Transfer Method Research Articles

A FEM/DEM adaptive remeshing strategy for brittle elastic failure initiation and propagation

AbstractThis article presents an adaptive remeshing strategy between the finite element method (FEM) and the discrete element method (DEM). To achieve this strategy, an edge‐to‐edge coupling method based on Lagrange multipliers has been set‐up to ensure the continuity of velocities at the interface. To switch from a computation initially purely FEM to a FEM‐DEM one, a field transfer method was required. In particular, a displacement field transfer method has been set‐up. The switching from a FEM subdomain to a DEM one is activated by a transition criterion. Each time a FEM subdomain is substituted by a DEM one, the DEM subdomain microscopic properties are set‐up with respect to the subdomain geometry and desired particle refinement. This is performed thanks to the linking to the so‐called “Cooker,” a tool distributed along with the GranOO Workbench. Two subdomain remeshing cases were dealt with: that of an initially FEM subdomain that is converted to DEM, and that of DEM subdomains which coalesce. A numerical test case shows that the dynamic remeshing method behaves as expected: FEM subdomains are substituted by DEM ones when the transition criterion is met, and DEM subdomains coalesce when required. The final numerical test case shows a good agreement with a crack propagation experiment of the literature, while a speedup of about 20 was observed when compared to pure DEM computation.

Impact of land use evolution on the value of ecosystem services in the returned farmland area of the Loess Plateau in northern Shaanxi

The Grain-for-Green Program (GGP) has been contributing to changes in the nationwide use of land and vegetation, further changing ecosystem services (ESs). However, the influence of GGP on ESs, in terms of land use evolution remains elusive. This study is conducted based on a dataset collected every five years for the past 30 years. This dataset includes land use statistics and is obtained from Landsat images and the random forest algorithm. Land use evolution in the Loess Plateau in northern Shaanxi from 1990 to 2020 is systematically analyzed. The interest transfer method is adopted to compute the ecosystem service value (ESV), and the willingness and economic affordability are included in the evaluation model. Finally, a cross-sensitivity coefficient is specified to reveal the effects of land use evolution on the ESV in the studied area. The results are as follows: (1) Land use changes mainly occurred on farmland, forest, and orchards. In the past 30 years, the area of cultivated land showed a decreasing trend, whereas the land areas used for other purposes increased. (2) In the same period, the ESV of the investigated plateau continued to rise, increasing by 5.12 billion USD in total. Additionally, the ESV provided by secondary services increases in the following order: regulating services > supporting services > provisioning services > cultural services. (3) The cross-sensitivity coefficient showed that the net transition among forest, grassland, orchard, and unused land in the studied region is relatively sensitive, and a larger transition span of land utilization leads to a stronger effect on the ESV. This study offers crucial data for the compensation of interregional ecology and provides model cases for other regions for ecosystem management.

Numerical evaluation of scaffolds as a method to restore continuity of a long bone

PurposeIn case of necessity of removing a bone fragment, the process of restoring bone continuity relies on the use of bone grafts or bone plates as osteosynthesis methods. These approaches are characterised by several disadvantages, such as significant changes in load transfer method through the bone. Recently, scaffolds emerged as potentially more efficient method in restoring bone continuity. In this paper, an attempt was made to validate the correctness of this statement. Materials and methodsThree lengths of bone defects were selected for the analysis: 35, 45 and 55 mm, located in the lower, middle and upper section of femur diaphysis. The following methods of restoring bone continuity were evaluated: 1 plate, 2 parallel plates, 1 plate and scaffold, 2 parallel plates and scaffold. Simulations of the forces generated during human gait cycle were performed. The evaluated parameters obtained were: maximal and average stresses, strain energy density as well as percentage changes in values of these parameters in relation to the values obtained for intact bone in its selected zones. ResultsStudies have shown that the best method of restoring bone continuity is to use a single plate with a scaffold. The stress distribution obtained by this method had the highest similarities to the one obtained for intact bone model in terms of load transfer as well as maximal stresses values obtained. ConclusionsThe study validated the statement that the use of a scaffold to restore bone continuity is potentially more efficient method than conventional approaches.

Wetland Changes and Ecosystem Services Valuation of Kapla Beel in Assam

Background: Wetlands are productive ecosystem with immense potentiality of providing various goods and services. But they are fast depleting due to various natural and anthropogenic causes. Kapla beel is a freshwater wetland located in Barpeta district in the lower Brahmaputra valley of Assam. Area of the Kapla beel has been decreasing over the years. This study shall make an attempt to analyse the causes of land use and land cover changes of Kapla beel of Assam and assess its ecosystem services value changes during the period 1990 to 2022. Methods: To assess the changes, two Landsat images for the year 1990 and 2022 of Kapla beel were taken from the United State Geological Survey (USGS) Earth Explorer. Land-use change analysis was assessed by comparing the areas occupied by each land use in each period using the ArcGIS software. The dynamicity index is used to calculate the rate of change in land cover. In order to assess the changes in the wetland ecosystem service value due to wetland changes, Benefit Transfer Method is used which involves transferring monetary values of ecosystem services from previous studies. Result: The valuation of ecosystem services underlines the fact that wetlands are highly productive and economically viable ecosystems. Accounting of ecosystem services provides information about the need for optimal decision -making towards judicious use of wetland resources for their sustenance.

Strategy for transferring van der Waals materials and heterostructures

Two-dimensional (2D) layered materials and heterostructures have garnered significant attention for their exploration of uncharted scientific phenomena and their versatile applications. The customization of van der Waals heterostructures heavily relies on their transfer assembly techniques. While traditional dry or wet transfer methods show promise in manipulating 2D materials and heterostructures, challenges such as residues from supporting layers, incomplete substrate etching, embedded bubbles at interfaces, and transfer-induced damages like cracks and wrinkles still pose significant hurdles. In this review, we comprehensively examine the state of transfer technology, identifying the origins of these technical challenges and discussing potential solutions. We specifically focus on strategies developed within the last 3–5 years that aim to address these complex transfer issues, facilitating the integration of 2D materials and heterostructures into existing silicon-based technologies. Finally, we offer perspectives to guide the optimization of each transfer method and inspire future industrial applications of 2D materials.

Review on convective and radiation heat transfer between bridges and external environments

The heat exchange between bridges and external environments is the primary cause of the temperature effect on bridges. The complexity of the two-phase (gas–solid) heat transfer mechanism, the diversity of the surface characteristics of bridge materials, and the uncertainties of the environment in which bridges are located make the numerical calculation of the heat exchange between bridges and external environments difficult. Several studies have been conducted by scholars around the world. In this work, the research on convective and radiative heat exchange between bridges and external environments is surveyed, analyzed, and summarized. The influencing factors and calculation methods of bridge temperature are examined, and the convective heat transfer and radiation mechanisms, theoretical calculations, and experimental measurement methods used to investigate the relation between bridges and external environments are summarized and analyzed. The value determination methods for convective heat transfer and radiation absorption coefficients in the calculation of the bridge temperature field are summarized. In addition, the problems and shortcomings of current research are evaluated, and future research directions are identified and discussed.

Impacts of land use and cover changes on ecosystem service values from 1992 to 2052 in Gena District, Southwest Ethiopia

Land use and cover changes alter the functions and structures of ecosystem, resulting in variations in Ecosystem Service Values (ESVs). Thus, we examined the impacts of land use/land cover (LULC) changes on ESVs from 1992 to 2052 using geospatial technologies. The Landsat images were classified using the supervised maximum likelihood classification technique, and future changes in LULC were predicted using the CA-Markov model. Ecosystem Service Values coefficients were adopted from empirical studies and ESVs changes were evaluated based on the benefit transfer method using LULC data for the study periods, with their corresponding modified ESVs coefficients. The results revealed that, the proportions of grassland, forestland and shrubland declined by 58.5 %, 48.15 % and 33.48 %, respectively, from 1992 to 2022. Simultaneously, the highest rate of expansions of waterbodies (34 times), farmland and settlement threefold as well as bareland (60.2 %) from 1992 to 2022 was noticed. As a result, decreasing trends were experienced in the total ESVs of the district from US$33.6 million in 1992 to US$27.79 million in 2022, and are anticipated to further decline to US$25.94 million in 2052. The ESVs of forestland, shrubland and grassland shrank from 53.1 %, 40 % and 2.78 % in 1992 to 33.28 %, 33.16 % and 1.4 % in 2022 these changes are anticipated to continue for the next three decades, except trend for the increase in grassland ecosystem service value. Therefore, the government should redesign effective land management strategies to alleviate the negative consequences of LULC changes, facilitate payment for ecosystem services, and design ecotourism to boost the income of residents for major land use management-based production systems to increase the ESV in the district.

Hybrid knowledge transfer for MARL based on action advising and experience sharing.

Multiagent Reinforcement Learning (MARL) has been well adopted due to its exceptional ability to solve multiagent decision-making problems. To further enhance learning efficiency, knowledge transfer algorithms have been developed, among which experience-sharing-based and action-advising-based transfer strategies share the mainstream. However, it is notable that, although there exist many successful applications of both strategies, they are not flawless. For the long-developed action-advising-based methods (namely KT-AA, short for knowledge transfer based on action advising), their data efficiency and scalability are not satisfactory. As for the newly proposed experience-sharing-based knowledge transfer methods (KT-ES), although the shortcomings of KT-AA have been partially overcome, they are incompetent to correct specific bad decisions in the later learning stage. To leverage the superiority of both KT-AA and KT-ES, this study proposes KT-Hybrid, a hybrid knowledge transfer approach. In the early learning phase, KT-ES methods are employed, expecting better data efficiency from KT-ES to enhance the policy to a basic level as soon as possible. Later, we focus on correcting specific errors made by the basic policy, trying to use KT-AA methods to further improve the performance. Simulations demonstrate that the proposed KT-Hybrid outperforms well-received action-advising- and experience-sharing-based methods.

Analysis of the heterojunction band offset of h-BN/TMDCs

In order to analyze the effect of the chalcogen on the band alignment of the Transition metal dichalcogenides (TMDCs) and hexagonal Boron Nitride (h-BN) heterojunction, we fabricated the h-BN/TMDCs heterojunction by vertically stacking mono-layer h-BN and multi-layer TMDCs by the wet transfer method. The four heterojunctions are h-BN/WS2, h-BN/WSe2, h-BN/MoS2 and h-BN/MoSe2. X-ray photoelectron spectroscopy (XPS) has been employed to ascertain the Valence Band Offset (VBO) at the junctions created among these heterojunctions. All heterojunction band alignment styles are type-I. When the chalcogen changes from S to Se, the heterojunction VBO values increase. Specifically, in case of h-BN/WS2 and h-BN/WSe2 the VBO is 2.42 eV and 2.81 eV, respectively, and the magnitude of the difference is 0.39 eV. In the same case for h-BN/MoS2 and h-BN/MoSe2 the VBO is 2.52 eV and 2.55 eV, respectively, and the magnitude of the difference is 0.03 eV. The aforementioned research has obtained the band alignment for four heterojunctions, which provides a valuable reference for the design and analysis of the correlation devices in the future.

Correlation between Morphology, Mechanics, and Electricity of PEDOT:PSS-Based Stretchable Electrodes Fabricated by the Prestrain Transfer Method

Correlation between Morphology, Mechanics, and Electricity of PEDOT:PSS-Based Stretchable Electrodes Fabricated by the Prestrain Transfer Method

Simplified method and numerical simulation analysis of pipe-group long-term heat transfer in deep-ground heat exchangers

Deep-buried pipe-group heat transfer is a primary form of utilizing geothermal energy in the middle and deep ground layers. This study introduces a methodology to simplify the heat transfer process of a pipe-group into a single borehole within a finite computational domain. The proposed methodology allows for rapid and accurate assessment of the heat transfer performance of the pipe-group with coaxial deep-ground heat exchangers (C-DGHEs). The feasibility of this simplified method is supported by numerical validation. Consequently, a 20-year numerical computation is performed for pipe-group models with spacings of 15, 20, 30, and 40 m, alongside a comparative study on the heat transfer of a single borehole C-DGHE with a computational domain radius of 200 m. For a pipe-group spacing of 15 m, the results demonstrated that the heat transfer boundary is exceeded in the first year of heat extraction but stabilized into a steady decline. For a spacing of 40 m, the decrease in heat transfer over 20 years was less than 15 % compared to the single C-DGHE. This research effectively evaluates the heat transfer performance of pipe groups, providing theoretical support and technical guidance to develop and promote the applications of deep geothermal energy.

Temperature Field Characteristics of Limited Slip Clutch under Various Condition Parameters

The temperature field of limited slip clutch (LSC) seriously interferes with torque transmission. In this paper, the attribute of dynamic partition of slip heat flux is considered. A calculation model of temperature field is also established by combining the proposed new method of fluid-solid equivalent convective heat transfer. The simulation and experiment of different relative speed, lubricant flow, and temperature are carried out. Furthermore, the comprehensive evaluation index of average temperature growth ratio and maximum radial temperature difference is proposed. The results show that the deviations of temperature rising rate and average temperature are not more than 0.2 °C/s and 6 °C, respectively. Heat flux partition value of separator plate increases approximately proportionally with relative speed. Changing relative speed from 40 r/min to 80 r/min, average temperature growth rate and maximum radial temperature difference of separator plate increase by 0.35 °C/s and 2.08 °C, respectively. On the contrary, increasing lubricant flow or reducing lubricant temperature weakens actual heat flux input of clutch. From 3 L/min to 10.5 L/min about lubricant flow, the average temperature growth rate and maximum radial temperature difference caused by higher relative speed are reduced by 0.32 and 2.71 °C, respectively. However, when lubricant temperature is adjusted from 65 °C to 30 °C, average temperature growth rate is reduced by 0.51 and the variation of maximum radial temperature difference does not exceed 0.32 °C. The research can accurately simulate actual energy flow at friction pair interface and assist in exploring the influence of condition parameters on temperature field.

Transparent, low dark current, fast response ultraviolet and short-wavelength blue photons photodetector based on Graphene/SrTiO3 single crystal

Ultraviolet light and short-wavelength blue photons (UV-SWB) can cause damage to the human body under excessive exposure. Strontium titanate (SrTiO3), which is a crucial perovskite oxide with a direct energy band gap of ∼3.2 eV, has great potential for UV-SWB photodetection. In this work, UV-SWB photodetector with high transparency based on Graphene/SrTiO3 heterojunction was fabricated by graphene transfer method. The Graphene/SrTiO3 photodetector exhibits an ultra-low dark current of 6 pA at a 30 V bias. The response spectrum of the Graphene/SrTiO3 photodetector was 220–410 nm, covering the UV-SWB band. Under 385 nm light irradiation, the photodetector exhibits a response of 3.4 mA/W, a detectivity of 1.5 × 1010 Jones, a response time of 186 ms, and a light-to-dark current ratio of 103 magnitude at a 30 V bias. In addition, the transmittance of the photodetector in the visible light band reaches 80 %, which has excellent visualization performance. The excellent performance of Graphene/SrTiO3 photodetector is attributed to the high crystal quality of SrTiO3 wafer and the van der Waals interface constructed by Graphene/SrTiO3 reduces the bulk defect density and interfacial state density, which could be beneficial the separation and transport of photogenerated carriers in the active layer and heterojunction. This study has important reference value for the design and manufacture of UV-SWB photodetectors.

Atomistic to continuum mechanics description of crystal defects with dislocation density fields: Application to dislocations and grain boundaries

The atomic structure of crystal defects such as dislocations, grain or phase boundaries, control these defects’ properties: their mobility, ability to cross-slip, or solute segregation. These crystal defects can be conveniently studied by atomistic simulations and one then needs to transfer relevant information at the upper scale to model microstructures containing a large number of defects, e.g., a polycrystal. Here, we propose an atomistic to continuum mechanics crossover method that (i) represents the atomic structure of dislocations cores by an appropriate Nye dislocation density tensor field and (ii), captures quantitatively the short and long range mechanical fields of defects. For (i), we propose a modified and improved interpolation method based on the original work by Hartley and Mishin. For (ii), we use a field dislocation mechanics framework that rigorously calculates/evaluates the mechanical fields associated with any Nye dislocation density distribution. The transfer method relies on molecular static calculations using two energetic models — ab-initio for screw dislocation core simulations in tungsten, and EAM potential for low and large angle grain boundaries in copper. Our findings demonstrate the effectiveness of the proposed approach in reconstructing the Burgers vector, and continuous strain and rotation fields. The framework is further applied to analyze the elastic interactions between extrinsic edge dislocations and a low angle grain boundary in copper.

Multiresponsive Behavior of the Pickering Emulsifier and Its Application for Collecting Small Oil Droplets in Water.

Responsive Pickering emulsions, with unique nanoparticle interfaces and sensitivity to external stimuli, significantly enhanced the stability and applicability of Pickering emulsions. Multifunctional composite material poly((2-(dimethylaminoethyl methacrylate)-b-(acrylate cyclodextrin))/Fe3O4 nanoparticles, namely P(DMAEMA-b-A-CD)/Fe3O4, with both multiresponsive characteristics and emulsifying capabilities had been designed to remove small oil droplets from water. Using the reversible addition-fragmentation chain transfer (RAFT) method, diblock polymers P(DMAEMA-b-A-CD) were grown in a controlled manner on the surface of Fe3O4. The Fe3O4 core showed responsiveness to a magnetic field, and the block copolymers prepared via the RAFT method demonstrated reactivity to both pH and CO2. The P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles exhibited the capability to form Pickering/Oxford emulsions with exceptional stabilization properties. It could be observed that the introduction of CO2, acid, and a magnetic field led to the breakage of the emulsion, while the emulsion could be restabilized by removing the CO2 and the magnetic field or by adding alkali. Measurements of interfacial tension, ζ-potential, and contact angle demonstrated that the emulsification/breakdown mechanisms associated with pH and CO2/N2 were related to the surface wettability of the nanoparticles. In addition, the emulsifier had an excellent cycling capacity with at least 10 cycles by CO2/N2. Additionally, P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles exhibited excellent stability in oil phases with large polarity differences and various real oil phases with different viscosities. Importantly, the P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles could serve as functional materials for efficiently separating small oil droplets from water through the application of a magnetic field. Therefore, P(DMAEMA-b-A-CD)/Fe3O4 nanoparticles held promising potential as materials with economic and commercial value for oil-water separation applications.

Wireless Power Transfer Efficiency Optimization Tracking Method Based on Full Current Mode Impedance Matching.

Wireless power transfer (WPT) technology is a contactless wireless energy transfer method with wide-ranging applications in fields such as smart homes, the Internet of Things (IoT), and electric vehicles. Achieving optimal efficiency in wireless power transfer systems has been a key research focus. In this paper, we propose a tracking method based on full current mode impedance matching for optimizing wireless power transfer efficiency. This method enables efficiency tracking in WPT systems and seamless switching between continuous conduction mode and discontinuous mode, expanding the detection capabilities of the wireless power transfer system. MATLAB was used to simulate the proposed method and validate its feasibility and effectiveness. Based on the simulation results, the proposed method ensures optimal efficiency tracking in wireless power transfer systems while extending detection capabilities, offering practical value and potential for widespread applications.

Unstructured Conservative Level-Set (UCLS) method for reactive mass transfer in bubble swarms at high density ratio

This research presents a parallel Unstructured Conservative Level-Set (UCLS) method for reactive mass transfer in bubbles with a high-density ratio. This method uses the multiple-marker UCLS approach to circumvent the numerical coalescence of bubbles, combined with the finite-volume method to discretize transport equations on 3D collocated unstructured meshes. The fractional-step projection method solves the pressure-velocity coupling. The central difference scheme discretizes the diffusive term, whereas convective term within the momentum transport equation, level-set advection equations, and mass transfer equation are discretized by unstructured flux-limiters schemes. Such a combination of numerical techniques preserves the numerical stability in bubbly flows with a high Reynolds number and high-density ratio. Numerical and physical findings on the effect of physical properties ratios on the reactive mass transfer are reported, including their effect on the Reynolds number, interfacial area and Sherwood number.

Age-Related Increase in Live-Birth Rates of First Frozen Thaw Embryo Compared With First Fresh Transfer in Initial Assisted Reproductive Technology Cycles Without Preimplantation Genetic Testing [ID 2683417

INTRODUCTION: Compare live-birth outcomes stratified by age between primary frozen (FET) and fresh transfers in initial autologous assisted reproductive technology (ART) cycles without preimplantation genetic testing (PGT). METHODS: This was a retrospective cohort study of autologous first ART cycles without PGT comparing success rates of primary embryo transfer (frozen thaw versus fresh) from the 2014–2020 SARTCORS database. We compared live-birth rate (LBR) stratified by age and cumulative live-birth rate (CLBR) for first FET versus first fresh cycles in first ART cycle. Primary transfer (FET or fresh) was the first transfer for an index retrieval. LBR was number of live births from first embryo transfer associated with first retrieval. CLBR was defined as at least one live birth from all linked embryo transfers within 1 year from initial retrieval. Multivariate logistic regression (MLR) determined association between live-birth outcomes and method of transfer. RESULTS: 228,171 first ART cycles resulted in primary embryo transfer. 62,100 initial FETs and 166,071 fresh transfers were compared. LBR was 48.3% for initial FETs versus 39.8% for initial fresh transfers (P<.001). CLBR was 71.8% for initial FETs versus 59.2% for initial fresh transfers (P<.001). MLR demonstrated that initial FETs had a greater chance of live birth across all age groups, with adjusted odds ratio of live birth incrementally increasing with advancing age groups. CONCLUSION: Overall, LBR and CLBR were greater for first FET than fresh transfers with incremental increases in odds of live birth with advancing age, suggesting the presence of a more favorable age-related change in endometrial receptivity present in frozen–thawed cycles.

Simulation test platform for the controlled storage and transfer of liquid hydrogen

Clean-energy propulsion machines, including trucks, tractors, ships, and aircraft, for heavy-duty and long-range mobility have moved, by necessity, to onboard liquid hydrogen (LH2). However, the established method of storage and transfer is problematic due to losses and for any duty-cycle of a sporadic or on/off nature. Integral servicing system methodology is needed for both safety and cost effectiveness in the key drivers of time savings, product savings, and venting exposures. Modern controlled storage technology enables quick and effective vehicle servicing at the point of use. Simulations of controlled storage/transfer (CS/T) methodologies are performed using a multi-purpose LH2 simulation test platform comprised of two primary systems: Cryostat CS900 tank and transfer system and the LS20 liquefaction/refrigeration and storage system. Testing includes both steady-state and transient modes of operation to demonstrate both zero boiloff (ZBO) and zero-loss transfer (ZLT) modes. Technical areas of use include product development for tanks, refrigeration, transfer systems (lines, dispensers, pumps, valves); experimental validation of analytical models and thermofluidic properties; thermal insulation performance test data under relevant conditions; thermophysical characterization of materials and structures; instrumentation and sensors development; tank boiloff and heat flux engineering design data. Descriptions and preliminary test results are given along with thermal performance analyses from real-world testing and experimentation.

Evaluation of the effects of various fan parameters on the cooking process in commercial cooking ovens

Commercial kitchen ovens are utilized in various capacities and models within commercial enterprises, operating on either electric or gas power. Numerous parameters affect the cooking process. Particularly, for effective cooking in an oven, it’s crucial to evenly distribute airflow over the food. Correct airflow significantly impacts the cooking process. Considering the differences in processing requirements based on the characteristics and quantity of the food (such as temperature, humidity, fan speed, duration, etc.), the method of heat transfer should be primarily assessed. Non-uniform distribution of hot air during the cooking process leads to varied cooking qualities among trays within the oven. Therefore, in achieving effective cooking, factors like oven cavity, number of trays, fan geometry, fan rotation speed, direction, movement intervals, and the turbulent airflow generated by the fan in the cooking chamber need thorough examination. This study analyzed simulation data evaluating the effects of different fan geometries, fan rotation directions, and timing on heat transfer in a prototype electric commercial cooking oven using gastronomic GN-1/1 sized with 10 trays. Additionally, comparison of test and design validation data in the specially developed prototype cooking oven was conducted. Assessments were made with different fan movements (fan diameters, rotation direction, speed etc.) and a fan protection plate in front of the oven to achieve more efficient heat distribution on the food. Depending on various fan parameters, this study contributed to reducing energy consumption in the prototype commercial cooking oven.