Growth Rate Equation Research Articles

Biological aspect and dynamic population of fringescale sardine (Sardinella fimbriata: Valenciennes, 1847) in Prigi waters Trenggalek, East Java, Indonesia

Fringescale sardine (Sardinella fimbriata) is one of important species caught in Prigi waters, Trenggalek, East Java. The existence of fringescale sardine as marine fisheries commodity plays an important role in Prigi fisheries community. This research was conducted in Prigi waters from December 2018 to July 2019 aimed to determine the biological aspects, to illustrate some dynamic population parameters, and to identify food composition. This study applied a descriptive method and random sampling for data collection. There were 1,375 fish have been assessed with total length (TL) ranging from 10 cm to 20.4 cm. Results indicated that growth patterns of the fish was negative allometric with length weight relationship equation was W = 0.014L2.804. Sex ratio of male and female obtained was 1: 1. The gonad maturity level analysis found that proportion of mature and immature fish was equal. The gonadosomatic index value was ranged from 0.57% to 2.42%. The values of length at first capture and length at first mature were 15.35 cm and 16.07 cm, respectively. The growth rate equation obtained in this study was Lt = 26.75 (1-e0.92 (t+0.178)). Mortality rates, total and fishing were 1.709 and 0.286, respectively, while the exploitation rate was 0.167. Additional assessment showed that the main food of the fringescale sardine was phylum Arthropods with index of preponderance (IP) value was 61.5%. It can be concluded that the fish was a plankton feeder and status of the stock was in over fishing condition.

Clinical Outcome of Residual Liver Volume and Hepatic Steatosis After Right-Lobe Living-Donor Hepatectomy.

BackgroundWe examine how residual liver volume (RLV) and hepatic steatosis (HS) of living liver donors affect the regeneration process and clinical outcomes.Material/MethodsWe longitudinally studied 58 donors who underwent right-lobe hepatectomy during the period February 2014 to February 2015 at a single medical institution. The patients were classified based on RLV (30–35%, 35–40%, 40–50%) subgroups and HS (<10%, 10–30%, 30–50%) subgroups. Clinical parameters such as clinical outcome, liver volumetric recovery (LVR,%) rate and remnant left-liver (RLL,%) growth rate were collected for analysis.ResultsThe clinical features of postoperative peak total bilirubin (p=.024) were significant in the 3 RLV subgroups. Body mass index (p=.017), preoperative alanine transaminase (p<.001), and pleural effusion (p=.038) were significant in the 3 HS subgroups. The LVR rate and RLL growth rate equations showed significant variation in regeneration among the 3 RLV subgroups. The LVR rate and RLL growth rate equations did not show significant variation in regeneration among the 3 HS subgroups.ConclusionsHyperbilirubinemia was a risk factor in the small-RLV group, and a large amount of pleural effusion was a risk factor in the steatosis 30–50% group. Hepatic steatosis subgroups did not show significantly different degrees of regeneration. The safety of living donors was a major concern while we compiled the extended living-donor criteria presented in this paper.

Demographic Transition in the Past and Projected Five Decades in Sub-Saharan Africa, 1967-2068: Empirical Evidence from Nigeria

Aims: This study assessed the demographic transition in the past and projected five decades in Sub-Saharan Africa, 1967-2068: Empirical evidence from Nigeria.&#x0D; Study Design: Past and projected time series data (between 1967 and 2068) were used for the study. The 1967-2068 data sets were resorted to due to lack of complete national data.&#x0D; Place and Duration of Study: Past (between 1967 and 2017) and projected (between 2018 and 2068) five decades in Nigeria.&#x0D; Methodology: The time series data (1967 to 2068) obtained from the 1950-2099 Interpolated Demographic Data of the United Nations Population Division, Department of Economic and Social Affairs, on Births, Deaths and Population levels, were used for the study. The 1967-2068 data sets were resorted to due to lack of complete national data. Data collected were analyzed using birth and death rate indices, demographic transition index, growth rate equation and granger causality statistics. Unit root, co-integration and error correction tests were also carried out.&#x0D; Results: Results showed that in the past five decades (1967-2017), the mean crude birth and death rates per 1,000 populations were 43.9 and 18.0 respectively; while that of the projected five decades (2018-2068) was 28.9 and 7.9 respectively per 1000 populations. The demographic indices showed that in the past five decades (between 1967 and 2017), Nigeria was at the second stage (stage II) of demographic transition and expected to remain at this stage in the next five decades (between 2018 and 2068). Results also showed that the population growth rate in the past five decades was 2.584 percent, while the growth rate in the next five decades as projected was 2.098 percent. The population growth rate (2.098 percent) in the next five decades (between 2018 and 2068 as projected) is expected to decrease by an average of 0.486 percent. Results also showed that there is a mutual link between demographic transition and population growth.&#x0D; Conclusion: Nigeria is currently at the second stage of demographic transition and expected to remain at this stage (stage II) in the next five decades. Demographic transition increases the prediction of population growth and vice versa.

Лимитирующие режимы роста III-V нитевидных нанокристаллов

Theoretical analysis is presented for vapor-liquid-solid growth of III-V nanowires in the presence of three competing processes of the group V deposition, surface diffusion of group III adatoms and nucleation of islands at the liquid-solid interface. A generalized equation for the nanowire growth rate is obtained which can be limited of one of the three processes depending on the growth environment. Different regimes of vapor-liquid-solid growth of III-V nanowires are analyzed depending on the group III and V influxes and nanowire radius.

Growth Rate and Histamine Production of Citrobacter freundii CK01 in Various Incubation Temperatures

Improper handling and temperature fluctuations during postharvest of fish commonly allow the growth of histamine-forming bacteria (HFB) that may cause histamine poisoning. Citrobacter freundii CK01 is one of the HFB isolated from Skipjack landed on Sadeng, Yogyakarta. This study aimed to determine the temperature effect on the growth rate and histamine production by C. freundii CK01. Bacterial growth and histamine production was tested in tuna fish infusion broth (TFIB) at 5, 15, 30 and 40°C. The bacterial growth was tested using Total Plate Count method, while histamine was determined using Thin Layer Chromatography and densitometry method. The primary model for bacterial growth was plotted with incubation time using DMFit referred to Baranyi &amp; Roberts model. The secondary model was converted from growth rate and modeled using Ratkowsky Square Root Model. The equation for growth rate of C. freundii CK01 was μmax=[0.0105 (T + 13.886)]2 (Root Mean Square Error &lt;10%). Histamine production reached the highest concentration at 15°C in 96 hours up to 117,13 ppm. This study shows that temperature affected the growth rate and histamine production of C. freundii, indicating the importance of maintaining the low temperature stability during handling of skipjack.

Food-web fluxes support high rates of mesozooplankton respiration and production in the equatorial Pacific

We investigated how the network of food-web flows in open-ocean systems might support high rates of mesozooplankton respiration and production by comparing predicted rates from empirical relationships to independently determined solutions from an inverse model based on tightly constrained field-measured rates for the equatorial Pacific. Model results were consistent with estimates of gross:net primary production (GPP:NPP), bacterial production:NPP, sinking particulate export, and total export for the equatorial Pacific, as well as general literature values for growth efficiencies of bacteria, protozooplankton, and metazooplankton. Mean rate estimates from the model compared favorably with the respiration predictions from Ikeda (1985; Mar Biol 85:1-11) (146 vs. 144 mg C m-2 d-1, respectively) and with production estimates from the growth rate equation of Hirst &amp; Sheader (1997; Mar Ecol Prog Ser 154:155-165) (153 vs. 144 mg C m-2 d-1). Metazooplankton nutritional requirements are met with a mixed diet of protozooplankton (39%), phytoplankton (36%), detritus (15%), and carnivory (10%). Within the food-web network, NPP of 896 mg C m-2 d-1 supports a total heterotrophic carbon demand from bacteria, protozoa, and metazooplankton that is 2.5 times higher. Scaling our results to primary production and zooplankton biomass at Stn ALOHA suggests that zooplankton nutritional requirements for high growth might similarly be met in oligotrophic subtropical waters through a less efficient trophic structure. Metazooplankton production available to higher-level consumers is a significant contributor to the total export needed for an overall biogeochemical balance of the region and to export requirements to meet carbon demand in the mesopelagic depth range.

Crack growth rate and lifetime prediction for aviation gas turbine engine compressor disk based on nonlinear fracture mechanics parameters

In this study, the fatigue crack growth and life-time prediction of aviation gas turbine engine compressor disks under operating conditions are analyzed. Different combinations of rotational speed, temperature, surface flaw forms and sizes, as well as elastic–plastic titanium alloy BT3-1 properties are considered. A crack growth rate equation, which included the fracture process zone size and nonlinear stress intensity factor, is derived. The assessments of the structural integrity of the rotating disk are compared for elastic and elastic-plastic solutions. It is indicated that the traditional elastic crack growth models overestimate the residual fatigue lifetime with respect to the nonlinear fracture mechanics approach.

Creep–fatigue crack growth rate prediction based on fracture damage zone models

Based on a new fracture damage zone formulation and nonlinear elastic–plastic and creep crack tip fields, the prediction of creep–fatigue crack growth rate is studied. A unified crack growth rate equation is derived using the equivalent nonlinear stress intensity factor, monotonic low-cycle fatigue, and creep material properties at an elevated temperature. The crack growth rate model includes the size of the fracture process zone and damage parameters. The predicted creep–fatigue crack growth rates are compared with the experimental data of the 12Cr1MoV power plant steel and good agreement is observed.

Mesoscopic Model for the Condensation of a Metallic Vapor

A computing scheme for a mesoscopic description of a nucleation process has been built using a statistical analysis of the results of molecular dynamics simulation of a supersaturated metallic vapor. The parameters that enter into equations for cluster growth rate and heat release during condensation are found by a direct statistical computation in a molecular dynamics method. The rates of cluster formation calculated by a molecular dynamics method agree well with the numerical model developed in this work.

Surfactant- and gravity-dependent instability of two-layer channel flows: linear theory covering all wavelengths. Part 2. Mid-wave regimes

The joint effects of an insoluble surfactant and gravity on the linear stability of a two-layer Couette flow in a horizontal channel are investigated. The inertialess instability regimes are studied for arbitrary wavelengths and with no simplifying requirements on the system parameters: the ratio of thicknesses of the two fluid layers; the viscosity ratio; the base shear rate; the Marangoni number $Ma$; and the Bond number $Bo$. As was established in the first part of this investigation (Frenkel, Halpern &amp; Schweiger, J. Fluid Mech., vol. 863, 2019, pp. 150–184), a quadratic dispersion equation for the complex growth rate yields two, largely continuous, branches of the normal modes, which are responsible for the flow stability properties. This is consistent with the surfactant instability case of zero gravity studied in Halpern &amp; Frenkel (J. Fluid Mech., vol. 485, 2003, pp. 191–220). The present paper focuses on the mid-wave regimes of instability, defined as those having a finite interval of unstable wavenumbers bounded away from zero. In particular, the location of the mid-wave instability regions in the ($Ma$, $Bo$)-plane, bounded by their critical curves, depending on the other system parameters, is considered. The changes of the extremal points of these critical curves with the variation of external parameters are investigated, including the bifurcation points at which new extrema emerge. Also, it is found that for the less unstable branch of normal modes, a mid-wave interval of unstable wavenumbers may sometimes coexist with a long-wave one, defined as an interval having a zero-wavenumber endpoint.

Surface-Kinetics-Limited Ostwald Ripening of Spherical Precipitates at Grain Boundaries

Ostwald ripening of sufficiently large (usually macroscopic) precipitates is the late stage of the diffusion decomposition of a supersaturated solid solution, occurring through the formation of fluctuations and subsequent growth of centers (nuclei) of a new phase. The paper describes a theoretical study of the Ostwald ripening of spherical precipitates of a newly formed phase at the grain boundary of finite thickness with the diffusion of impurity atoms from the grain interior to the grain boundary considered. The precipitate growth is assumed to be limited by the kinetics of impurity atom imbedding into the precipitate rather than by the impurity atom diffusion inside the grain boundary. The speed of diffusion growth of spherical precipitate located on the grain boundary is found. A system of equations which describes surface-kinetics-limited growth of Oswald ripening of spherical precipitates on the grain boundary is formulated. This system consists of the equation of growth rate of the precipitate, the kinetic equation for the precipitates size distribution function which is normalized by the precipitates density, and the equation of the balance of matter in the system (the law of conservation of matter). The law of conservation of matter takes into account the atoms of impurities which are in solid solutions of the grain boundary and the body of the grain as well as in the precipitates which is the specifics of our problem. The asymptotic time dependences are found for the average and critical precipitate radius, supersaturation of solid solution of impurity atoms in the grain boundary, precipitate size distribution function, precipitate density, and for the factor of grain boundary filling with precipitates (the area covered by the precipitates per unit area of the grain boundary) and the total number of impurity atoms in precipitates. The factor of grain boundary filling with precipitates is a characteristic of the two-dimensional Ostwald ripening problem. A discussion of the limits of validity of obtained results is given.

Life-time prediction for aviation GTE compressor disk based on mixed-mode and multi-axial fracture resistance parameters

This study is concerned with analysis of fatigue crack growth and life-time prediction for aviation GTE compressor disk under operation conditions. For consideration were different combinations of rotational speed, temperature, surface flaw form and sizes as well as elastic-plastic titanium alloy BT3-1 properties are employed. A crack growth rate equation is derived involving the fracture process zone size and nonlinear stress intensity factor. The assessments of the structural integrity of the rotating disk are compared for elastic and elastic-plastic solutions. It is stated that the traditional elastic crack growth models overestimate the residual fatigue lifetime with respect to the nonlinear fracture mechanics approach.

Fatigue crack growth of G20Mn5QT cast steel based on a two-parameter driving force model

This paper performs a research on fatigue crack growth in G20Mn5QT cast steel using the experimental method and a semi-empirical fatigue crack growth model. The model combines the two-parameter driving force and fatigue damage accumulation. It would take into account the effects of mean stress and load history, and the fatigue crack growth rate curve would only be influenced by the sort of material. Comparing to the experimental results, the proposed model has good simulation results. A unified fatigue crack growth rate equation for G20Mn5QT cast steel has been given out, which is more convenient for engineering applications.

Developing a method to design and simulation of a very low head axial turbine with adjustable rotor blades

Very low head (VLH) axial hydraulic turbines classified as micro-hydropower plants are capable of harvesting energy from sites with elevations below 4.5 m. The VLH turbine output power can be controlled by varying the rotational speed and the runner blade opening angles. In this paper, a design method for the VLH runner blade is developed. The numerical simulation of the designed system is presented and validated against the experimental data of an industrial prototype. The procedure is started by determining the velocity components and angles at the inlet and outlet of 2D radial sections, followed by choosing a hydrofoil for each radial section and calculating the hydrodynamic coefficients. The stagger angle and the chord-length of the section are computed using a MATLAB code coupled with XFoil. The multi-section product of 3D spherical radial sections in ANSYS TurboGrid 15.0 meshing tool forms the runner blade and the guide vane. Importing the generated structured grid into ANSYS CFX 15.0 solver, the RANS equations are solved using the SST turbulence model to capture the turbulent structures. The simplified Rayleigh-Plesset equation for bubble growth rate in the homogenous two-phase model is applied to study the cavitation phenomenon for different states of runner opening angles and rotational speeds. The maximum hydraulic efficiencies for most of the runner positions (at constant angular velocity of 40 rpm) are more than 80%. We demonstrate the effects of runner blade opening angle and the turbine rotational speed on the hydraulic efficiency curves and turbine efficiency hill chart. The cavitation simulation demonstrates leading edge and tip gap cavitation in some off-design points at different blade opening angles.

A general method to determine optimal thermal cycles based on solid-state sintering fundamentals

Most technical ceramics require processing up to and including final-stage sintering to obtain a high-density bulk while inhibiting grain growth as dominant sintering process as far as possible. The literature typically highlights the qualitative interdependence of the sintering variables and microstructural parameters, focusing on very simple particulate systems. However, a quantitative method to achieve optimum sintering of actual polycrystalline solids is still lacking.This paper puts forward such a method, which has been satisfactorily tested by the authors. The method consists of a mathematical model, based on the physical phenomena that take place during solid-state sintering. The method leads to two differential equations: a densification rate and a pore-dragged normal grain growth rate equation during final-stage sintering, which mainly depend on sintering temperature and shaping conditions. Simultaneous numerical integration of these two rate equations allows design of an optimal thermal cycle (enhancing densification and controlling grain growth) to obtain the targeted sintered polycrystalline microstructure. Application of this method yields staggered thermal cycles, in addition to the number of steps, as well as the sintering temperature and dwell time in each step.

Evaluation of topology-dependent growth rate equations of three-dimensional grains using realistic microstructure simulations

Understanding the laws of grain (or bubble, cell) growth in two and three dimensions (2D & 3D) is one of the classic and important problems in the fields of mathematics, Physics, materials sciences and biology. Studies related to the evaluation of topology-dependent grain growth rate models are very limited so far. Those who reported about the evaluation of the growth rate models used synthetic structure grain data generated from Monte Carlo–Potts model simulations. In this paper, topology-dependent growth rate models for 3D grains are evaluated by using realistic microstructure grain growth simulation data. The results show that, except Wang –Liu’s equation [H Wang and G Q Liu EPL 96, 38003 (2011)], all the other topology-dependent growth rate models have their limitations to describe the average growth rate of 3D grains, those models are not applicable for grains having number of faces less than 7; however, Yu–Liu’s equation [G Q Liu and H B Yu Chin. Sci. Bull. 41, 2000 (1996)], Glazier’s equation [J A Glazier Phys. Rev. Lett. 70, 2170 (1993)] and MacPherson–Srolovitz’s topology-dependent equation [R D Macpherson and D J Srolovitz Nature (London) 446, 1053 (2007)] fit well to the realistic simulation data for grains having number of faces greater than 7. The Wang –Liu’s equation [H Wang and G Q Liu EPL 96, 38003 (2011)] is applicable for all grains in the system and hence it is the best choice to study the average growth rate of individual grains in microstructures. The results also show that the Monte Carlo–Potts model simulations have very close correspondence with the evolution of real structures.

Precipitation and strengthening modeling for disk-shaped particles in aluminum alloys: Size distribution considered

For an ICME (Integrated Computational Material Engineering) modeling framework used for the age-hardening aluminum alloy design and heat treatment parameters optimization, it is critical to take into account the geometric shape of precipitates, as it is tightly related to the precipitation kinetics and particles' hardening effect. The aim of this paper is to present such an ICME modeling approach to describe the precipitation of disk-shaped hardening particles during aging treatment and predict the final yield strength. The classical Kampmann–Wagner Numerical (KWN) model is extended to consider the influence of disk-shaped particle morphology on growth kinetics. The extension consists of two correction factors to the growth rate equation and to the Gibbs-Thomson effect. The extended model, coupled with a metastable thermodynamic database, is applied to simulate precipitation kinetics of Al-Cu and Al-Mg-Zn alloys during aging treatment. The predicted microstructural features are in reasonable agreement with the reported experimental observations. Furthermore, a strengthening model for disk-shaped particles, which considers the size distributions of precipitates, is developed. The predicted yield strengths are compared with reported tensile test results and with predictions from other strength models. Unlike other models, the proposed strength model can reveal the strength contribution from disk-shaped precipitates without an additional tuning parameter for accounting for the impact of the mean particle spacing in the slip plane.

Crystal Growth of Salicylamide in Organic Solvents

Salicylamide was used as a model active pharmaceutical compound to investigate the crystal growth process and its associated kinetics. The impact of organic solvent, supersaturation, and temperature on the crystal growth was studied. The multiparticle crystal growth kinetics were determined using the seeded isothermal de-supersaturation method and modeled using several growth rate equations, using different representations of the driving force. The results showed that crystal growth is significantly influenced by experimental conditions. Within the range of experimental conditions, the growth kinetics was affected strongly by the temperature and to a lesser degree by solvent choice. Comparison of the growth order parameter reveals a surface integration controlled growth. Higher than expected activation energies indicate desolvation as a governing process. A comparison of the influence of the solvent on the crystal growth of salicylamide against previously published approximate data at much higher supersat...

Characterization of a Multistage Continuous MSMPR Crystallization Process Assisted by Image Analysis of Elongated Crystals

This work demonstrates how quantitative image analysis can assist in the characterization of continuous crystallization processes and in the proper selection of mathematical models for the early assessment of crystal quality. An active pharmaceutical ingredient presenting an elongated crystal habit was crystallized using two stirred tank crystallizers in series. With image analysis of the crystallization magma, the sources of crystal breakage in the crystallization cascade were identified, and the impact on crystal habit was evaluated quantitatively. As it is expected for particles presenting high aspect ratios, crystal breakage preferentially occurs in the smallest plane, perpendicular to the largest dimension. This phenomenon is hardly avoidable in downstream production, but it can be accounted for with a design approach based on the real crystal dimensions. The kinetic rate equations for nucleation and crystal growth were determined based on crystal width, from which a model for the accurate prediction...

Modeling of the in-situ nitrogen (N) doping of graphene-carbon nanotube (CNT) hybrids in a plasma medium and their field emission properties

A numerical formalism for investigating the effect of in-situ nitrogen doping (N-doping) on the plasma-assisted growth of graphene-carbon nanotube (CNT) hybrids is established. The formalism includes the energy balance on the catalyst particle and the kinetics of plasma species with contribution from hydrogen, hydrocarbon, and ammonia that aids in N-doping, for the growth of in-situ N-doped CNT, graphene, and graphene-CNT hybrids. The growth rate equations for the N-doped CNT, graphene, and graphene-CNT hybrids are also set up as a part of the model. With N-doping, the hydrogen ionic species density initially increases and then falls, promoting the growth of higher order hydrocarbons in plasma. The electron density also increases with N-doping such that the electron-mediated ionization and dissociation processes, increase eventually affecting the availability of growth precursors. The cumulative effect of the variation in the plasma species density with N-doping leads to the growth of nanostructures with a high aspect ratio. In the present work, the field enhancement factor (β) of the graphene-CNT hybrids is approximated as the ratio of its dimension along the y-axis to that along the z-axis. The β of graphene-CNT hybrids is found to be larger than that of the undoped and N-doped CNT and graphene. Moreover, N-doping further enhances the β of graphene-CNT hybrids.