Prediction Of Release Rate Research Articles

PRELIMINARY STUDY OF DEPENDENCE OF SMOKE AND CARBON MONOXIDE EMISSION ON HEAT RELEASE RATE FROM FAST-GROWING WOOD SPECIES

The aim of this paper is to create the model for prediction of carbon monoxide release rate (CORR) and smoke production rate (SPR) from heat release rate (HRR) of fast-growing wood species. The model is independent on wood species, thus is suitable for all fast-growing wood species. Three wood species hybrid poplar J-105 (Populus nigra × P. maximowiczii A. Henry), white willow (Salix alba L.) and black locust (Robinia pseudoacacia L.) were used for universal model creation. The heat release rate, smoke production rate and carbon monoxide release rate have been measured at three heat fluxes (25, 35 and 50 kW.m-2) by the cone calorimeter. The average values of CORR and SPR for all investigated wood species were 0.051 g.m-2.s-1 and 0.086 m2.m-2.s-1, respectively. Both dependencies of SPR and CORR on HRR have shown similar trends during the ignition phase (unstable trend) and during the intense burning phase (roughly linear increasing with HRR). The main difference was shown during the steady state phase (dependency of SPR on HRR is stable while dependency of CO on HRR is highly unstable). The results also proved a significant impact of wood density on these dependencies, thus, the neural network for prediction of SPR, CORR from HRR was applied. The coefficients of determination R2 for trained neural networks, for both SPR and CORR, were achieved in the range from 0.96 to 0.97

Real-time in-line prediction of drug loading and release rate in the coating process of diclofenac sodium spheres based on near infrared spectroscopy

The preparation of diclofenac sodium spheres by fluidized bed is a common production mode for the pharmaceutical preparations at present, but the critical material attributes in the production process is mostly analyzed off-line, which is time-consuming and laborious, and the analysis results lag behind. In this paper, the real-time in-line prediction of drug loading of diclofenac sodium and the release rate during the coating process was realized by using near infrared spectroscopy. For the best near infrared spectroscopy (NIRS) model of drug loading, R2cv, R2p, RMSECV, RMSEP were 0.9874, 0.9973, 0.002549 mg/g, 0.001515 mg/g respectively. For the best NIRS model of three release time points, the R2cv, R2p, RMSECV and RMSEP were 0.9755, 0.9823, 3.233%, 4.500%; 0.9358, 0.9965, 2.598%, 0.7939% and 0.9867, 0.9927, 0.4085%, 0.4726% respectively. And the analytical ability of these model was verified. The organic combination of these two parts of work constituted an important basis for ensuring the safety and effectiveness of diclofenac sodium spheres from the perspective of production process.

Diavik Waste-Rock Project, Northwest Territories, Canada: Predicting Field-Scale Waste-Rock Drainage Quality from Humidity-Cell Experiments

Abstract The prediction of water quality from waste-rock stockpiles is an important aspect of mine planning and closure. These predictions are complex, and a well-documented mechanistic approach can provide greater confidence in the results. In this study, humidity-cell experiments (1-kg sample) conducted at 5° and 22°C were used to estimate the effluent water quality and release rates of oxidation products from small-scale (12 t) field-based lysimeters. A comparison between estimated total mass loadings from laboratory humidity cells and total mass loadings from field lysimeters at the Diavik diamond mine, Northwest Territories, Canada, was completed for a five-year period. Measured temperature, S content, and surface area values were used as the primary scaling variables in these estimates. The release rate of SO42− from humidity cells with varying S content (ranging from 0.02–0.18 wt % total S) were normalized to the surface area of sulfide (mol m–2 sulfide S–1 sec–1) from each humidity cell. The resulting variability in SO42− release rates for waste-rock types were within one order of magnitude. The release rates of SO42− from the humidity cells were used to estimate the release rates from waste rock in the field with an average of 0.053 wt % total S. The results suggest that the measured annual total mass loading in the field was within the range predicted from the normalized annual total mass loadings using the surface area of sulfide from the humidity cells, with some discrepancies. Variation in annual loading at the field scale, presumably due to variability in precipitation and flushing, resulted in year-to-year discrepancies. Predictions of Fe and Ni release rates did not capture the field lysimeter results well, likely as a result of variations in geochemical conditions between laboratory and field-scale experiments (i.e., pH, mineral solubility) and also physical and geochemical heterogeneity that is not fully captured in the material characterization at each scale. The results indicate that, at this scale, annual total mass loadings can be estimated using small-scale humidity cells with a mechanistic approach if a thorough characterization of the waste rock is completed to better refine the release rates.

Experimental and Analytical Study of Temperature Swing Piston Coatings in a Medium-Duty Diesel Engine

<div class="section abstract"><div class="htmlview paragraph">The use of Thermal Barrier Coatings (TBCs) has been shown to be a promising technology to improve internal combustion engine efficiencies by reducing heat rejection to the coolant and oil. In recent studies, temperature swing coatings that have simultaneously low volumetric heat capacity and low thermal conductivity have been shown to be particularly promising in this regard. In this study, a traditional and a newer swing coating are applied to the piston of an on-road medium-duty diesel engine to assess the benefits of their use. An analytical wall temperature model is coupled to the 1-D engine simulation software GT-POWER and predictions of wall temperature, heat transfer and chemical heat release rate are presented. The swing coating is found to yield an ~1.2% efficiency benefit at the highest load condition studied alongside an 80°C improvement in exhaust temperature at the lowest load condition studied compared to a reference uncoated piston. Further, the traditional TBC was not found to have a significant efficiency advantage over the reference uncoated piston, highlighting the promise of the swing coating in improving the thermal efficiency of on-road diesel engines.</div></div>

Predicting the effect of biodiesel composition on the performance and emission of a compression ignition engine using a phenomenological model

The renewable biodiesels have been under active consideration for replacing fossil diesel due to the proximity of their properties and minimum engine hardware modifications. Biodiesels derived from fatty acids of plant or animal origin exhibit significant composition variations depending upon the feedstock used for production. The oxides of nitrogen (NOx) emission from biodiesel are higher than diesel and remain a significant concern. In the present work, combustion and nitric oxide (NO) emission characteristics of any generic biodiesel are predicted using a phenomenological modeling approach. The developed model accounts for biodiesel composition effects on physical properties, spray, auto-ignition, combustion and emission formation. The model predictions are validated with measurements done in a turbocharged multi-cylinder heavy-duty engine fuelled with two biodiesel fuels having significantly different compositions, viz. Karanja having a higher proportion of unsaturated methyl esters, and Palm having a higher proportion of saturated methyl esters. The cylinder pressure histories and peak pressures are predicted within an error of 5% and 3%, respectively. The model shows a reasonable qualitative agreement in heat release rate predictions. The NO emission is predicted within 23% error using the extended Zeldovich mechanism. The model is efficient in predicting the engine characteristics at high loads for any generic biodiesel with minimal run time (~2 min). The validated model is then used to examine the relationship between biodiesel composition and NO emission, wherein a better correlation is obtained between biodiesel composition-based parameter, viz. short-chain saturation factor (SCSF) with maximum spray temperature and NO emission.

Environmental risk assessment of using antifouling paints on pleasure crafts in European Union waters

To ensure sustainable use of antifouling paints, the European Union have developed a new environmental risk assessment tool, which a product must pass prior to its placement on the market. In this new tool, environmental concentrations are predicted based on estimated release rates of biocides to the aquatic environment and risk characterization ratios are calculated in regional spreadsheets. There are currently two methods in use to predict release rates of biocides; a calculation method and a laboratory method. These methods have been believed to overestimate environmental release of biocides and therefore fixed correction factors to reduce the release rate can be applied. An alternative method, known as the XRF method, has recently been developed and used to derive field release rates from antifouling paints. The aim of this study was to review the new environmental risk assessment tool and assess how the choice of release rate method and application of correction factors impact the approval of antifouling paint products. Eight coatings were environmentally risk assessed for usage in four European marine regions; Baltic, Baltic Transition, Atlantic and Mediterranean; by applying release rates of copper and zinc determined with the different methods. The results showed none of the coatings to pass the environmental risk assessment in the Baltic, Baltic Transition and the Mediterranean if field release rates were used. In contrast, most of the coatings passed if the correction factors were applied on the release rates obtained with the calculation or laboratory method. The results demonstrate the importance of release rate method choice on the outcome of antifouling product approval in EU. To reduce the impact of antifouling paints on the marine environment it is recommended that no correction factors should be allowed in the environmental risk assessment or preferably that site-specific field release rates are used. If the regulation in the European Union (and elsewhere) continues to allow correction factors, the pressure of biocides to the environment from leisure boating will result in degradation of marine ecosystems.

A Study on the Characteristics of FDS Heat Release Rate Predictions for Fire involving Solid Combustible Materials in a Closed Compartment

A Study on the Characteristics of FDS Heat Release Rate Predictions for Fire involving Solid Combustible Materials in a Closed Compartment

Characteristics of Heat Release Rate Predictions of Fire by a Fire Dynamics Simulator for Solid Combustible Materials

The heat release rate (HRR) of fire for solid combustibles, consisting of multi-materials, was measured using the ISO 9705 room corner test, and a computational analysis was conducted to simulate the fire using an HRR prediction model that was provided by a fire dynamics simulator (FDS). As the solid combustible consisted of multi-materials, a cinema chair composed primarily of PU foam, PP, and steel was employed. The method for predicting the HRR provided by the FDS can be categorized into a simple model and a pyrolysis model. Because each model was applied and computational analysis was conducted under the same conditions, the HRR and fire growth rate predicted by the pyrolysis model had good agreement with the results obtained using the ISO 9705 room corner test.

Advanced flow cell design for in vitro release testing of mucoadhesive buccal films.

Films for buccal application are a slowly emerging new platform for drug delivery. There remains a lack of analytical techniques for the determination of in vitro active pharmaceutical ingredient release. The aim here was to develop an alternative method to the commonly used United States Pharmacopoeia (USP) 2 method, based on the flow-through cell. This system extends the release time and enables more detailed sample discrimination according to formulation. It could be used as a tool for in vivo prediction of drug release rates from buccal film formulations. The flow cell contains two chambers separated by a membrane through which the released active pharmaceutical ingredient is measured. Vital system variables and their effects on the release rate of the model active pharmaceutical ingredient are presented for formulations based on sodium alginate polymer. The method reflects the differences between films and is shown to be discriminatory for evaluation of buccal formulations.

Applying the FDS pyrolysis model to predict heat release rate in small-scale forced ventilation tunnel experiments

The pyrolysis model in FDS6 is applied to simulate a series of small-scale tunnel experiments under varied forced ventilation velocities, where cribs made of medium density fireboard (MDF) are used as the fuel source. Prior to the simulations the material properties of MDF are investigated in order to effectively describe the decomposition behaviour in FDS6 and to develop optimised values. In the tunnel simulations, the effect of the burning duration of the ignition source, the heat of combustion of the MDF in the presence of the forced ventilation, the assumed fuel mass and the modelling domain set-up on the prediction of heat release rate are examined. It is found that the cribs take longer to ignite than that in the experiment; the available burning mass is affected by the assumed thickness of the crib sticks and the available surface area; and a limited domain size can result in not all of the fuel burning. Efforts are made to obtain an equivalent burning mass to the experiments and to account for the influence of the forced ventilation on the burning efficiency by manually specifying the heat of combustion to improve the predictions of heat release rate and consumption of fuel mass.

Relevance of formation conditions to the size, morphology and local structure of intrinsic plutonium colloids

Fundamental knowledge about plutonium intrinsic colloids is a key issue for the prediction of plutonium transport and release rates in the environment.

Nanolipogels as a cell-mimicking platform for controlled release of biomacromolecules.

We present studies of protein (insulin) efflux rates from nano-sized core–shell systems with a gelled core and a lipid bilayer (nanolipogels). The efflux control mechanism is the manipulation of mesh size, and we show that diffusion control via crosslinking is the dominant mechanism for efflux control. The concept is inspired by the macromolecular crowding effect in human cells, which may be considered as a physical network of undefined mesh size. Our bio-inspired system is made of chemically crosslinked water-swellable poly(ethylene glycol) diacrylate cores, whose mesh size can be manipulated to yield a quantifiable crowding effect that then leads to predictable release rates for biomacromolecules.

Comparative release rates from controlled release polymer coatings—comparisons between models and experiment

Controlled release devices and coatings are used heavily in widely varying applications. Here, we focus on applications to antifouling coatings by adding an active agent to polymeric coatings. Quantitative models were developed for four distinctively different methods of dispersing the active agent in the coating. The predicted release rates from these models were contrasted to reveal the inherent differences in the time-dependent release rate profiles achievable from these types of coatings. The majority of these four coatings (monolithic, dispersed particle and reservoir membrane) release the active agent with greatly varying rates over their effective lifetimes, while a microcapsule-based coating has the potential to produce relatively constant rates of release. While the models are potentially of great value, they require a number of parameters, particularly the diffusion coefficient of the active agent through the polymer, to be quantified. We demonstrate how such parameters can be quantified through release rate measurements from simple experimental coatings.

A Computational Model for Drug Release from PLGA Implant.

Due to the relative ease of producing nanofibers with a core–shell structure, emulsion electrospinning has been investigated intensively in making nanofibrous drug delivery systems for controlled and sustained release. Predictions of drug release rates from the poly (d,l-lactic-co-glycolic acid) (PLGA) produced via emulsion electrospinning can be a very difficult task due to the complexity of the system. A computational finite element methodology was used to calculate the diffusion mass transport of Rhodamine B (fluorescent drug model). Degradation effects and hydrophobicity (partitioning phenomenon) at the fiber/surrounding interface were included in the models. The results are validated by experiments where electrospun PLGA nanofiber mats with different contents were used. A new approach to three-dimensional (3D) modeling of nanofibers is presented in this work. The authors have introduced two original models for diffusive drug release from nanofibers to the 3D surrounding medium discretized by continuum 3D finite elements: (1) A model with simple radial one-dimensional (1D) finite elements, and (2) a model consisting of composite smeared finite elements (CSFEs). Numerical solutions, compared to experiments, demonstrate that both computational models provide accurate predictions of the diffusion process and can therefore serve as efficient tools for describing transport inside a polymer fiber network and drug release to the surrounding porous medium.

Optimizing Nanoparticle Design for Gene Therapy: Protection of Oligonucleotides from Degradation Without Impeding Release of Cargo.

Gene therapy delivery systems that rely on synthetic nanocarriers can be optimized by assays of nucleic acid protection and kinetic studies of nucleic acid release. These empirical measurements ensure nanoparticle stability and predict potential in vivo efficacy. Quantitative methods for assessment of the capacity of nanoparticles to protect oligonucleotide cargo and to measure the rate of release of the cargo were developed and tested based on six commercial cationic matrices. in vitro study of drug release kinetics provides predictable release rates under a variety of conditions which can be adapted to appropriate physiological factors that affect release in vivo. In brief, in vitro DNA release and DNase I degradation assays described here will be useful for optimization of nanocarrier-mediated gene therapy administration by various routes.

Numerical Study of Natural Gas/Diesel Reactivity Controlled Compression Ignition Combustion with Large Eddy Simulation and Reynolds-Averaged Navier–Stokes Model

In the current study, a comparative study is performed using Large Eddy Simulation (LES) and Reynolds-averaged Navier–Stokes (RANS) turbulence models on a natural gas/diesel Reactivity Controlled Compression Ignition (RCCI) engine. The numerical results are validated against the available research work in the literature. The RNG (Re-Normalization Group) k − ε and dynamic structure models are employed to model turbulent flow for RANS and LES simulations, respectively. Parameters like the premixed natural gas mass fraction, the second start of injection timing (SOI2) of diesel and the engine speed are studied to compare performance of RANS and LES models on combustion and pollutant emissions prediction. The results obtained showed that the LES and RANS model give almost similar predictions of cylinder pressure and heat release rate at lower natural gas mass fractions and late SOI2 timings. However, the LES showed improved capability to predict the natural gas auto-ignition and pollutant emissions prediction compared to RANS model especially at higher natural gas mass fractions.

Plant Growth and Leachate Electrical Conductivity and pH as Influenced by Controlled-release Fertilizer Blends and Coating Technologies

Although controlled-release fertilizers (CRFs) have been used in container-grown ornamental plants for decades, new coating technologies and blends of fertilizers coated for specific release rates are being employed to customize fertility for specific environments and crops. A study was conducted in the transitional climate of Kentucky to determine the nutrient release rates of three controlled-release blends of 8- to 9-month release and growth response of ‘Double Play Pink’ japanese spirea (Spiraea japonica) and ‘Smaragd’ arbovitae (Thuja occidentalis). Fertilizer 1 (16N–3.5P–8.3K–1.8Mg + trace elements) and Fertilizer 2 (18N–3.1P–8.3K–1.8Mg + trace elements) were prototype blends with different experimental polymer coatings. Fertilizer 3 was a blend of 18N–2.2P–6.6K–1.1Ca–1.4Mg–5.8S + trace elements, which combined 100% resin-coated prills with a polymer coating. Fertilizer 4 was commercially available 15N–3.9P–10K–1.3Mg–6S + trace elements. Fertilizer 3 released its nutrients earlier in the 12-week study than the other three fertilizers and resulted in lower shoot dry weight in both species. The new polymer coating technologies show promise for delivering a predicted release rate and are appropriate for container production of these woody shrubs in Kentucky. An interesting side note of this experiment was that leachate pH measurements across treatments averaged 1.2 units lower for arbovitae (6.3) than for japanese spirea (7.5) at week 12. It was assumed that chemical and/or biological reactions at the root/substrate interface in arbovitae moderated pH increases over the study.

PH-Sensitive metal-free carbon monoxide prodrugs with tunable and predictable release rates.

Carbon monoxide prodrugs with triggered release profiles are highly desirable for targeted CO delivery to minimize their untoward side-effects. Herein, we describe a series of pH-sensitive metal-free CO prodrugs which are stable under acidic conditions and yet begin to release CO in response to increases in pH with tunable and predictable release rates.

A J-integral approach in characterizing the mechanics of a horizontal crack embedded in a cantilever beam under an end transverse force

For a cantilever beam with an embedded sharp crack and subjected to an end transverse force, the J-integral approach was employed in developing analytical estimates of the energy release rate made available to the left and right crack tip. Finite element studies also revealed that mode II conditions dominate the tip regions of such a crack (Fang and Charalambides, 2015). Thus, analytical estimates of the mode II stress intensity factor dominating each of the crack tip regions are also obtained. The analytical energy release rate predictions are compared to 2-D finite elements for a broad range of crack depths and crack center location along the beam axis. Using energy considerations, rotary spring stiffness estimates employed in Charalambides and Fang (2016a,b) in the development of a four-beam model obtained. The outcomes of the methodology used in this work provide strong encouragement in extending the method to heterogeneous composite laminates containing delamination cracks and subjected to a combination of applied loadings. Given the predominately mode II nature of the crack considered, the solutions developed herein may be used in characterizing mode II interface fracture for bonded homogeneous layered beams.

An evaluation of a mass transfer rate at the boundary of different release mechanisms in complex liquid dispersion

The paper focuses on the development of the criteria for modelling mass transfer during release process at the boundary of diffusion and fragmentation in complex liquid dispersion, such as double emulsions. The proposed model for predicting release rates accounts for the effect of mass transfer resistance coupled with the emulsion structure and external release environment. The criteria of the applicability of the proposed model were formulated after verification by studies of drug release from O1/W/O2 emulsions, prepared in a Taylor–Couette flow bioreactor. It has been found that one or more mechanisms may dominate at different release stages, depending on the mixing intensity of the release medium and internal structure of double emulsions. The experimental analysis of release rates and the changes in the emulsion structure during the release process, revealed the existence of three mechanisms: (i) diffusion, (ii) diffusion and fragmentation—loss of the original structure from double emulsions to single emulsions and (iii) fragmentation. The criteria covering the diffusion release model have been formulated, as the shear rate ranges at the boundary of different mechanisms, and correspond to the values of the critical capillary numbers, which seemed to depend on the volume fraction of internal droplets of multiple emulsions.