Large Increments Research Articles

The Influence of the Technical Parameters of the SRS Plans on the Dosimetric and Radiobiologic Evaluation

Background: The purpose of this study was to evaluate influence of technical parameters on Stereotactic Radiosurgery (SRS) plans on dosimetric evaluation. Materials and methods: There were considered and selected two patients who had brain tumors and had been treating in Tomsk Regional Oncology Center. All treatment plans were simulated using the Monaco treatment planning system v 5.11 (Elekta Instrument AB, Stockholm) on the Elekta Synergy linac with photon beam nominal energy 6 MV. For study there were created several plans with different technical parameters (number of arcs, increment, gantry angle, collimator angle, couch angle, minimum segment width). Each plan was evaluated by metrics such as Conformal, Homogeneity and Gradient indexes. Results: If we use a large increment value it may create few sectors and which can produce low quality plans, and increase treatment time, otherwise if we use a too small increment value it will give us more sectors and they can increase the quality of the plan. The dose which was measured with higher MSW showed to us better agreement with the calculated dose. Conclusion: It is valuable to carefully select technical parameters. The use of rigid increment value, segment width or increasing number of arcs can make plans have lower quality and to rise time of treatment.

Enhanced thermoelectric efficiency in Bi-substituted La0.95Sr0.05CoO3

We present the results of a comprehensive investigation of electric and thermal transport properties of polycrystalline Bi-substituted La0.95−xBixSr0.05CoO3 for LBSCO-0, 1, and 2. The electrical resistivity reflects the semiconducting nature with n-type to p-type transition ∼52 K for LBSCO-1 and LBSCO-2 samples. In the low temperature region, the dominant transport mechanism is found to be variable range hopping with the hopping range decreasing with increasing temperature from 95 to 20 Å. The substitution of higher atomic weight element Bi at the La site drastically affects the overall thermal conductivity by reducing the lattice contribution (∼0.12 W/m-K at 50 K) and also enhancing the Seebeck coefficient (S ∼ 354 μV/K). The increase in the resistivity and Seebeck coefficient for the Bi-substituted system is related to the decrease in the available charge carrier concentration (∼5.12 × 1020 cm−3). The overall variation in the Seebeck coefficient depicts a complex nature with a large decreasing trend below 50 K followed by an in-depth analysis of the Debye temperature (∼470 K) and e–ph coupling. These findings suggest that the Bi-substituted LBSCO system has phonon-mediated charge transport via the phonon drag effect below 50 K. Notably, we found a large increment in ZT ∼ 0.17 at room temperature for LBSCO-2 compositions that is one-order larger than pristine undoped LBSCO-0 and even higher than the other existing cobaltite-based thermoelectric choice.

A damage-driven integration scheme in physically non-linear transient analysis for quasi-brittle materials

The standard Newton–Raphson scheme suffers from divergence problems due to softening, negative tangent stiffness, bifurcations or snap-back when modelling fracture of quasi-brittle materials, such as masonry and concrete. Convergence can be achieved by applying sequentially linear analysis (SLA) in some cases. However, it has difficulties in dealing with cases in which the displacement history matters such as dynamic damage modelling due to its total approach. Recently, incremental sequentially linear analysis (ISLA) which combines the merits of the N–R method and SLA, has been proposed. The solution search path follows damage cycles sequentially with secant stiffness corresponding to local damage increments, which traces both damage history (explicit) and displacement history (implicit). This work focuses on dynamic damage modelling of quasi-brittle materials accounting for physical non-linearity as well to address the transient effects in the fracture process. The standard ISLA, similar to the large time increment (LATIN) method, the extended finite element method (X-FEM) and strong discontinuity approaches (SDA) which are proposed to capture the crack propagations for quasi-brittle materials, is not suitable for dynamic damage modelling. The objective of this work is therefore to propose a damage integration scheme (damage-driven instead of time integration scheme) based on ISLA for non-linear transient analysis of structures under dynamic loading while retaining the merits of the previous ISLA. The proposed damage integration scheme has been compared with the standard time integration scheme in a dynamically loaded bar example, showing good agreements and sufficient accuracy. The proposed method has been validated further for a notched beam under tension and four-point bending. Since all physical non-linearity is linearized in damage cycles with the explicit secant stiffness of the reduced elastic material model, the algorithm possesses high robustness.

Fine-grained all-fiber nonlocal dispersion compensation in the telecommunications O-band.

Nonlocal dispersion compensation between broadband nondegenerate photon pairs propagated over fiber corresponding to the ITU-T G.652D telecommunications standard was studied extensively via fine-grained measurements of the temporal correlation between them. We demonstrated near-ideal levels of nonlocal dispersion compensation by adjusting the propagation distance of the photon pairs to preserve photon timing correlations close to the effective instrument resolution of our detection apparatus (41.0±0.1ps). Experimental data indicates that this degree of compensation can be achieved with relatively large fiber increments (1km), compatible with real-world deployment. Ultimately, photon timing correlations were preserved down to 51ps±21ps over two multi-segmented 10km spans of deployed metropolitan fiber.

Numerical investigation on thermal-hydraulic performance of a spiral plate heat exchanger

The thermal-hydraulic performance of counter-current spiral plate heat exchanger (SPHE) under laminar flow regime is numerically investigated by adopting computational fluid dynamics (CFD) and field synergy principle in this paper. The effects of number of turns of spiral and Reynolds number on the average Nusselt number, heat transfer effectiveness, and Euler number are evaluated. The evidence shows that stronger convective heat transfer takes place at inner turns and areas around inner walls of channel. The heat transfer effectiveness increases with reducing increment and Euler number increases with increasing increment as the number of turns increases. When Reynolds number increases, both of heat transfer effectiveness and Euler number decrease due to large increments in mass flow rate. Consequently, an increase in number of turns of spiral at higher Reynolds numbers results in a greater benefit and a lower increment in cost. The numerical results in current research are also compared with the published article. It is found that the effect of thermal resistance of walls plays a vital role in evaluating the relation of heat transfer effectiveness and number of transfer units (NTU) at higher Biot numbers.

A coupled transient gas flow calculation with a simultaneous calorific-value-gradient improved hydrogen tracking

Gas systems can provide considerable flexibility in integrated energy systems to accommodate hydrogen produced from Power-to-Hydrogen units using excess volatile renewable energy generation. To use the flexibility in integrated energy systems while ensuring a secure and reliable system operation, gas system operators need to accurately and easily analyze the effects of varying hydrogen levels on the dynamic gas behavior and vice versa. Existing methods for hydrogen tracking, however, either solve the hydrogen propagation and dynamic gas behavior separately or must cope with a large inaccuracy. Hence, existing methods do not allow an accurate and coupled analysis of gas systems in integrated energy systems considering varying hydrogen levels. This paper proposes a calorific-value-gradient method, which can accurately track the propagation of varying hydrogen levels in a gas system even with large simulation time increments of up to one hour. The new method is joined and simultaneously solved with an implicit finite difference scheme describing the transient gas behavior in a single equation system in a coupled Newton–Raphson gas flow calculation. As larger simulation time increments can be chosen without reducing the accuracy, the computation time can be strongly reduced compared to existing Euler-based methods. With its high accuracy and its coupled approach, this paper provides gas system operators a method to accurately analyze how the propagation of hydrogen affects the entire gas system. With its coupled approach, the presented method can enhance the investigation of integrated energy systems as the transient gas behavior and varying hydrogen propagation of the gas system can be easily included in such analyses.

Hypertrophic adaptations to a 6-week in-season barbell vs. flywheel squat added to regular soccer training.

The aim of this study was to compare the hypertrophic adaptations to barbell or flywheel squat exercise added to regular in-season soccer training. Quadriceps' (rectus femoris [RF], vastus medialis [VM] and vastus lateralis [VL]) cross-sectional area (CSA) in its portions (proximal [PROX], middle [MID], and distal [DIST]) was measured on both legs before and after a 6-week barbell (80 to 90% one-maximum repetition; N.=7) or flywheel (0.0611 to 0.0811 kg·m2; N.=7) in an U19 professional soccer team using a 3T magnetic resonance imaging. Both groups underwent 5 sets × 6 reps per session of squat separated by 3-min rest, while controlling the time under tension (within 0.5 and 0.8 s). The barbell squat group experienced moderate CSA increments in the VM<inf>MID</inf> and the VL<inf>DIST</inf> of the right leg (d=0.98-0.99). Additionally, the flywheel group experience large CSA increments in the RF<inf>MID</inf>, VL<inf>PROX</inf> and VL<inf>MID</inf> of the right leg (d=1.00-1.84). On average, flywheel squat training largely produced greater force during exercise compared to the barbell squat training (29.2 vs. 12.2 N·kg-1; d=5.95), whereas the barbell squat training produced moderately greater power output (10.5 vs. 9.7; d=0.52). Barbell squat training seems to be more effective for VM hypertrophy whereas flywheel squat triggers greater RF and VL hypertrophy as complementary to regular field-based soccer practice and competition within a short range of time (6 weeks) during the in-season. These findings can be considered also from either strength or reconditioning perspective based on the increase in the quadriceps muscles' CSA as mechanism underlying strength/power adaptations.

Comparative Effects of Sodium-Glucose Cotransporter 2 Inhibitors on Serum Electrolyte Levels in Patients with Type 2 Diabetes: A Pairwise and Network Meta-Analysis of Randomized Controlled Trials.

Previous studies have reported that sodium-glucose co-transporter 2 (SGLT2) inhibitors (SGLT2is) affect levels of serum electrolytes, especially magnesium. This study aimed to integrate direct and indirect trial evidence to maximize statistical power to clarify their overall and comparative effects in patients with type 2 diabetes (T2D). We systematically searched PubMed, EMBASE, CENTRAL, and ClinicalTrials.gov up to January 2021 to identify eligible randomized controlled trials (RCTs) of SGLT2is that reported mean changes in serum electrolytes, including magnesium, sodium, potassium, phosphate, and calcium. We performed both random-effects pairwise and network meta-analyses to calculate the weighted mean difference (WMD) and 95% confidence intervals (CI). In total, we included 25 RCTs involving 28,269 patients with T2D and 6 SGLT2is. Compared with placebo, SGLT2is were significantly associated with elevations in serum magnesium by 0.07 mmol/L (95% CI, 0.06 to 0.08 mmol/L) and serum phosphate by 0.03 mmol/L (95% CI, 0.02 to 0.04 mmol/L). Our network meta-analysis showed no evidence of significantly superior efficacy of any specific SGLT2 inhibitor over the others, although dapagliflozin was associated with a larger increment in serum magnesium (WMD=0.16 mmol/L) compared with other SGLT2is. Similarly, no statistically detectable differences among the effects of SGLT2is on serum levels of other electrolytes were detected. SGLT2is significantly increased serum magnesium and phosphate levels, consistent with a class effect of SGLT2 inhibition. However, further investigations of long-term efficacy and safety in patients with T2D with different clinical phenotypes are needed.

Metal–Insulator Transition Driven by Traps in 2D WSe2 Field‐Effect Transistor

AbstractLocalized trap density (Dt) at the 2D channel–gate dielectric interface and its relative strength to carrier–carrier interactions depending on the thickness of the 2D channel can determine the nature of a metal–insulator transition (MIT) in 2D materials. Here, the MIT occurring in WSe2 devices is systematically analyzed by varying the WSe2 thickness from ≈20 nm to monolayer to explore the effects of Dt on MIT. The corresponding critical carrier density increases from ≈8.30 × 1011 to 9.45 × 1012 cm–2 and Dt from ≈6.02 × 1011 to 1.13 × 1013 cm–2 eV–1 as WSe2 thickness decreases from ≈20 nm to monolayer. These large increments in Dt with decreasing thickness of WSe2 induce a strong potential fluctuation in the band of WSe2, causing charge density inhomogeneity in the system, which attributed to tuning the MIT. The critical percolation exponent is strongly dependent on WSe2 thickness with an excellent agreement between the transport data and percolation theory achieved from thinner WSe2 devices, while the transport data measured from multilayer WSe2 devices does not obey the percolation theory. These results suggest that the nature of MIT strongly depends on the WSe2 channel thickness and corresponding unscreened charge impurity and strength of Dt at the interface.

Isotropic etching polishing of belt ground Inconel 718 to improve surface strengthening and quality

Belt grinding (BG), widely used in Inconel 718 machining, can result in desired surface strengthening. However, the grinding-induced strengthening effect diminishes in subsequent belt polishing (BP), thus deserving special attention. This paper proposes isotropic etching polishing (IEP) as an alternative finishing process to effectively retain the robotic BG strengthened layer and concurrently improve the surface quality of BG Inconel 718. The strengthening effect and quality of surface layers processed by BG, BG + BP and BG + IEP are systematically compared and evaluated. The results indicate that BG can introduce an ~150-μm-thickness gradient strengthened layer, featured by high microhardness, significant domain refinement, large microstrain increment, high residual compressive stress, and a strong 〈100〉 texture. The optimized IEP retains approximately 86.1% (maximum) of the strengthening effect and 75.1% of the BG strengthened layer. The microhardness of the BG + IEP surface reaches 523 HV, which is about 6 times higher than that of the BG + BP surface. The BG + IEP surface of superior quality is very smooth (platykurtic) and clean, in contrast to the rough and defective BG + BP surface. The IEP is proposed to be an effective way to simultaneously realize the BG strengthened layer retention and the surface quality improvement.

Manufacturing and characterisation of a new thermal pre-stressed carbon fibre-reinforced lattice core for sandwich panels

Development of high-performance sandwich structures is particularly attractive for aerospace applications, where novel lighter materials and structures are object of extensive research. This work is focused on the design of a new high-performance Carbon FRP core as alternative to traditional periodic prismatic ones. The innovative core is designed as a 2D close-packing pattern of circular cells and manufactured by connecting pre-preg corrugated laminates in specific locations. The corrugated laminates are layered following an asymmetric sequence in order to generate residual thermal stresses within the core to enhance energy absorption and compressive properties. The distribution of the residual thermal stress within the core was numerically studied with a finite element model of the unit cell, in order to prove the positive contribution of the asymmetric layup on the mechanical properties and study the failure mechanisms of the unit-cell. Composite core samples were manufactured, and their mechanical properties were experimentally evaluated through compression, both out-of-plane and in-plane, and beam flexure tests. Results were compared in terms of specific properties with traditional aluminium honeycomb core, showing large increments of specific compressive strength (+84.6%), in-plane compressive modulus (over +500%), Specific Energy Absorption (+145%) and shear (&gt;20%). The FEM model was validated against experimental compressive results, showing an error below 10%. The results show that the core is suitable for applications in novel high-performance sandwich structures, leading to numerous advantages in comparison to traditional cores, such as higher specific properties, manufacturability of complex sandwich structures and higher adhesion and compatibility with CFRP skins.

A variational full-network framework with anisotropic damage and viscoelasticity induced by deformation

Incompressible materials, such as filled rubbers and biological tissues, may exhibit high nonlinear and anisotropic inelastic responses induced by deformations when subject to large strains. The constitutive modeling area has focused on describing the anisotropic behavior of viscosity and damage. However, coupled anisotropic inelastic effects are still a major challenge, with few contributions in the literature. This paper then presents a variational full-network framework capable of representing coupled anisotropic damage and viscoelasticity responses induced by deformation. The proposal extends a variational family to include the advantages of the full-network framework to deal with anisotropic behaviors. Approximations of the potential energies used on the full-network integration scheme associate the inelastic scalar variables at each material point with the quadrature points directions, resulting naturally in a set of scalar minimization problems. Numerical tests are presented to show the ability of the framework to represent anisotropic damage and viscoelasticity. Two variational models, specialized for filled rubber and soft biological tissues, are also implemented on finite element software to assess the model into practical applications. The results show the proposed model’s versatility to simulate anisotropic viscoelasticity, anisotropic mechanical damage, and viscous and damage coupled phenomena, maintaining accuracy for large strain and time increments.

Carbon footprint and water footprint analysis of generating synthetic natural gas from biomass

Bioenergy is generally considered clean and renewable. Water and energy are necessary for producing natural gas from biomass. Analyzing the carbon footprint of the life cycle and water footprint of producing natural gas from biomass can help in the efficient utilization of renewable energy. Carbon dioxide emissions and water consumption in biomass pyrolysis gasification were analyzed. The results showed that the water footprint of natural gas production from biomass is 15.38 L/MJ over its life cycle and that its carbon footprint is 159.24 kg/GJ. Wheat production is the dominant factor in total water consumption, accounting for 98% of the total value. Direct carbon emissions in the natural gas production stage are the main contributor to total emissions, accounting for 69.02% of the latter; water consumption in this process accounts for only 1.06% of the total water use. The effect of eight power generation modes on the total water footprint is small, while their effect on the carbon footprint is large (increments of −3 to −9%). In addition, the effects of 24 scenarios on the final results were investigated through a sensitivity analysis. This study presents relevant carbon emission and water consumption values for a certain range of biomass-to-natural gas production processes. The results obtained herein provide a reference for lowering resource consumption as part of natural gas production and developing environmental investment plans and policies.

Modeling Carbon Budgets and Acidification in the Mediterranean Sea Ecosystem Under Contemporary and Future Climate

We simulate and analyze the effects of a high CO2 emission scenario on the Mediterranean Sea biogeochemical state at the end of the XXI century, with a focus on carbon cycling, budgets and fluxes, within and between the Mediterranean sub-basins, and on ocean acidification. As a result of the overall warming of surface water and exchanges at the boundaries, the model results project an increment in both the plankton primary production and the system total respiration. However, productivity increases less than respiration, so these changes yield to a decreament in the concentrations of total living carbon, chlorophyll, particulate organic carbon and oxygen in the epipelagic layer, and to an increment in the DIC pool all over the basin. In terms of mass budgets, the large increment in the dissolution of atmospheric CO2 results in an increment of most carbon fluxes, including the horizontal exchanges between eastern and western sub-basins, in a reduction of the organic carbon component, and in an increament of the inorganic one. The eastern sub-basin accumulates more than 85% of the absorbed atmospheric CO2. A clear ocean acidification signal is observed all over the basin, quantitatively similar to those projected in most oceans, and well detectable also down to the mesopelagic and bathypelagic layers.

Coal cleat network evolution through liquid nitrogen freeze-thaw cycling

This study investigated the potential of liquid nitrogen (LN2) freeze–thaw process in coal fracturing, focusing on the effect of different freezing cycles. μ-Computed Tomography (μ-CT) images revealed a promising efficiency in cleat network evolution after three freezing cycles. The initial coal showed some fractures with the maximum opening of 15 μm, where the treated coal demonstrated several new fractures with the maximum opening of 10 μm, almost all of which were interconnected to the cleat network. The volume and length of the largest fracture more than doubled, 2.6 × 108 to 5.9 × 108 μm3 and 8 × 105 to 1.9 × 106 μm, due to interconnection with new fractures and isolated fractures. Connectivity analysis illustrated that the number of pores increased by 50% (92715 → 142650), where the number of interconnected pores almost doubled (42060 → 78905). The porosity of the coal also doubled from 0.6% to 1.2% based on μ-CT scan results. SEM along with μ-CT images highlighted more encouraging efficiency of second and third freezing cycles, particularly in terms of enhancing fractures interconnection. SEM images revealed the generation of a thoroughgoing fracture, which increased in aperture size through successive freeze–thaw cycles (17 μm to 48 μm) and extended a cleat network in the coal, particularly in latter cycles. Atomic Force Microscopy demonstrated an increase in the area roughness, which was in a direct relationship with freezing cycles. Mechanical properties analysis revealed more significant damage in the coal in the latter freezing cycles, being initially 3.49 GPa and decreasing to 2.81, 2.11 and 1.52 GPa through three freezing cycles. Finally, the permeability of the coal under 1000 kPa confining pressure increased from 0.035 mD to 0.18 mD, with larger increments in later cycles. Numerical permeability study ran in different directions, where resulted in the most promising enhancement in the Z direction (3.7 to 14 md, 277%).

Use of Discrete fiber in road pavement

Concrete roads are very linear, linear route meansa route that progresses from a starting to an ending point. The beginning and end of a linear route do not meet, but may connect to another route or a destination point and can provide a safe and smooth flow of traffic. Due to the use of concrete in roads it has become quite an advantage for a greater life span and low maintenance. But concrete roads may undergo cracking, spalling and concrete is weak in tension and also little ductility. So as to reduce these problems Inclusion of fiber can provide a great benefit to concrete pavement. This Research “The Use of Discrete Fiber in Road Pavements” is done so as to improve the quality of concrete pavement. In this research the fiber used is polypropylene fiber and polyester fiber. The concrete mix used is M25. (Nominal mix ratio of m25 grade of concrete is1:1:2, mixture of cement, sand, aggregate and water in which one part is cement, one part is sand and two part is aggregate and water cement ratio is 0.4 to 0.6.0). In one specimen only plain, concrete mix is tested for compressive strength, flexural strength and split tensile strength. In second specimen 1.8% of polypropylene fiber is added with the concrete mix and again tested for the same three tests. In the third sample 0.5% of polyester fiber is used in the concrete mix and tested for compressive strength, flexural strength and split tensile strength. In fourth specimen both 1.8% of polypropylene fiber and 0.5 % of polyester fiber is mixed with the concrete mix and tested for the three tests It was seen a large increment in the strength which showed the addition of fiber can improve the quality of concrete.

An unconstrained stress updating algorithm with the line search method for elastoplastic soil models

This paper is devoted to developing an efficient and robust stress updating algorithm in a relatively simple computational framework to address the two difficulties of implementing elastoplastic soil models, namely the nonsmoothness and the nonlinearity. In the proposed algorithm, the nonsmoothness caused by the loading/unloading inequality constraints is eliminated by replacing the Karush-Kuhn-Tucker conditions with the smoothing function. The stress updating can be achieved by solving a set of smooth nonlinear algebraic equations in this algorithm. The nonlinear equations are solved using the line search method, which allows a larger convergence radius of the solution in contrast to the standard Newton method. Meanwhile, the smoothing consistent tangent operator corresponding to the unconstrained stress updating strategy ensures the quadratic convergence speed of the global solution. The modified Cam-clay model is used as an example to demonstrate the implementation of this algorithm. The correctness, computational efficiency, and robustness of the algorithm are validated and assessed by comparing it with the analytical solutions in case of cylindrical cavity expansion and the ABAQUS/Standard default integration method. In simulations with large load increment sizes, the CPU time consumed by the new algorithm can be less than half of the ABAQUS default algorithm.

Pr80Al20 surface-coated DyF3 modified sintered Nd-Fe-B magnets for large coercivity increment via grain boundary diffusion

A large coercivity increment of 11.63 kOe is obtained by grain boundary diffusion with composite powders of Pr80Al20 surface-coated DyF3. The coercivity increases from the original 12.76 kOe to 24.39 kOe and 23.28 kOe in PA-0.7 and PA-0.9 diffused magnets (Pr80Al20:DyF3 = 7:3, 9:1 in wt%), which shows an increase of 91.15% and 82.45%, respectively. The temperature coefficient of coercivity of diffused magnets is improved due to the high magnetic anisotropy field (HA) of (Nd, Pr, Dy)2Fe14B and the optimized microstructure. Excellent diffusion efficiency and Dy diffusion depth are obtained owing to the betterment of Pr-Al-rich grain boundary (GB) phases. Microstructural features show that the combined strengthening effect of magnetic isolation by the continuous Pr-Al-rich GB phases and magnetic hardening by Dy-Pr-rich shells significantly improve the coercivity of the PA-0.7 and PA-0.9 diffused magnets. Especially, no accumulation of Dy element occurs in the PA-0.9 diffused magnet. The composite diffusion sources provide a new method to improve diffusion efficiency of Dy.

Native Forests Show Resilience to Selective Timber Harvesting in Southeast Queensland, Australia

There is little published information on effects of management on the structure of mixed species forests in Queensland, Australia. We used long-term growth, abundance and dimension data from permanent plots to test the hypothesis that harvesting would reduce numbers of large trees and growth increments, while increasing recruitment. This hypothesis is key to policy and management decisions for forests covering about 9.5 million hectares. Inclusion of data on changes in forest structure (e.g., tree diameter, stem density) helps in assessment of forest suitability as habitat for a range of species. Growth rate (basal area) varied widely among forest types. Growth of each of four key species (i.e., Eucalyptus pilularis, Corymbia citriodora ssp. variegata, Callitris glaucophylla, and Eucalyptus crebra) reflected variation in rainfall across the study region. Callitris glaucophylla, a native conifer, is dominant when rainfall is &amp;lt; 600 mm per year. Corymbia citriodora ssp. variegata grows across much wider ranges in rainfall (600–1,200 mm year–1) at rates similar to Callitris glaucophylla. Historic harvesting increased recruitment and also increased the symmetry of diameter distributions. Harvesting has not reduced the current density of larger trees (diameter at breast height, DBH ≥ 60 cm) at a regional scale. Stand growth was unaffected by management principally owing to an increase in the density of trees of smaller diameter (10–20 cm DBH). Self-thinning limits potential stocking and we tested 3 methods for predicting self-thinning across forest types. We found that the slope of self-thinning lines under drier conditions is mostly &amp;lt; –2, suggesting highly dynamic self-thinning. Using a species-boundary line approach, growth is predicted to slow when basal areas reach around 66.1 m2 ha–1 in E. pilularis, 19.0 m2 ha–1 in C. citriodora ssp. variegata, 16.5 m2 ha–1 in Callitris glaucophylla, and 14.2 m2 ha–1 in E. crebra. The slope of the self-thinning line for E. pilularis was –1.662, similar to Reineke’s Stand Density Index (slope –1.605). To date, there is little evidence that selective harvesting and thinning have had negative impacts on rates of growth, on timber production, carbon sequestration or on aspects of forest structure regarded as important for biodiversity.

Development of an Elongated Ellipsoid Heat Source Model to Reduce Computation Time for Directed Energy Deposition Process

Directed Energy Deposition (DED) Additive Manufacturing process for metallic parts are becoming increasingly popular and widely accepted due to their potential of fabricating parts of large dimensions. The complex thermal cycles obtained due to the process physics results in accumulation of residual stress and distortion. However, to accurately model metal deposition heat transfer for large parts, numerical model leads to impractical computation time. In this work, a 3D transient finite element model with Quiet/Active element activation is developed for modeling metal deposition heat transfer analysis of DED process. To accurately model moving heat source, Goldak’s double ellipsoid model is implemented with small enough simulation time increment such that laser moves a distance of its radius over the course of each increment. Considering thin build-wall of Stainless Steel 316L fabricated with different process parameters, numerical results obtained with COMSOL 5.6 Multi-Physics software are successfully validated with experiment temperature data recorded at the substrate during the fabrication of 20 layers. To reduce the computation time, elongated ellipsoid heat input model that averages the heat source over its entire path is implemented. It has been found that by taking such large time increments, numerical model gives inaccurate results. Therefore, the track is divided into several sub-tracks, each of which is applied in one simulation increment. In this work, an investigation is done to find out the correct simulation time increment or sub-track size that leads to reduction in computation time (5–10 times) but still yields sufficiently accurate results (below 10% of relative error on temperature). Also, a Correction factor is introduced that further reduces computation error of elongated heat source. Finally, a new correlation is also established in finding out the correct time increment size and correction factor value to reduce the computation time yielding accurate results.