Three-dimensional Computational Model Research Articles

Perspectives of online anatomy teachers: A neglected study population struggles with the invisible student.

Online teachers are an under-researched population, but their perspectives are crucial to the successful implementation of online education. A fully online section of an established face-to-face (F2F) two-semester undergraduate anatomy course with a prosection laboratory commenced in 2012 at The University of Western Ontario, Canada. Professors' lectures for F2F students were broadcast in live and archived format to online students using Blackboard Collaborate (BBC) video conferencing software. Teaching assistants (TAs) delivered online laboratories using BBC and three-dimensional (3D) anatomical computer models. This study explored the common experiences and issues faced by the course teachers from 2012 to 2014. Transcripts from open-ended, individual interviews with professors (n=4) and TAs (n=5) were coded and analyzed thematically. The teachers' concern for their inability to see the students during sessions to assess class engagement and their teaching effectiveness, and to develop social relationships, was the main finding. However, video conferencing software and email were sufficient communication methods for the students' questions and the teachers' answers. The TAs noted usability challenges and anatomical inaccuracies in the 3D models compared to cadavers. Due to limitations of BBC's screen sharing function, live manipulation for the 3D computer models was not possible; however, the TAs found pedagogical value in using screen captures of the models for drawing activities with the students. Overall, preparation time for teaching online was longer than for F2F. The study's findings provide science educators with issues to consider when preparing for online teaching and recommendations to optimize the teaching experience.

Fat Quantification Imaging and Biophysical Modeling for Patient-Specific Forecasting of Microwave Ablation Therapy.

Computational tools are beginning to enable patient-specific surgical planning to localize and prescribe thermal dosing for liver cancer ablation therapy. Tissue-specific factors (e.g., tissue perfusion, material properties, disease state, etc.) have been found to affect ablative therapies, but current thermal dosing guidance practices do not account for these differences. Computational modeling of ablation procedures can integrate these sources of patient specificity to guide therapy planning and delivery. This paper establishes an imaging-data-driven framework for patient-specific biophysical modeling to predict ablation extents in livers with varying fat content in the context of microwave ablation (MWA) therapy. Patient anatomic scans were segmented to develop customized three-dimensional computational biophysical models and mDIXON fat-quantification images were acquired and analyzed to establish fat content and determine biophysical properties. Simulated patient-specific microwave ablations of tumor and healthy tissue were performed at four levels of fatty liver disease. Ablation models with greater fat content demonstrated significantly larger treatment volumes compared to livers with less severe disease states. More specifically, the results indicated an eightfold larger difference in necrotic volumes with fatty livers vs. the effects from the presence of more conductive tumor tissue. Additionally, the evolution of necrotic volume formation as a function of the thermal dose was influenced by the presence of a tumor. Fat quantification imaging showed multi-valued spatially heterogeneous distributions of fat deposition, even within their respective disease classifications (e.g., low, mild, moderate, high-fat). Altogether, the results suggest that clinical fatty liver disease levels can affect MWA, and that fat-quantitative imaging data may improve patient specificity for this treatment modality.

Theoretical Modeling and Analysis of Blue Laser Characteristics of Continuous-Wave Single-Wavelength Two-Photon Pumped Rb-Vapor Laser

Based on an analysis of kinetic processes in the continuous-wave (CW) single-wavelength two-photon pumped Rb-vapor laser (Rb-TPAL), a three-dimensional computational model is established using the rate equation. Based on the application of the model to cavity-enhanced Rb-TPAL [Yuan <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Optics Express</i> 29, 4858 (2021)], the calculated and measured dependences of the laser power on the pump power show good agreement. We simulate the Rb-TPAL pumped by a high-power CW laser diode and analyze the effects of temperature, vapor cell length, pump waist, vapor cell transmission, and output mirror reflectance on the characteristics of the blue laser. The results suggest that the output power and efficiency of blue laser can be improved by optimizing the above parameters; however, the particles in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5^{2}\text{D}_{5/2}$ </tex-math></inline-formula> level face difficulty to transition to the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$6^{2}\text{P}_{3/2}$ </tex-math></inline-formula> level, and this limits the further improvement of blue laser efficiency; therefore, an approach is proposed to improve the efficiency of Rb-TPAL. This study can be useful for designing a two-photon pumped alkali metal laser with high-power output.

Investigation into thermo-mechanical reliability of copper trace lines in stacked dies ball grid array packaging

The persistent trend toward device miniaturization in the semi-conductor field has led to an ever finer line width and spacing of the copper trace patterns in the organic substrate used to connect the chip and printed circuit board. Thus, copper trace fracture has emerged as a major concern during the manufacturing process or subsequent thermal cycle reliability testing stage. Accordingly, the present study develops a three-dimensional (3D) computational model to analyze the reliability of the copper trace lines in a stacked ball grid array (BGA) containing two dies under thermal cycling between −65 °C and 150 °C. The simulation model takes account of both the tensile mechanical strength of the copper trace and its creep behavior at elevated temperatures. The validity of the simulation model is confirmed by comparing the predicted distribution of the plastic work density (PWD) in the copper trace/substrate layer following thermal cycling with the experimental observation. In general, the results show that the maximum average PWD of the copper trace should not exceed 400 kJ/m3 in order to minimize the risk of trace fracture. Taguchi analysis experiments are performed to determine the optimal design of the stacked BGA package which minimizes the PWD and hence maximizes the fatigue life of the copper trace. The results indicate that the thermo-mechanical reliability of the stacked BGA package depends mainly on the choice of substrate core material and core trace thickness.

Computational investigation of the hexagonal honeycomb adsorption reactor for cooling applications

Adsorption cooling is a sustainable technology, since it can utilize solar energy or waste heat, while employing substances without ozone depletion and global warming potential. The adsorption reactor design is determinant for the system performance. An underexplored geometry hitherto – the hexagonal honeycomb adsorption reactor – was numerically investigated. An in-house, validated, three-dimensional computational model based on unstructured meshes was employed. The Specific Cooling Power (SCP) and Coefficient of Performance (COP) were quantified for several geometrical and operational parameters. The cell inradius creates a dichotomy between SCP and COP, being 218.9 W/kg˙s and 0.356 for 1 mm, while being 80.4 W/kg˙s and 0.606 for 6 mm. The cell height influences prominently the SCP, being 159.5 W/kg˙s and 86.1 W/kg˙s for 5 mm and 30 mm, respectively. The fin thickness impacts mostly the COP, being 0.599 and 0.364 for 0.5 mm and 3 mm, respectively. Higher COP is achieved for higher evaporator, lower adsorption and lower condenser temperatures. Higher SCP is achieved for lower adsorption and condenser, and higher evaporator and desorption temperatures. Shorter cycles result in high SCP and low COP, whereas the inverse occurs for longer cycles. Aluminum heat exchanger yields 7.7% higher COP than copper. The results are discussed from a physical, as well as, an engineering perspective. • Hexagonal honeycomb reactor studied in the context of adsorption cooling. • Quantification of COP and SCP under various geometrical and operational parameters. • Geometrical and operational parameters are determinant for the reactor performance. • Adaptive cycle duration is highly useful for the regulation of system performance. • Aluminum heat exchanger yields 7.7% higher COP than copper.

Conjugate heat transfer analysis of molten salt in annular heater with rectangular wire coil

In this study, the detailed flow and heat transfer characteristics of molten salt for conjugate annular channel heater with rectangular wire coil were numerically investigated. Three-dimensional computational models are established based on the CFD software FLUENT, and are validated against the established empirical correlations. Good agreement is achieved within the considered range of Reynolds (Re = 673–1318). The effect of inner tube is evaluated and discussed based on numerical results. The simulated results show that radial velocity and tangential velocity are generated, and meanwhile two vortices are formed, as compared to the smooth annular channel heater. And The heat transfer is strengthened due to vortices. The distribution of local Nusselt number is not uniform, and hot spot zones are generated in the windward and leeward sides of rectangular wire coil, which are less than that of non-conjugate annular channel heater. This result revealed that the conjugate model must be established when considering the hot spot zone. Nu and f correlations are proposed to predict heat transfer and pressure drop for conjugate annular channel heater. Finally, the overall performance is evaluated based on the principle of entropy production, the value of which is in the range of 0.212–0.245.

A Robotic Arm Based Design Method for Modular Building in Cold Region

The robotic arm has emerged as an essential tool for the rapid construction of high-quality buildings due to its ability to repeat instructions, achieve precise positioning and fine operations. The robotic arm can also effectively replace workers to complete building construction under low temperature and short daylight conditions. Thus, it can be forward-looking to construct modular buildings in cold region, but how to realize the construction of modular buildings through human-machine coordination and remote operation is a significant issue. This article discusses the feasibility of robotic arm assembly design methods in the field of architecture by simulating the complete design and construction process of modular buildings. According to parameterized module design, a three-dimensional computer model is transformed into an electronic file that directs the action of the robotic arm to complete assembly via a custom processing program. This article details a theoretical and practical exploration of the construction of modular manipulators and has certain guiding significance for the intelligent design and construction of future buildings.

Micromechanical assessment of local failure mechanisms and early-stage ply crack formation in cross-ply laminates

Three-dimensional computational micromechanical models are developed to study local failure mechanisms and early-stage ply crack formation in a carbon fiber/epoxy [0/90/0] cross-ply laminate under tensile loading. Pressure-dependent inelastic deformation of the epoxy is captured by a user-defined material model, where brittle cavitation and ductile failure are considered local failure mechanisms. Manufacturing-induced defects, including nonuniform fiber spatial dispersion and resin pockets, are represented in the 90° ply. The effects of ply constraints on the local distortional and dilatational energy densities in the matrix are evaluated. Brittle cavitation is found to be the first and dominating failure mechanism, while local inelastic deformation indirectly influences the number and location of cavitation sites. Inelastic deformation is deemed necessary for predicting the linkage of the microcracks that are induced by brittle cavitation. The study provides important insight into the early-stage formation of ply cracks, which is essential for analyzing the subsequent ply crack formation.

Forced condensation heat transfer characteristics of vapour in the presence of noncondensable gas in horizontal tubes operating at high pressures

The forced condensation heat characteristics of vapour in the presence of noncondensable gas at high pressures are investigated. A three-dimensional computational model is proposed and the Lee condensation model is employed to simulate mass and energy transfer processes via interfaces. Numerical simulations are then performed to investigate flow and heat transfer characteristics of vapour in the presence of noncondensable gas at the operating pressure of 10 MPa. It is found that the buoyancy force influences the flow structure via the induced secondary circulation in a horizontal tube. The film thickness is increasing at the bottom wall, while the water film at the top wall first increases and then decreases downstream the tube due to gravity effects. Therefore, the heat transfer coefficient at the top wall is decreased along the tube due to reduced temperature difference. The decreasing heat transfer coefficient is also found at the bottom wall, however a roughly constant value is then attained downstream the tube. In addition, increasing the operating pressure attenuates the heat transfer performance of gas mixture. The work provides a new insight into flow and heat transfer characteristics of vapour in the presence of noncondensable gas in horizontal tubes at high pressures.

Fractography of Bone Using Reconstructed Computed Tomography (CT) Scans

Fractography has been shown to be applicable to forensic assessments of skeletal trauma by observing the presence and orientation of fracture surface features, which reveal information about the direction of crack propagation. Previous studies have examined dry or processed bone surfaces, often fractured under controlled experimental conditions. Here we assess a series of clinical computed tomography scans involving lower extremity injuries and find that a number of fracture surface features can be seen on three-dimensional computational models (surface and volumetric). These findings indicate that bone fractography can be used in skeletal trauma analyses without processing the remains and may also have clinical as well as forensic applications.

Insights from three-dimensional computational fluid dynamics modelling of a scroll vortex intake

ABSTRACT Scroll vortex intakes are commonly used in water supply, drainage and sewerage systems. Water flows into the intake via an eccentric approach channel, forming a swirling vortex flow with a stable air core along the dropshaft. Previous design theories have largely been based on unjustified assumptions on the velocity and pressure distributions of the vortex flow at the intake bellmouth. To clarify these assumptions, a validated three-dimensional computational fluid dynamics model has been developed. Model predictions compare well with independent measurements of flow profile, velocity and air core size. While the vortex flow in the scroll chamber can be described by a free vortex with constant circulation equal to that at the inlet, the tangential velocity and the pressure distribution at the bellmouth outlet have to be approximated by a forced vortex. A revised theory is proposed, providing significant improvement to the prediction of air core sizes and head–discharge relationship.

Numerical study on the mechanisms of storm geysers in a vertical riser-chamber system

In urban stormwater systems, a rapid increase in water inflow can cause the entrapment of air pockets and subsequent ejection of air/water mixture, commonly known as storm geysers. In this study, a three-dimensional computational fluid dynamics model was built based on a lab model, which consisted of an upstream pipe and a downstream pipe with different invert elevation (i.e. a drop), connected by a chamber with a riser on the top. The effects of the downstream pipe characteristics, location of the entrapped air pocket, and its volume on the pressure variation were examined. With the downstream pipe flowing in full, two mechanisms that possibly trigger geyser events were simulated and experimentally validated: (1) a rapid inflow front in the upstream pipe with the flow changing from free surface flow to pressurized flow, and (2) the air pocket releasing in a pressurized system. For the first mechanism, the pressure surge in the chamber was related to the capacity of the downstream pipe for the increased flow rate. For the second mechanism, a smaller air pocket in the upstream pipe can generate a higher pressure during the geyser event due to the reduced damping effect on the pressure variation. A larger pressure drop was observed for a larger volume of released air. Lower peak pressure was generated for an air pocket closer to the chamber due to the shorter duration for pressure to build up before the air pocket reached the chamber.

Investigation of optimal water utilization for water spray cooled photovoltaic panel: A three-dimensional computational study

The study focused on the development of a three-dimensional computational model for water spray cooling of photovoltaic panels. A water spray cooling technique can ensure performance improvement due to a reduction in panel operating temperatures due to its self-cleaning effect. The model was used to estimate the optimal amount of overall water utilization for cleaning and cooling. Excess water consumption affects power requirements for the pump and affects the overall cooling system performance. The model was also used to investigate the flow rate impact of water ejected from the nozzles onto the panel temperature profiles. The model was successfully validated with available experimental data of panel temperature at different flow rates. An average deviation of 1.4 K between the simulated and experimental data was well within permissible limits. The dependence of water spray volume fraction on heat transfer coefficients between the PV panel and water was also studied to understand the heat transfer characteristics. The optimum flow rate for the efficient operation of the system containing a photovoltaic panel and pump was 170 L/h. At 170 L/h, the electrical efficiency of the panel was 15.73%, panel power output was 40.25 W and the pump power required was 0.77 W. A maximum power output of 39.48 W for the system was achieved at a flow rate of 170 L/h.

Understanding Multi-Scale Battery Materials Degradation Via Three-Dimensional Imaging, Interface Analysis, and Computational Modeling

Understanding Multi-Scale Battery Materials Degradation Via Three-Dimensional Imaging, Interface Analysis, and Computational Modeling

Intervention of personalized ventilation on interpersonal airborne disease transmission

Personalized ventilation (PV) has been integrated to reduce the risk of interpersonal infection exposure in the office environment. Some studies showed that PV systems may increase occupants’ risk of airborne infection. Therefore, the aim of this study is to investigate the intervention of PV on interpersonal airborne disease transmission in office environment. A three-dimensional computational fluid dynamics model (CFD) was developed and experimentally validated in a clean chamber. Then the validated CFD model was used to calculate the diffusion of exhaled droplets under different particle size. Results showed at the size of 0.7μm particles, compared to pure mixing ventilation, the personal ventilation of 6L/s reduced the inhalation fraction （IF）from 0.121% to 0.092%，and the reduction ratio of IF is 23.96%. As of 5μm, the IF also decreased from 0.165% to 0.102%, and the reduction ratio of IF is 38.18%. The percentage of 50μm particles deposited on the ground rises from 6.29% to 43.22% of exhaled particles. Therefore, the personalized ventilation can reduce the risk of inhalation in exposed person, and for large size particles, the number of particles falling on the floor increased greatly, which lead to the risk of resuspension increases. The results may be helpful for maximizing the effect of PV in interpersonal airborne disease control.

Numerical simulation of flow pattern for non-Newtonian flow in agitated thin film evaporator

Agitated thin film evaporator (ATFE) is a new type of high-efficiency evaporator where a film is forced to form through a rotating scraper and the high-viscosity non-Newtonian flow materials can be evaporated smoothly. The flow distribution and transmission mechanism of the material in the evaporator directly determine the evaporation efficiency and power consumption of the evaporator. Unlike previous study that was based mainly on Newtonian flow, this paper establishes a three-dimensional computational fluid dynamics model of ATFE for non-Newtonian flow with different viscosities, and systematically probes the flow field distribution characteristics and film forming mechanism in the evaporator. The results show that the flow field distribution characteristics of low-viscosity non-Newtonian flow are similar to those of Newtonian flow, the material can form a uniform and continuous liquid film on the wall; as the viscosity increases, the uniformity and continuity of the liquid film gradually deteriorate. Through studying the flow field distribution and transmission form of the materials, and combining the liquid film distribution, velocity distribution, shear strain rate distribution, and viscosity distribution, it is found that the shear field and viscosity distribution formed by the internal structure and operating state of the evaporator are the key to the good film formation. In addition, it is proposed that the bending of the leading edge of the scraper can assist the spreading of high viscous fluid liquid film, and the best bending angle is explored. This research provides theoretical guidance and basis for the design and application of ATFE.

Numerical modeling of straight and helical elastic rods under fluid flow using immersed boundary method

This paper presents a three-dimensional computational model built using immersed boundary finite volume method to explore the dynamics of straight and helical elastic rods rotating under an applied fluid flow in a channel. Numerical simulations are done for low and high rotational frequencies of a base motor attached at one fixed end of the rods. Simulations reveal that under low rotational frequency, a straight rod (bend at free end) always performs stable twirling motion and eventually attains straight state (mechanical equilibrium) under an applied fluid flow. But on the other hand, for the same conditions a helical rod always keeps its helical shape during interaction with fluid and never attains stable straight state. For the case of high rotational frequency, the straight rod executes whirling motion in which it attains helical shape during all the time. Whirling motion is also observed for helical rod under high rotational frequency. For similar conditions, the instantaneous shapes obtained by straight and helical rods are different which indicates that the initial configuration of the rod as well as rotational frequency have significant impact in deciding the dynamics of the elastic rod under fluid flow. In the biological realm, these elastic rods represent flagellum of monotrichous bacteria which helps for propulsion in fluid. Hence, the present simulation results will help to develop efficient bacteria inspired artificial microrobot for biomedical applications.

О НАДЕЖНОСТИ ОЦЕНКИ ТЕПЛОВОГО РЕЖИМА ПОДЗЕМНОГО ОБЪЕКТА ХРАНЕНИЯ ОТРАБОТАВШЕГО ЯДЕРНОГО ТОПЛИВА НА БАЗЕ ЧИСЛЕННОГО МОДЕЛИРОВАНИЯ

The results of checking the reliability of a previously performed assessment of the thermal mode of an underground facility for long-term storage of spent nuclear fuel in a variant of an integrated reinforced concrete structure on three calculation grids (Coarse, Normal, Fine) are presented. The test was performed on a previously developed three-dimensional computer model in the COMSOL program. The mathematical basis of the model is following: continuity equation, Navier-Stokes equations averaged by Reynolds, standard turbulence model and general heat transfer equation. The consideration of mixed convection conditions was implemented in the "incompressible ideal gas" approximation. It was shown that when using computational grids with high resolution (Normal, Fine), some characteristics may be predicted. They are: temperature increase inside the built-in structure and at the boundary "rock mass - built-in structure" no more than 1°C; a significant change in the structure of the spatial distribution of temperature and an increase in maximum temperatures by about 1°C on the surface of the built-in structure. The duration of calculations in variants with small grids increased approximately 3.4 (Normal) and 7.7 (Fine) times, respectively

Damage characteristics of semi-infinite aluminium targets subjected to normal and oblique projectile impact

The present study investigates the ballistic performance of 50 mm thick 7075-T651 aluminum target against 7.62 API projectile. The focus of this study is to understand the dissipation of total energy engendered by the projectile in impacting the plate target at 0 (normal), 30° and 60° obliquities. Further, the penetration mechanisms and local as well as global plastic deformations developed in the target and projectile were explored. The ballistic experiments on the targets were performed by employing a universal gun and the depth of penetration of the projectile in the target was observed. Three-dimensional computational modelling of projectile and target was carried out in ABAQUS/Explicit module. The material response of both projectile and target was described by the Johnson-Cook strength and damage model. The influence of projectile deformation on the impact resistance of targets was also studied. The plastic strain energy dissipation in the target as well as projectile was evaluated using the validated numerical results and discussed in terms of the damage evolution and local as well as global deformation modes developed in the target and projectile during the impact process.

Математическая и численная модель учета вихревых токов в сплошных элементах магнитопровода линейного электрического генератора с постоянными магнитами

Предложена методика расчета вихревых токов в сплошных элементах магнитных систем линейных электрических генераторов прямоугольного конструктивного исполнения с постоянными магнитами. В основу методики положены расчетные аналитические соотношения для гипотетических контуров вихревых токов, выделяемых в сплошных проводящих элементах магнитных систем. Для проверки адекватности предложенной методики проведен численный расчет на трехмерной компьютерной модели, реализованной в программном комплексе ANSYS Electromagnetic Suite, верифицированном в соответствии с ГОСТ Р 57700.11-2018. Исследованиями подтверждена адекватность методики, погрешность расчетов не превышает 10 %