Test Vessel Research Articles

Experimental Investigation on Corrosion Behavior of X80 Pipeline Steel under Carbon Dioxide Aqueous Conditions.

A combined steady-state and transient approach is employed to investigate the corrosion behavior of X80 pipeline steel in carbon dioxide-saturated brines. Continuous bubbling of carbon dioxide into a test vessel with 1 liter capacity is performed to simulate the flowing condition. The measurement of time-dependent open-circuit potential, polarization resistance, and electrochemical impedance spectroscopy (EIS) is conducted to interpret the evolution of dissolution processes at the corroding interface. Three distinguishing stages are observed at a temperature of 60 °C during a whole exposure of 144 h. Analyses mainly based on the consecutive mechanism show that after the first stage of the active-adsorption state, the anodic reaction is significantly retarded by the accumulation of (FeOH)ads on the iron surface, causing a sharp increase in the polarization resistance and the open-circuit potential, as well as the disappearance of the inductive loop in EIS. At the third stage, the formation of the corrosion product layer similarly reduces both the anodic and cathodic reactions, which arouses a linear increase in the polarization resistance with time and a capacitive loop in EIS but changes the open-circuit potential slightly. An increase in salinity in this study reduces the polarization resistance and enhances iron dissolution by promoting the formation and relaxation of (FeOH)ads; however, it brings little change to the developing time of the three stages obviously. At a low temperature of 20 °C, a protective product layer is not observed in carbon dioxide-saturated brine, and the dissolution of iron is mainly under activation control during the whole exposure. A notable enlarged polarization resistance and different interfacial processes are observed in an alkaline solution compared with those in acidic environments, which is deduced to be resulted from an impedance in the relaxation of (FeOH)ads by increasing pH. The observations in this study support well that the iron dissolution reaction at the initial stage exposed in carbon dioxide aqueous environments is dominant by water adsorption on the iron surface, and further investigation should be performed on the role that carbon dioxide plays in the evolution of corrosion products and the formation of a protective film on the steel surface by taking into account local water chemistry.

Rheological and Chemical Evolution of HMA and WMA Binders Based on Ageing Kinetics.

It is fundamental to predict or estimate the rheological behavioural evolutions of binders and mixture to ensure a durability service life of the whole infrastructure. This study compared the long-term ageing kinetics of hot mix asphalt (HMA) and warm mix asphalt (WMA) produced with the same base bitumen. The difference in the component was that the WMA contained 1% of Cecabase warm agent and 5.5% of water by the weight of bitumen, to obtain a large expansion ratio (47 times). Rolling thin-film oven test (RTFOT) and pressure ageing vessel (PAV) laboratory ageing were carried out on the binder with or without the warm agent. The oven ageing procedure was conducted on the loose HMA and WMA mixtures for 0, 3, 6, and 9 days. Research results indicated that the dual effect of the studied warm agent and the foaming water sharply decreased the viscosity of the binder at a high temperature. Compared with the HMA, the warm agent improved the ageing resistance of the asphalt binder. However, higher content, such as 5.5 wt.%, of foaming water deteriorated viscosity due to a thinner bitumen film, which was more susceptible to oxidation. Therefore, less than 2 wt.% of warm agent and foaming water was recommended in the foamed WMA preparation.

Interlaboratory Validation of Toxicity Testing Using the Duckweed Lemna minor Root-Regrowth Test.

Simple SummaryDuckweed (Lemna minor) is commonly used as a phytotoxicity test organism, adopted by the main international standardization organizations (ISO, OECD, USEPA, ASTM). For duckweed tests, measurements of fronds or biomass are usually preferred with a standard exposure period of at least 7 days. The proposed root- regrowth test differs from other internationally standardized methods in several important aspects: (a) the test can be performed within 72 h; (b) the test vessel was a 24-well cell plate; (c) the required volume of test water samples was 3 mL; (d) roots were excised before exposure and newly developed roots then measured. The validation of the new test method by interlaboratory comparison tests confirmed that the Lemna root bioassay is valid and reliable. The root growth test is therefore a valuable tool for rapid toxicity screening of wastewater effluents and hazardous pollutants in natural waters because it is simple to perform, quick to conduct, cost-effective to operate, and can have operational benefits for testing time, since management decisions need to be made promptly in the event of unpredictable pollution events.The common duckweed (Lemna minor), a freshwater monocot that floats on the surfaces of slow-moving streams and ponds, is commonly used in toxicity testing. The novel Lemna root- regrowth test is a toxicity test performed in replicate test vessels (24-well plates), each containing 3 mL test solution and a 2–3 frond colony. Prior to exposure, roots are excised from the plant, and newly developed roots are measured after 3 days of regrowth. Compared to the three internationally standardized methods, this bioassay is faster (72 h), simpler, more convenient (requiring only a 3-mL) and cheaper. The sensitivity of root regrowth to 3,5-dichlorophenol was statistically the same as using the conventional ISO test method. The results of interlaboratory comparison tests conducted by 10 international institutes showed 21.3% repeatability and 27.2% reproducibility for CuSO4 and 21.28% repeatability and 18.6% reproducibility for wastewater. These validity criteria are well within the generally accepted levels of <30% to 40%, confirming that this test method is acceptable as a standardized biological test and can be used as a regulatory tool. The Lemna root regrowth test complements the lengthier conventional protocols and is suitable for rapid screening of wastewater and priority substances spikes in natural waters.

Chemical, Physical, and Rheological Evaluation of Aging Behaviors of Terminal Blend Rubberized Asphalt Binder

Terminal blend rubberized asphalt (TBRA) is widely used as binder of asphalt mixtures due to its technical characteristics of storage stability. However, its road performance deteriorates due to the aging process of TBRA. The purpose of this study is to evaluate the aging characteristics of TBRA binders containing 0%, 5%, 10%, 15%, and 20% content of crumb rubber (CR) by weight of the neat binder. All the binders were treated with rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV), respectively. The chemical compositional changes were monitored by attenuated total reflection (ATR)-Fourier transform infrared spectroscopy (FTIR), and physical and rheological properties were tested on neat asphalt and TBRA binders. FTIR test results show that TBRA binders offer greater long-term aging resistance than the neat asphalt binder, and E10TB (10% by weight CR) exhibits the highest long-term aging resistance. With the increase of CR, the temperature sensitivity property of the TBRA binders increases, whereas their high-temperature stability decreases. After PAV aging, blending CRs into neat asphalt causes a higher phase angle aging index and Jnr aging index, and lower critical temperature aging index, complex modulus aging index, softening point increment, and rutting factor aging index, indicating their superior long-term aging resistance. Moreover, based on the correlation analysis, the critical temperature aging index (CTAI) has a good linear relationship with the physical aging index (SPI) and chemical aging index (ΔICA).

Brain Perfusion and Hemodynamic Changes in Moyamoya Disease

Moyamoya disease (MMD) – is a chronic progressive disorder of the unknown etiology with the development of the critical stenoses in internal carotid arteries and abnormal vascular net formation at the basal cerebrum to compensate the hemodynamic insufficiency and further development of the ischemic attacks, strokes, hematomas. The objective: to study the cerebral hemodynamic parameters and brain perfusion in patients with moyamoya disease. Materials and methods. We performed retrospective analysis of the cerebral angiography and cerebral perfusion investigations results of 6 patients with moyamoya desease, who were hospitalized in the State Institution «Romodanov Neurosurgery Institute of NAMS of Ukraine» in 2016–2020. All patients underwent a comprehensive examination, which included neuropsychological testing, the head and neck vessels duplex scanning, multispiral computed tomography (MSCT), selective cerebral angiography (SCA), and MSCT-angiography. The assessment of myamoya vessels was done by the Suzuki angiographic scale. Cerebral hemodynamics was studied by perfusion MSCT (PMSCT). Results. The diagnosis of moyamoya desease was confirmed in all patients by SCA and MSCT angiography. The clinical manifestation of the disease was represented by ischemic (n=5; 83.3%) and hemorrhagic (n=1; 16.7%) strokes. Stage 3, Stage 4 and Stage 6 has been diagnosed by Suzuki angiographic scale. Changes of the cerebral perfusion were more significant at Stage 4 / Stage 6: CBV was increased up to 20%, CBF was decreased &gt; 30% with MTT time &gt; 6 sec. The most significant changes were founed ipsilaterally in the territories of the MCA, moderate – in the territories of the ACA and PCA. Conclusion. In patients with moyamoya disease we have found the restructuring of the cerebral angioarchitectonics which has been matching the decrease of cerebral perfusion. Perfusion MSCT allows to get identification of the areas with an increased risk of ischemia and provides a decisive quantitative assessment of cerebral hemodynamics changes to establish indications for surgical treatment.

Sensitivity of Earthworm (Eisenia fetida) in Mining Soil from Ijero-Ekiti, Nigeria

Excavation and processing of mineral deposits are valuable revenue sources yet they contribute serious environmental problems worldwide. Mining activities are widespread and contribute to heavy metal contamination in rural communities in Ekiti State, Nigeria. Available research failed to establish how mining soil may impact on resident terrestrial organisms. This study assessed the health of soil from active mining site by testing it on earthworms (Eisenia fetida) for 10 weeks. Survival, mobility, morphology and behaviour of worms were assessed while soil was analyzed for selected heavy metals by atomic absorption spectrometry. Worm survival was evident as the proportion of reference soil increased in exposure mixture and improved until 92% in the control. Worms curled up at the bottom of test vessels with varying proportions of mining site soil and appeared discolored and dehydrated when taken out of test soil, with characteristic sluggishness, particularly as the proportion of mining soil increased in exposure mixtures. Though metal levels were within permissible limits, morphology of exposed worms were visibly impacted, which corresponds in severity with increasing proportion of mining soil. On the contrary, worms tested in 100% reference soil appeared healthy and active in upper part of exposure vessels. These results suggest that the tested mining soil had adverse impacts on mobility, morphology, behavior and survival of exposed organisms when compared with the control population. Therefore, food products grown downstream of the mining site may be at risk of heavy metal contamination with consequences on food quality, water quality and food chain.

Evaluation of the Aging of Styrene-Butadiene-Styrene Modified Asphalt Binder with Different Polymer Additives.

A wide variety of polymer additives have been widely used in recent years. However, the effect of different polymer additives on the durability of asphalt binders has not been investigated thoroughly. To evaluate the aging property of styrene-butadiene-styrene (SBS) asphalt binder with different polymer additives, three polymer modifiers, namely high modulus modifier (HMM), anti-rutting agent (ARA), and high viscosity modifier (HVM), were added to it. First, the Thin Film Over Test (TFOT) and Pressure Aging Vessel (PAV) was performed on the asphalt binders. The rheological properties of the four asphalt binders before and after aging were then checked by the Dynamic Shear Rheometer Test (DSR). The chemical compositions of the asphalt binders were determined by the Fourier Transform Infrared Spectrometer (FTIR) test. Several aging indicators were adopted to reflect the aging degree of the asphalt binders. The results show that when polymer additives are added to the SBS asphalt binder, the complex modulus, storage modulus, loss modulus, and rutting factor substantially increase and the phase angle decreases. All the test parameters become higher after aging. The phase angle of the SBS asphalt binder is the highest at both unaged and aged states, while its other parameters values are the smallest. Moreover, the Carbonyl Aging Indicator (CAI) of SBS with polymer additives becomes lower under both TFOT and PAV conditions, indicating that polymer additives can improve the aging resistance of SBS asphalt, of which HVM modifies the aging resistance best. Complex Modulus Aging Indicator (CMAI) and Storage Modulus Aging Indicator (SMAI) have the best correlation coefficients with CAI, and the two aging indicators can be used to predict the aging degree of polymer modified asphalt binders.

Compliant vascular models 3D printed with the Stratasys J750: a direct characterization of model distensibility using intravascular ultrasound

PurposeThe purpose of this study is to evaluate biomechanical accuracy of 3D printed anatomical vessels using a material jetting printer (J750, Stratasys, Rehovot, Israel) by measuring distensibility via intravascular ultrasound.Materials and methodsThe test samples are 3D printed tubes to simulate arterial vessels (aorta, carotid artery, and coronary artery). Each vessel type is defined by design geometry of the vessel inner diameter and wall thickness. Vessel inner diameters are aorta = 30mm, carotid = 7mm, and coronary = 3mm. Vessel wall thickness are aorta = 3mm, carotid = 1.5mm, and coronary = 1mm. Each vessel type was printed in 3 different material options. Material options are user-selected from the J750 printer software graphical user interface as blood vessel wall anatomy elements in ‘compliant’, ‘slightly compliant’, and ‘rigid’ options. Three replicates of each vessel type were printed in each of the three selected material options, for a total of 27 models. The vessels were connected to a flow loop system where pressure was monitored via a pressure wire and cross-sectional area was measured with intravascular ultrasound (IVUS). Distensibility was calculated by comparing the % difference in cross-sectional area vs. pulse pressure to clinical literature values. Target clinical ranges for normal and diseased population distensibility are 10.3-44 % for the aorta, 5.1-10.1 % for carotid artery, and 0.5-6 % for coronary artery.ResultsAorta test vessels had the most clinically representative distensibility when printed in user-selected ‘compliant’ and ‘slightly compliant’ material. All aorta test vessels of ‘compliant’ material (n = 3) and 2 of 3 ‘slightly compliant’ vessels evaluated were within target range. Carotid vessels were most clinically represented in distensibility when printed in ‘compliant’ and ‘slightly compliant’ material. For carotid test vessels, 2 of 3 ‘compliant’ material samples and 1 of 3 ‘slightly compliant’ material samples were within target range. Coronary arteries were most clinically represented in distensibility when printed in ‘slightly compliant’ and ‘rigid’ material. For coronary test vessels, 1 of 3 ‘slightly compliant’ materials and 3 of 3 ‘rigid’ material samples fell within target range.ConclusionsThis study suggests that advancements in materials and 3D printing technology introduced with the J750 Digital Anatomy 3D Printer can enable anatomical models with clinically relevant distensibility.

Laboratory evaluation of the properties of high-cured crumb rubber modified asphalt containing sulfur and polymer after the oxidative aging procedure

The crumb rubber modified asphalt (CRMA) prepared by terminal blend (TB) process with high interaction temperature (260 °C) and extended curing time (6 h) is called high-cured CRMA, which has the characteristics of good storage stability and easy construction. The composition of the material has an important influence on the performance of high-cured CRMA after the oxidative aging procedure. In this study, the properties of high-cured CRMA containing sulfur and styrene–butadiene–styrene (SBS) after the oxidative aging procedure were studied. All binders were aged using rolling thin film oven test and pressure aging vessel, respectively. Fluorescence microscopy tests and rheological property tests of all binders were performed. The chemical composition of all binders was monitored using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy. Fluorescence microscope observation shows that the particles of the SBS phase are significantly reduced and their distribution becomes uniform with the increase of the sulfur content in the high-cured crumb rubber hybrid binder before aging. Besides, the SBS phase in high-cured crumb rubber hybrid binder gradually decreases and the distribution becomes more uniform after aging. 0.3% sulfur has a certain effect on the rutting resistance of high-cured crumb rubber hybrid binder before aging, while low sulfur content has little effect on the rutting resistance. Moreover, sulfur can retard the growth of carbonyl groups of high-cured crumb rubber hybrid binder, and improve the resistance to thermal oxidation in the rheological indexes of high-cured crumb rubber hybrid binder.

CFD Simulations of the Effect of Dust Diameter on the Dispersion in the 1 m3 Explosion Vessel

There are at least two main requirements for repeatable and reliable measurements of flammability and explosibility parameters of dusts: a uniform dispersion of solid particles inside the test vessel and a homogeneous degree of turbulence. Measurements of these parameters are performed in spherical vessels (20 L sphere or 1 m3 sphere). In several literature works, it has been shown that, in the standard 20 L sphere, the dust injection system generates a non-uniform dust cloud, while high gradients characterize the turbulent flow field. In our recent work, CFD simulations of flow field and dust concentration distribution in the 1 m3 spherical vessel were carried out and the results compared to the data previously obtained for the 20 L. It has been found that in the 1 m3 vessel, the spatial distribution of the turbulent kinetic energy is lower and much more uniform. Concerning the dust distribution, as in the case of the 20 L, dust is mainly concentrated at the outer zones of the vortices generated inside the vessel. In this work we use the previously validated CFD model to simulate the dust dispersion inside the 1 m3 vessel at different dust diameters. Results show that on increasing the dust diameter, the dust paths are different from those of the fluid flow until the sedimentation effect prevails and the turbulence field becomes similar to the dust-free air case. Since the spatial distribution of the turbulent kinetic energy is lower and much more uniform than in the 20 L sphere, the 1 m3 vessel is less susceptible to variations in the dust intrinsic properties, making parameter measurements more reliable and repeatable.

Modeling Nanosecond-Pulsed Spark Discharge and Flame Kernel Evolution

Abstract Dilute combustion, either using exhaust gas recirculation or with excess air, is considered a promising strategy to improve the thermal efficiency of internal combustion engines. However, the dilute air-fuel mixture, especially under intensified turbulence and high-pressure conditions, poses significant challenges for ignitability and combustion stability, which may limit the attainable efficiency benefits. In-depth knowledge of the flame kernel evolution to stabilize ignition and combustion in a challenging environment is crucial for effective engine development and optimization. To date, a comprehensive understanding of ignition processes that result in the development of fully predictive ignition models usable by the automotive industry does not yet exist. Spark-ignition consists of a wide range of physics that includes electrical discharge, plasma evolution, joule-heating of gas, and flame kernel initiation and growth into a self-sustainable flame. In this study, an advanced approach is proposed to model spark-ignition energy deposition and flame kernel growth. To decouple the flame kernel growth from the electrical discharge, a nanosecond-pulsed high-voltage discharge is used to trigger spark-ignition in an optically accessible small ignition test vessel with a quiescent mixture of air and methane. Initial conditions for the flame kernel, including its thermodynamic state and species composition, are derived from a plasma-chemical equilibrium calculation. The geometric shape and dimension of the kernel are characterized using a multi-dimensional thermal plasma solver. The proposed modeling approach is evaluated using a high-fidelity computational fluid dynamics procedure to compare the simulated flame kernel evolution against flame boundaries from companion Schlieren images.

Laboratory and field ageing of SBS modified bitumen: Chemical properties and microstructural characterization

Styrene-butadiene-styrene (SBS) modified bitumen is a widely-used civil engineering material with a variety of applications. The properties and durability of bitumen greatly depend on its chemical composition. Due to its organic nature bitumen is highly prone to oxidation. The main cause of bitumen oxidation is the interplay of sunlight (photo-oxidation), atmospheric oxidation with reactive oxygen species (ROS), mechanical ageing and thermal oxidation. However, current standardized ageing methods, such as rolling thin film oven test (RTFOT) and pressure ageing vessel (PAV) do not include photo-oxidation and lack realistic ageing simulation. In this work, different laboratory aging procedures like PAV, RTFOT and UV radiation are applied to SBS modified binder. At the same time field aged bitumen with 19 years service in the road is analysed. The surface has been treated with UV radiation and ROS, resulting in deformation of surface microstructures and change in chemical composition. Since ageing mainly affects the surface of bitumen, a layer study on field aged bitumen samples was conducted to demonstrate ROS penetration depth. Fluorescence spectroscopy indicated that the ROS penetration mainly affected the first centimetres of the surface and a rapid decrease of ROS diffusion could be discovered. Fluorescence excitation-emission matrix (FEEM) results show that the overall fluorescence intensity decreases with ageing. The link between chemical and morphological change due to ageing could be given with fluorescence microscopy. The colloidal nature of bitumen exerts in the microstructural composition, which undergoes undergo a major chemical and morphological change with progressive ageing. We recorded the first fluorescence image of the typical surface microstructures with previously unattainable resolution with fluorescence microscopy, highlighting fluorescing Catana and Peri phase of the surface domains while Para phase exhibited less fluorescence intensity. The link between chemical and morphological change could be given with atomic force microscopy (AFM). Finally, AFM and fluorescence microscopy indicated that photo-oxidation promoted a gradual deformation of the chemically inhomogeneous surface structures toward shrink in size, deformation of the catana pattern and a drastic increase in microstructure height compared to neat bitumen, which encourages the importance of inclusion of atmospheric photo-oxidation to standardized bitumen testing methods. • Ageing trends of 19 years field aged unaged and laboratory aged bitumen. • Gradual decrease of reactive oxygen penetration depth into the bulk material. • Photooxidation causes major structural and chemical changes on the surface features. • Fluorescence microscopy demonstrates fluorescing catana and peri phase.

Exploring the oxidative mechanisms of bitumen after laboratory short- and long-term ageing

Understanding the fundamental mechanisms of oxidative ageing in bitumen is considered of paramount importance in order to take steps towards durable binders able to tackle distresses related to this phenomenon which deteriorates the asphalt performance. This paper focuses on the identification of the intermediate and final oxygenated products after short- and long-term laboratory ageing simulated with rolling thin-film oven testing (RTFOT) and pressurised ageing vessel (PAV) respectively. Three binders were investigated in this study, two originated from the same wax-free crude source, while the third was obtained from a different source, containing natural wax, and followed a different manufacturing process. Fourier-Transform Infrared (FTIR) spectroscopy demonstrated a clear increase of the sulfoxide and carbonyl functional groups upon ageing for all the binders independently of origin, manufacturing or performance. Electron Paramagnetic Resonance (EPR) spectroscopy showed an increase of the organic carbon-centred radicals after short-term ageing (RTFOT), whereas after PAV these radicals remained constant in the two wax-free binders originating from the same crude source, and even decreased for the third, waxy binder. Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy reported differences in the relative distribution of protons between the binders in the unaged state, and similar minor changes after both ageing steps regardless of the binder’s crude source and distillation. The results of Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) revealed that SOx- and (OH)x-containing compounds are produced after the sequentially occurring short- and long-term ageing in both wax-free bitumens, whereas an almost constant behaviour of aliphatics after PAV ageing can be seen for the same bitumens. Finally, the strengths and weaknesses of each of these experimental techniques were reviewed and compared versus the obtained results and possible ageing mechanisms.

On the pyrotechnic ignitors role in dust explosion testing: Comparison between 20 L and 1 m3 explosion vessels

AbstractSeveral phenomena (e.g., initial turbulence level, overdriving, underdriving, etc.) affect the measurement of dust explosion parameters in the 20 L and 1 m3 standard test vessels. Estimating the role of each phenomenon is crucial to understand the discrepancies observed over the years between the data collected using these vessels. In this work, we focus on the role of the pyrotechnic ignitors on the pressure trend and the temperature distribution. We run explosion tests in the 20 L vessel to measure the pressure–time history generated by the explosion of pyrotechnic ignitors. Moreover, we performed CFD simulations to simulate the spatial/temporal evolution of the temperature map from the hot core due to the igniter explosion toward the vessel walls. The explosion of the pyrotechnic ignitors shows a significant increase of pressure in the 20 L vessel, suggesting that flame propagation is occurring inside the vessel. Furthermore, the localized increase of temperature due to the ignitor explosions, diffuse, and then uniformize much more rapidly in the 20 L vessel than in the 1 m3 vessel. The flame propagation generated by the ignitors is very relevant in the 20 L sphere leading to the overdriving phenomenon. This result justifies the fact that for many organic dusts, the deflagration index values measured in the 20 L are much higher than those measured in the 1 m3 vessel. CFD simulations show that the hot core generated by the ignitors dissipate much faster in the 20 L vessel than in the 1 m3 vessel, due to the higher turbulence level of the smaller vessel. Therefore, dusts whose combustion is controlled by particle heating are more prone to sustain combustion in the 1 m3 than in the 20 L vessel.

Comparative Study of Thermal-Oxidative Aging and Salt Solution Aging on Bitumen Performance.

The aging of bitumen is detrimental to the durability and service life of asphalt pavement. Previous studies found that bitumen was suspected to be aged by not only thermal oxidation but also solution immersion. This research aims to compare the effect of thermal-oxidative aging and salt solution aging on bitumen performance. For this purpose, a thin film oven test (TFOT) and pressure aging vessel aging (PAV) were selected as thermal-oxidative aging, and 10% NaCl aging and 10% CaCl2 aging were selected as salt solution aging. The morphology, oxygen content, physical properties, low-temperature properties, and high-temperature properties of bitumen were analysed by employing scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), physical tests, a bending beam rheometer (BBR), and a dynamic shear rheometer (DSR). Test results show that both thermal-oxidative aging and salt solution aging had similar influencing trends in the oxygen content, physical, low-temperature, and high-temperature properties of bitumen but had different changes in morphology. The aging degrees caused by four kinds of aging methods were obtained based on the summed values of the absolute aging factor of all parameters: PAV > 10% NaCl > TFOT > 10% CaCl2. The conclusions could provide a theoretical basis to establish a standard for the solution aging of bitumen.

Simple bicarbonate buffer system for dissolution testing: Floating lid method and its application to colonic drug delivery system

In this study, we developed a simple and easy method to use bicarbonate buffer solutions for dissolution tests. A floating lid was newly introduced to prevent the evaporation of CO2 from bicarbonate buffer solutions (the floating lid method). This method was used to evaluate the dissolution profiles of 5-aminosalicylic acid (5-ASA) colonic delivery tablets with a pH-sensitive film coating (5-ASA CDT) (Asacol® 400 mg tablet and the generic products A and B). A sodium bicarbonate solution was added to the dissolution test vessel, covered with the floating lid made of foamed styrol, and adjusted to each pH with an HCl solution (total 500 mL, 2–50 mM, pH 6.0 to 7.5). Without the floating lid, the pH value increased by more than one pH unit within 3.5 h. The floating lid suppressed the increase in pH to less than 0.1 pH unit at 3.5 h and 0.7 pH unit at 22 h. According to the drug product information, all 5-ASA CDTs show similar disintegration times (approximately 0.5 h) and release profiles in the diluted McIlvaine buffer (pH 7.5, 50 mM phosphate, 25 mM citrate). However, in the bicarbonate buffer (pH 7.5, 10 mM), the disintegration time was prolonged to 4.3 h for Asacol®, 8.0 h for generic A, and 7.6 h for generic B. The floating lid method would be useful for formulation development.

A comparison of standard test methods for determining the laboratory effectiveness of oil spill dispersants: their benefits and drawbacks

A comparison of two standard test methods for determining the laboratory effectiveness of oil spill dispersants — ASTM F2059-17 «Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Swirling Flask» and ASTM F3251-17 «Standard Test Method for Laboratory Oil Spill Dispersant Effectiveness Using the Baffled Flask» — is presented in this article. It is underlined that ASTM F2059-17 and ASTM F3251-17 are almost identical from the methodological and technical points of view. The main differences lie in specific design features of the applied test vessels and mixing energies created inside them. It is reasonably established that ASTM F2059-17 can be defined as a low-energy, but ASTM F3251-17 — as a high-energy laboratory test method. The specific examples of application of the test methods for determining the effectiveness of commercially available dispersants are given. It is also concluded that both test methods are necessary to apply for a correct understanding of the dispersant effectiveness. Herewith, the results obtained according to ASTM F2059-17 should be conditionally considered as the lower limit and those according to ASTM F3251-17 — the upper limit of effectiveness of the dispersant. Moreover, the use of gas chromatography with flame ionization detection (GC-FID) is emphasized to be sometimes impossible as a recommended in both ASTM F2059-17 and ASTM F3251-17 method for analyzing the oil extracts obtained during the test. The UV spectrophotometry is proposed instead of GC-FID as an alternative. However, its application is possible only after mandatory optimization of the measurement parameters for each specific oil.

Reliability analysis of deepwater explosion test vessel based on dynamic prediction

A deep-water explosion test vessel is an important test equipment which is filled with water to simulate different water depth environment by loading different hydrostatic pressure, and it can be used to study deep water explosion theory and engineering technology based on the similarity principle. In order to ensure the safety of vessels used in deep-water explosion test, a random-interval dynamic reliability model based on intelligent prediction is proposed in this paper. A GRNN prediction network of vessel response is established through dynamic test data, and the maximum strain interval variable of the vessel is obtained. Considering the random characteristics of the vessel structure, the reliability analysis of the in-service deep-water explosion test vessel is carried out. During the period, three methods are used to calculate the reliability index, and the analysis shows that for the vessel structure with high reliability and lack of sample data, the hybrid reliability model based on dynamic prediction is established by the calculation of interval reliability index. The method is simple and feasible. At the same time, the interval variables of the model change with the structural dynamic test data, and the uncertainty analysis of the structure is also dynamic. Therefore, the reliability of the container obtained is also changing with the service process, and has dynamic characteristics, which can better reflect the performance changes of the container during the service period and provide the basis for the use and maintenance decision of the container.

Effect of Aging on the Rheological and Molecular Weight Distribution of Asphalt Binder Treated with Polyphosphoric Acid

Asphalt binder behaves as a viscoelastic material and its inherit performance is dominated by rheological and chemical properties. Aging of asphalt binder is a prominent distress for long‐term in‐service asphalt pavement. In this work, the effect of aging on base asphalt modified by polyphosphoric acid (PPA) has been investigated. For the objective, virgin asphalt binder was modified by various dosages of PPA, styrene‐butadiene‐styrene (SBS), and PPA/SBS compound modification. The short‐ and long‐term aging processes were simulated by Rolling Thin‐Film Oven Test (RTFOT) and Pressure Aging Vessel (PAV) procedure. Rheological property of five aged modified binders was evaluated by the Dynamic Shear Rheometer (DSR). Meanwhile, gel permeation chromatography (GPC) was conducted to measure the molecular weight distribution and dispersion coefficient during the aging process. The high‐temperature stiffness of PPA polymer binders is slightly higher than that of SBS and PPA/SBS compound modified asphalts. The aging ratio and molecular weight analysis verify the lower thermal‐oxidative susceptibility of PPA/SBS compound modified asphalts. This study offers an understanding for the promotion and application of PPA modifier.

Breakdown Voltage of Transformer Oil Containing Cellulose Particle Contamination With and Without Bridge Formation Under Lightning Impulse Stress

This study investigates the effect of cellulose bridge formation on insulating oil. Such effect influences the breakdown voltage and strength of mineral oil (MO) under standard lightning impulse (LI) voltage. A cylindrical test vessel fitted with spherical–spherical electrodes with a 2 mm gap distance between them was used to generate a quasi-uniform field and observe bridge formation between the gaps. A positive LI waveform (1.2/ $50~\mu \text{s}$ ) generated by an impulse generator was applied during the breakdown tests. The rising-voltage method was used to measure the breakdown voltage in accordance with the IEC 60897 standard test method. Weibull cumulative breakdown probability was applied to present the breakdown results statistically, and the outcome was compared with clean oil (CO). Commercial cellulose microcrystalline particles were dispersed into the transformer oil to act as bridge. The concentrations of the samples were 0.004%, 0.008% and 0.012% by weight. The breakdown test results showed that the cellulosic particles reduced the LI breakdown voltage (LIBV) of MO by up to 10%. The influence of cellulose particles on LIBV was also more prominent during bridge formation, with a further reduction of 14%. Evidently, the presence of the cellulose bridge exerted a detrimental effect on the breakdown voltage of MO under LI stress, yielding a reduction of 24% and 27% at 0.004 wt% and 0.012 wt%, respectively. Finite element analysis also indicated that the electrical field strength of cellulosic particle contamination of 0.004 wt% and 0.012 wt% without a bridge skeleton exceeded the critical electric field strength of CO by 20% and 61%, respectively. The presence of cellulosic contamination at any concentration, i.e. either with or without a bridge structure, clearly decreased the breakdown strength of transformer oil. However, the breakdown is not occurred instantaneously. The LI breakdown was initiated and established only at a certain impulse stress level, when the electric field strength along the bridge lines exceeded the critical electric field strength of the oil. Thus, this finding potentially contributes to the formulation of guidelines for condition assessment and contamination monitoring to minimise common issues in power transformer failures that are attributable to the insulation system, and consequently, achieve optimum transformer insulation integrity.