Compaction Process Research Articles

Identification of modal parameters of soil specimen based on impact force

This study used vibration testing signals of soil samples under external loading to identify modal parameters (including natural frequencies and damping ratios) with different compaction degrees. Based on these parameters, a novel approach was proposed for reliable roadbed vibration compaction control and compaction process optimization. The experimental section utilized six soil samples with varying compaction degrees as experimental subjects, using the hammering method as the excitation mode. Subsequently, the frequency response function and modal parameters of the sample system were obtained through the acquisition, analysis, and parameter identification of samples’ acceleration signals. Firstly, samples with compaction degrees ranging from 88 % to 97 % primarily exhibited three modes, with the second modal frequency response displaying the weakest amplitude, and the fundamental mode being the dominant one. Additionally, parameter identification results revealed that the fundamental modal frequency exhibited a significant negative exponential growth with increasing compaction degree, while the second and third modal frequencies showed significant linear growth. Furthermore, the average damping ratio also demonstrated a tendency toward linear change with increasing compaction degree. Finally, the feasibility of modal parameters being actively used in practical engineering is discussed. Consequently, this study aimed to propose an indicator system for accurately assessing the bearing level of compacted soils from a modal dynamics perspective and to integrate modal dynamic indicators with density-class indicators into further optimization design work on road compaction processes.

Superior uniform deformation ability of intragranular nano TiB reinforced Ti-6.5Al–2Zr–Mo–V fabricated by hot isostatic pressing

In order to improve the uniform deformation ability of titanium matrix composites, the intragranular nano-TiB whiskers (TiBnw) reinforced Ti-6.5Al–2Zr–1Mo–1V (TA15) composite was designed and fabricated by hot isostatic pressing (HIP) at the temperature of 1000 °C. The TiBnw was successfully planted into the pre-alloyed powders before HIP. The composite sintered for 6h (HIP-6h) realized a complete densification process benefiting from a high sintering pressure of 150 MPa. While the 2h sintering process (HIP-2h) was insufficient to densify. The HIP-6h exhibited an unparalleled uniform elongation of 9.5 %, which was superior to the survey TA15 matrix titanium composites. The excellent uniform deformation ability was demonstrated to be associated with the equiaxed structure and the blocking and multiplication effect on dislocations from the intragranular TiBnw.

Rapid preparation of Si3N4 ceramics with high thermal conductivity and low dielectric loss by fast hot-pressing (FHP) sintering

A series of Si3N4 ceramics with MgO and Y2O3 as sintering additives were successfully prepared by fast hot-pressing (FHP) sintering at the sintering temperature of 1700 °C, with the hold time of only 10 min and the whole sintering process of 36 min. The sintering behavior, densification process, microstructure, crystalline phase composition, bond composition, thermal conductivity and dielectric properties were systematically investigated. FHP reduces the sintering temperature and sintering time of Si3N4 ceramic compared to traditional solid-state method. The results of a series of tests have shown that the densification of Si3N4 ceramics and the phase transition from α-Si3N4 to β-Si3N4 can be facilitated by appropriate levels of additives, resulting in a dense, homogeneous and non-porous microstructure. Additionally, based on test results in this work, Si3N4 -4 wt.% Y2O3 -2 wt.% MgO exhibit the highest thermal conductivity of 78.16 W/mK, the dielectric constant of 8.50 and the dielectric loss of 5.52 × 10−4. The Si3N4 ceramics investigated in this work exhibit excellent properties for use of power semiconductor device packages, microwave devices, and power electronics. And also demonstrate the potential of FHP in laying the foundation for the further preparation of higher performance Si3N4 ceramics.

Improved reservoir quality assessment by evaluating illite grain coatings, quartz cementation, and compaction – Case study from the Buntsandstein, Upper Rhine Graben, Germany

Reservoir quality (RQ) in the Buntsandstein of the Upper Rhine Graben is in the center of attention as it is a possible target formation for geothermal energy production and hydrocarbon exploration surrounding existing fields. An understanding of properties affecting reservoir quality of the target lithology is still fairly poor and the success of accurately targeting high RQ intervals is limited. This is due to the fact, that the effect of compaction and the interplay between enhanced chemical compaction (i.e. pressure dissolution of quartz grains), illitic contact coatings and quartz cementation in the lithology has been underestimated. The understanding and quantification of controlling factors on reservoir qualities in fluvio-eolian sedimentary rocks, deposited in a (semi-)arid climate has been improved in recent years and this case study highlights the benefits of detailed petrographic analyses in understanding diagenetic and compactional processes in this lithology. This is especially relevant in the observation of grain coating clay minerals, whose effect depends on their specific location, i.e. either at grain contacts between quartz grains (GTG coating) or at the interface between detrital quartz grains and the intergranular volume (GTI coating).Illitic GTI coatings affect syntaxial quartz overgrowth precipitation, as precipitation sites are locally blocked. The negative correlation between the grain coating coverage and quartz cement volumes support these findings across multiple sample sets, and they may locally preserve intergranular porosity. Illitic GTG coatings on the other hand enhance chemical compaction (i.e. pressure dissolution) and will reduce the IGV. The negative correlation between these two properties again underlines the negative effect of this process on reservoir properties. Studied samples from a deep Buntsandstein well in the central URG show low reservoir quality due to either intense quartz cementation (0.7–31.7%) or a high degree of mechanical and chemical compaction (IGV: 2.3–38.0%). Higher illitic GTG and GTI coating coverages play a substantial role in controlling reservoir quality development, as demonstrated by comparing data from other fluvio-eolian lithologies (Triassic Buntsandstein and Permian Rotliegendes) to results of this study. In relation to their respective burial histories, higher illitic GTI coating coverages always correlate with smaller syntaxial quartz cement volumes. Similarly, higher illitic GTG coating coverages always correlate with lower IGV values in the three compared sample series.As both, the precipitation of quartz cements and compaction, are a function of the burial history, i.e. effective stresses and experienced temperatures, understanding the interaction of both these processes may enable the prediction of reservoir properties in undrilled areas.

Structural properties of LATP ceramic pellets sintered at 900 °C and modified by a novel solution-immersion densification process

The high temperature sintered ceramic pellets of solid electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP), obtained in the absence of any sintering aids, should contain a large amount of interparticle gaps, which is one of the main bottlenecks in developing LATP-based all-solid-state Li-metal batteries. In this study, a facile solution (LiCl in ethanol) immersion method is adopted to soak the already 900℃-sintered LATP ceramic pellets, and the resulting series of LATP-xLiCl (x denotes the weight fraction of LiCl, 0.0 ≤ x ≤ 3.7) are assayed to address the high-performance mechanism of lithium-graphite (Li-C) symmetric cells. At the optimal x value of 2.3, the grain-boundary resistance of the ceramic pellet can be significantly reduced from 1772 to 28 Ω·cm² at room temperature, which endows the Li-C symmetrical cells of LATP-2.3LiCl with a high critical current density of 3.00 mA cm² at 60°C. Especially, the enhanced ionic conductivity of LATP-2.3LiCl (4.7×10−4 S cm−1, at 20℃; 1.1×10−3 S cm−1, at 60℃) indicates an effective strategy of utilizing capillary force to densify LATP-based ceramic pellets for potential application purposes.

Advanced ion-selective wood membranes: Leveraging aligned cellulose nanofibers for enhanced osmotic energy conversion

Nanofluidic reverse electrodialysis (RED) is widely recognized as an exceptionally effective method for harvesting osmotic energy. Nevertheless, its progress has been impeded by the high costs and intricate fabrication processes associated with the required ion exchange membranes. The ion-selective wood membranes (ISWM) are derived directly from natural wood through a meticulously designed two-step chemical modification and densification process. The obtained ISWM with a highly charged surface effectively preserves the alignment of nanochannels from the cellulose fibers sourced in natural wood. Moreover, the laminated structure consisting of oriented nanofibers enhances ion conductivity by a factor of 4 compared to natural wood birch under low KCl concentrations. The charged and aligned nanochannels serve as nanofluidic conduits, facilitating selective ion transport. This, in turn, engenders efficient charge separation and the generation of an electrochemical potential difference. In energy harvesting systems such as ISWM-RED, the synergistic interplay between the electrochemical potential difference and ionic flux manifests in a remarkable output power density, reaching up to 658 mW m−2 to a salinity gradient of KCl at a magnitude of 50-fold. ISWM is an outstanding nanofluidic material that provides a cost-effective and easy-to-prepare solution for producing natural nanofluidic materials. Our investigation delineates a promising trajectory for developing high-performance nanofluidic RED devices tailored for efficient osmotic energy harvesting from renewable and abundant natural resources.

Influence of particle breakage on bulk density of dynamically compacted coarse aggregates

The article presents the first discrete element method (DEM) simulations of dynamic compaction in the Proctor test. The aim of the simulations was to analyze the influence of particle breakage on the density of intensely compacted granular assembly. Results from simulations and laboratory tests were compared. Simulations with non-breakable aggregates enabled separation of the influence of change in particle size distribution and particle rearrangement. Both factors play an essential role in increasing the bulk density of the sample in the case of the tested (gap-graded) aggregate. Simulations with breakable particles reproduce the laboratory tests results better, both qualitatively and quantitatively. The conclusions provide a better understanding of the aggregate compaction process, which is crucial for developing novel compaction strategies and minimizing the environmental impact of the construction process.

Crystallization and microwave dielectric properties of CaO-B2O3-SiO2 glass-ceramic/Al2O3 for LTCC applications

High-frequency electronic devices with low dielectric loss and electronic components with high integration densities require high-performance electronic packaging materials. In this study, materials primarily composed of CaO-B2O3-SiO2 (CBS) with an elevated boron content were fabricated through solid-phase sintering using Al2O3 as the ceramic phase. The phase compositions, densification process, microstructures, thermal conductivity, thermal expansion, and dielectric properties of the LTCC were investigated. Remarkably, the CBS-1 LTCC composite sintered at 850 °C for 4 h, exhibited a dense and nonporous microstructure. It demonstrated exceptional thermoelectric properties, including a thermal shrinkage of 5.61 %, coefficients of thermal expansion of 4.86 ppm/°C, thermal conductivity of 2.36 W/m·K, dielectric constant (εr) of 4.88, and tan δ of 1.05× 10−3 at 15 GHz. These characteristics are conducive to minimizing the signal propagation time delay and filtering noisy signals. Consequently, the CBS-1 LTCC composite emerged as a promising substrate for LTCC applications.

A Fusion Positioning System Based on Camera and LiDAR for Unmanned Rollers in Tunnel Construction.

As an important vehicle in road construction, the unmanned roller is rapidly advancing in its autonomous compaction capabilities. To overcome the challenges of GNSS positioning failure during tunnel construction and diminished visual positioning accuracy under different illumination levels, we propose a feature-layer fusion positioning system based on a camera and LiDAR. This system integrates loop closure detection and LiDAR odometry into the visual odometry framework. Furthermore, recognizing the prevalence of similar scenes in tunnels, we innovatively combine loop closure detection with the compaction process of rollers in fixed areas, proposing a selection method for loop closure candidate frames based on the compaction process. Through on-site experiments, it is shown that this method not only enhances the accuracy of loop closure detection in similar environments but also reduces the runtime. Compared with visual systems, in static positioning tests, the longitudinal and lateral accuracy of the fusion system are improved by 12 mm and 11 mm, respectively. In straight-line compaction tests under different illumination levels, the average lateral error increases by 34.1% and 32.8%, respectively. In lane-changing compaction tests, this system enhances the positioning accuracy by 33% in dim environments, demonstrating the superior positioning accuracy of the fusion positioning system amid illumination changes in tunnels.

Predicting hardness of graphene-added Si3N4 using machine learning: A data-driven approach

This study presents a data-driven framework based on machine learning (ML) using extreme gradient boosting (XGBoost) for predicting the hardness of silicon nitride (Si3N4) ceramics reinforced with graphene. The XGBoost model takes into account various factors such as graphene type and content, characteristics of the raw Si3N4 powder, the parameters of the sintering process (sintering technique, temperature, pressure, holding time), and the characteristics of the sintered samples, i.e., the density, αβ content and Vickers hardness. The parameters that influence the Si3N4 hardness most strongly are identified, with sintering pressure, sintering time and density being the most influential. The addition of graphene content up to a certain threshold (1 wt%) has a positive impact on hardness. However, beyond that it leads to a lower density and a lower mechanical performance. Sintering parameters, particularly the sintering pressure, temperature, holding time and technique, strongly affect the density, final grain size, αβ Si3N4 composition and subsequently the hardness. The study highlights the importance of density and the densification process in achieving high hardness in Si3N4 ceramics. The developed ML model provides a valuable tool for predicting the hardness of Si3N4+graphene ceramics composites and offers insights into selecting suitable graphene type, content, and processing parameters. While the study primarily focuses on Si3N4+graphene composites, this novel approach holds promise for the in-silico design and analysis of diverse ceramic materials.

O-063 How does the exclusion of blastomeres affect the outcome of euploid blastocysts?

Abstract Study question Do euploid blastocysts with excluded blastomere(s) have the same probability of live birth when compared to euploid blastocysts without excluded blastomere(s)? Summary answer Euploid blastocysts with excluded blastomere(s) have significantly worse pregnancy outcomes, with the live birth rate being 10% lower than those without any exclusion pattern. What is known already Blastomeres that have arisen at any time throughout cleavage-stage are sometimes excluded from the formation of the blastocyst and once isolated, those cells do not take further part in preimplantation development. Embryos harboring cell exclusion were found to have altered morphokinetic profiles; S2(second synchrony) and ECC3(embryonic cell cycle 3) were described as useful in identifying increased odds of FHB when a cell exclusion event was present (Kakulavarapua et al., 2023). Besides, pregnancy and live birth rates were reported to progressively decrease in a non-PGT-A (preimplantation genetic testing for aneuploidy) tested cohort with excluded or extruded blastomere(s) (Coticchio et al., 2021). Study design, size, duration This retrospective study included 667 euploid blastocysts with excluded blastomere(s) and 3830 euploid blastocysts without excluded blastomere(s). All were transferred between 2017 and 2023. No discrimination was made between cells failing to compact because of their exclusion from the compaction process (excluded from a partially compacted morula), and cells extruded after an initial inclusion in the compacted embryonic mass (extruded from a partially compacted morula). Participants/materials, setting, methods A total of 4497 IVF patients treated in a single private clinic were included in this retrospective study. Their blastocysts were subjected to PGT-A mainly for advanced maternal age. The analysis was done by next generation sequencing (NGS) (Ion Torrent S5, Thermo Fisher). Vitrified-warmed euploid blastocysts were then transferred in a next cycle. Pregnancy and miscarriage rates were compared between blastocysts with and without excluded blastomere(s) by chi-square test. Main results and the role of chance The outcomes of euploid blastocysts with excluded blastomeres (n = 667) were compared to euploid blastocysts without excluded blastomeres (n = 3830). The biochemical pregnancy rate was 71.6% and 77%, respectively (p = 0.0026). The clinical pregnancy rate was 61.3% and 70.6%, respectively (p = 0.0001). The ongoing pregnancy rate was 53.7% and 63.3%, respectively (p = 0.0001). The biochemical miscarriage rate nearly doubled with the presence of excluded blastomere(s) (14% vs. 8.3%, respectively; p = 0.0001). The clinical miscarriage rate was 12.7% and 10.4%, respectively (ns). Ultimately, the live birth rate was 46.3% for the blastocysts with excluded blastomere(s), compared to 57.6% for the blastocysts without excluded blastomere(s) (p = 0.0001). Limitations, reasons for caution No discrimination was made between cells excluded from a partially compacted morula and cells extruded after an initial inclusion in the compacted embryonic mass. Wider implications of the findings Although blastocysts with excluded blastomere(s) are not the first choice for transfer, our results show that, although at lower rate, successful pregnancies and live births occur. A complete time-lapse culture evaluation not limited to cell division time points may propose indicators to identify higher implantation potential blastocysts with excluded blastomere(s). Trial registration number N/A

Sintering Mechanism of Pure B4C Ceramic Prepared by Hot Oscillating Pressing and with Excellent Mechanical Properties

Pure boron carbide (B4C) ceramics are sintered by hot oscillating pressing at temperatures of 1700–1900 °C for different soaking times. The densification mechanism, grain growth kinetics, and mechanical properties obtained under these sintering conditions are systematically investigated. It is found that the fully densified B4C ceramic is obtained at 1900 °C within 120 min, possessing an excellent combination of hardness (≈38.5 GPa) and fracture toughness (4.8 MPa m1/2). The densification mechanisms during sintering are as follows: viscous flow at the initial stage (relative density D ranged from 55% to 65%) under 1700 °C; lattice diffusion/grain boundary diffusion at the sintering stage (62% < < 75%) of 1800 and 1850 °C; grain boundary sliding by dislocation motion at the late stage (65% < < 82%) of 1700 °C and the sintering stage (75% < D < 90%) at 1800–1900 °C; and dislocation gliding and stacking faults at the final stage (90% < D < 95%) occurring at 1850–1900 °C. The dislocation motion exhibits a critical impact on the densification process of the hot oscillating–pressed B4C ceramic. The grain growth kinetics at 1900 °C is controlled by grain boundary diffusion.

The multidimensional nature of the Environmental Contribution for environmental qualification in São Paulo

This paper describes the conception of the Environmental Contribution instrument in the municipality of São Paulo, with the aim of exploring the multidimensional nature of this instrument, namely: its potential to promote improvements in the city's drainage system, microclimate conditions and biodiversity, as well as encouraging the development of sustainable buildings through certification and promoting environmental quality in the densification process. It also takes stock of the implementation of the instrument in the city of São Paulo between 2016 and 2023, through the project approval reports from the Municipal Urban Planning and Licensing Department (UPLD). In this context, the multidimensional nature of the instrument and its high potential to promote improvements in the city's environmental quality and to contribute to São Paulo's adaptation to the impact of climate change are proven. At the same time, the instrument's scope is limited, and it urgently needs to be improved so that the Environmental Contribution has a wider reach in the territory and is consequently more effective in improving the city's environmental quality.

Study on compaction characteristics and mechanical model of dry crushing filling material under lateral confinement condition

The compaction characteristics and bearing capacity of dry filling materials in goaf have a significant influence on stope control and surface stability. Through acoustic emission monitoring and mechanical model analysis, a series of confined compression tests were conducted on crushed waste with varying particle sizes and Talbot coefficients. The deformation, fragmentation, and acoustic emission characteristics under corresponding working conditions were determined. The results indicate that the stress–strain curves of crushed stone with different particle sizes and Talbot coefficients exhibit similar nonlinear behavior during confined compression. However, the strain response varies with changing stress levels. By analyzing the slope change rate of the stress–strain curve, the lateral uniaxial compression process of waste rock can be divided into three deformation stages: rapid compression, stable crushing, and slow compaction. The compressive deformation characteristics of gravel differ based on particle size and Talbot coefficient. Specimens with a higher Talbot coefficient demonstrate stronger compressive resistance and weaker deformation resistance during initial compaction loading. Notably, the internal pressure structure strength is influenced by factors such as maximum particle size D, grading coefficient n, and particle size distribution continuity, rather than solely by the proportion of large particles. The evolution of acoustic emission signals and energy-time curve during waste rock confined axial compression synchronizes with the compaction process. Overall, compaction plays a critical role in maintaining the stability of goaf in dry crushed waste filling.

Influence of the Chemical Modification of Carbon Nanotube Fibers on Electrical properties and Electromechanical Response

The electromechanical response (EMR) of carbon nanotube (CNT) fibers is related to the densification process of the CNT network driven by electromagnetic force. The study of the interaction between the electrical properties and the electromechanical response of carbon nanotubes is of great theoretical significance for exploring the microstructure of carbon nanotube fibers and developing the related flexible electronic devices. This study investigated the relationship between the conductive pathway network and EMR, by analyzing the internal structural characteristics of the CNT fibers after undergoing hydrogen peroxide oxidation and iodine modification. The results show that impurities such as amorphous carbon impeded electron transport and deformation of CNT networks. After hydrogen peroxide oxidation treatment, he carbon nanotube surface impurities inside the fibres were reduced, the van der Waals forces between carbon nanotubes were increased, the deformation of the carbon nanotube network was enhanced, and the negative effect of the decrease in the elastic modulus of the fibres caused by the increase in temperature was weakened. In the case of iodine-decorated CNT fibers, carbon-iodine bonds effectively strengthened the interaction between CNTs, but hinders the contraction of the carbon nanotube network, resulting in a weaker electromechanical response. Hydrogen peroxide oxidation treatment is more beneficial than iodine modification to improve the shrinkage and deformation ability of carbon nanotube fibres in the electromechanical response.

Thermodynamic Coupling Forming Performance of Short Fiber-Reinforced PEEK by Additive Manufacturing.

In this work, the PEEK/short carbon fiber (CF) composites were prepared, a new thermodynamic coupling (preheating and impact compaction) process of the FDM method is proposed, and the warp deformation mechanism was obtained by finite element simulation analysis. Results show that a new method could improve the forming quality of an FDM sample. The porosity of FDM samples of the PEEK/CF composite gradually decreased from 10.15% to 6.83% with the increase in impact temperature and frequency. However, the interlayer bonding performance was reduced from 16.9 MPa to 8.50 MPa, which was attributed to the influence of the printing layer height change from the printhead to the forming layer. To explain the above phenomenon, a thermodynamic coupling model was established and a relevant mechanism was analyzed to better understand the interlayer mechanical and porosity properties of PEEK/CF composites. The study reported here provides a reference for improving the forming quality of fabricated PEEK/CF composites by FDM.

Finite Element Analysis of Densification Process in High Velocity Compaction of Iron-Based Powder.

A finite element model based on elastic-plastic theory was conducted to study the densification process of iron-based powder metallurgy during high velocity compaction (HVC). The densification process of HVC at different heights was simulated using MSC Marc 2020 software with the Shima-Oyane model, and compared with the experimental results. The numerical simulation results were consistent with the experimental results, proving the reliability of the finite element model. Through finite element analysis and theoretical calculation, the high-speed impact molding process of metal powder was analyzed, and the optimal empirical compaction equation for iron-based powder high-speed impact molding was obtained. At the same time, the influence of impact velocity and impact energy on the relative density distribution cloud map and numerical values of the compact was analyzed.

SPATIAL CORRELATION BETWEEN SUFFOSION PROCESSES AND LAND USE IN SĂLCUȚA PLAIN (SOUTHWESTERN ROMANIA)

The present study aims to establish how the agricultural lands in Sălcuța Plain, a piedmont subunit of the Romanian Plain, are affected by the presence of micro-depressions on loess deposits. The formation of these micro-depressions is closely related to the chemical and mechanical compaction process, which is conditioned by several factors, including the thickness of the loess deposit, the quantity of carbonates in the deposit, local morphometry, paleogeographic evolution, and climatic conditions. Based on satellite imagery from the 2010-2019 period, 303 micro-depressions were identified. Out of the total number of depressions, 293 are located on agricultural lands, covering approximately 9.31 km2. On the surface of some of these depressions, soils with stagnant horizons (0.7 km2) have formed due to prolonged excess moisture. These types of soils gradually lead to the long-term degradation of agricultural lands. It is recommended to constantly monitor the evolution of soils with stagnant horizons and implement ameliorative agricultural measures in case an expansion of their area is observed in the long term.

IMPLEMENTASI METODE WEIGHTED AGGREGATED SUM PRODUCT ASSESMENT DALAM MENENTUKAN KEDELAI TERBAIK PRODUKSI TAHU, TEMPE

This research aims to implement the Weighted Aggregated Sum Product Assessment method in identifying soybeans as raw materials in the production of tofu and tempeh. Tofu and tempeh production often experiences production failures, such as the tofu compaction process being insufficient or the texture being too dense, the tempeh fermentation process being less than optimal and so on. This is influenced by poor soybean raw materials, both in terms of texture and color and the selection of soybeans which is still done directly by looking at the color and brand. Meanwhile, these two things do not necessarily correspond to the right criteria for tofu and tempeh production. In this research, the Weighted Aggregated Sum Product Assessment method was used in making decisions to determine the best soybeans for producing tofu and tempeh based on 4 selection criteria, namely soy color, soy size, soy moisture and soy texture. All these criteria are then processed to obtain the best soybean results that are appropriate for the raw material for making tofu and tempe, namely soybeans from the Ahok supplier with a value of 4.475.

Using in situ UO2 bicrystal sintering to understand grain boundary dislocation nucleation kinetics and creep

AbstractCapillary evolution at bicrystal UO2 grain boundaries is characterized using in situ transmission electron microscopy. The discontinuous nature of the densification process, both particle rotation and axial strain, along with the large activation stress for densification support a hypothesis that grain boundary strain in UO2 follows nucleation rate limited kinetics at low to intermediate stresses, that is, less than . The temperature dependence of the average activation stress for sintering agrees well with analysis of bulk sintering data and creep data reported within the literature when analyzed in the context of a grain boundary dislocation nucleation rate limited kinetic model.