and gamma-ray emission from these stars helps to constrain the geometry and radiation mechanisms within their magnetosphere and to localize the multiple photon production sites. In this paper we fit the time-aligned gamma-ray light curves of young radio-loud gamma-ray pulsars. We assume a dipole force-free magnetosphere where radio photons emanate from high altitudes above the polar caps and gamma rays originate from outside the light cylinder, within the striped wind current sheet. Methods. We computed a full atlas of radio and gamma-ray pulse profiles depending on the magnetic axis obliquity and line-of-sight inclination with respect to the neutron star rotation axis. By applying a χ2 fitting technique, we were able to pin down accurately the magnetosphere geometry. Further constraints were obtained from radio polarization measurement following the rotating vector model, including aberration and retardation effects. Results. We find a good agreement between our model and the time-aligned single- or double-peaked gamma-ray pulsar observations. We deduce the magnetic inclination angle and the observer line of sight with respect to the rotation axis within a small error bar. The distinction between radio-loud or radio-quiet gamma-ray pulsars or only radio pulsars can entirely be related to the geometry of the associated emitting regions. Conclusions. The high-altitude polar cap model combined with the striped wind represents a minimalistic approach able to reproduce a wealth of gamma-ray pulse profiles for young radio pulsars. Based on self-consistent force-free simulations, it gives a full geometrical picture of the emission properties without resorting to detailed knowledge of the individual particle dynamics and energetics.

Real options analysis of revenue risk sharing in post-disaster housing reconstruction

PurposePost-disaster housing reconstruction (PDHR) demands a considerable percentage of global property investment, yet the post-disaster environment presents intricate challenges to reconstruction financing for governments and at the same time, revenue uncertainty for private investors. The purpose of this study is to develop a methodology for tackling land shortage and the financial challenges of PDHR in the aftermath of a disaster.Design/methodology/approachThis study developed a methodology based on a combined minimum revenue guarantee and maximum revenue cap model using a well-established real options analysis (ROA) for revenue risk sharing in PDHR projects and land readjustment (LR) for finance. The applicability of the purported model is demonstrated through an illustrative example.FindingsThe results show that flexibility in the options could increase the PDHR contractor’s risk profile by increasing the expected value of the contractor investment and reducing the probability of investment loss. On the other side, a cap on the contractor revenue stream would allow the government to benefit from any excess in revenue and would counterbalance the value of the option.Practical implicationsThe framework proposed in this study could serve as a practical risk-revenue sharing in PDHR projects. Governments and policymakers could use the findings to enable the successful delivery of PDHR projects and consequently bring the quality of life of affected people to pre-disaster conditions.Originality/valueThis study can be considered as a first attempt toward the use of the Australian barrier style options structure, and the trinomial lattice valuation model in PDHR projects, which incorporates LR, public-private partnerships, governmental guarantees and PDHR concepts in one ROA-based framework.

Comparison of Different Procedures for Progressive Collapse Analysis of RC Flat Slab Structures under Corner Column Loss Scenario

Progressive collapse is the failure of the whole structure caused by local damage, which leads to significant economic and human losses. Therefore, structures should be designed to sustain local failures and resist subsequent nonproportional damage. This paper compared four procedures for a progressive collapse analysis of two RC structures subjected to a corner column loss scenario. The study is mainly based on the methods outlined in the current Russian standard (linear static (LS) pulldown, nonlinear static (ND) pulldown, and nonlinear dynamic), but also includes LS and NS pushdown procedures suggested by the American guidelines and linear dynamic procedure. We developed detailed finite element models for ANSYS Mechanical and ANSYS/LS-DYNA simulations, explicitly including concrete and reinforcement elements. We applied the Continuous Surface Cap Model (MAT_CSCM) to account for the physical nonlinearity of concrete. We also validated results obtained following these procedures against known experimental data. Simulations using linear static pulldown and linear dynamic procedures lead to 50–70% lower results than the experimental because they do not account for the nonlinear behavior of concrete and reinforcement. Displacements obtained from the NS pulldown method exceed the test data by 10–400%. It is found that correct results for both RC structures can only be found using a nonlinear dynamic procedure, and the mismatch with the test data do not exceed 7%. Compared to static pulldown methods, LS and NS pushdown methods are more accurate and differ from the experiment by 28% and 14%, respectively. This relative accuracy is provided by more correct load multipliers depending on the structure type.