Steady-state Method Research Articles

Measuring gas permeability in tight cores at high pressure: Insights into supercritical carbon dioxide seepage characteristics.

This study introduces a new, more accurate instrument for measuring gas permeability in tight cores at high pressure, surpassing the accuracy of conventional methods. Using the steady-state method, the study tested the permeability of carbon dioxide (CO2) in tight cores at various pressure conditions. We observed that, similar to nitrogen, CO2 permeability initially conformed to the Klinkenberg slip theory, but began to deviate as back pressure increased. Supercritical CO2 exhibited a slight increase in permeability, which contrasts with both nitrogen behavior and the Klinkenberg slip theory. Accurate measurement of CO2 permeability in tight rocks is crucial for assessing the feasibility and efficiency of CO2 injection and storage, which could help reduce greenhouse gas emissions and drive energy transformation. The innovative measurement approach can assist in identifying the ideal production pressure drops, injection pressures, and flow rate parameters, thus improving the recovery rate of tight oil reservoirs. Nevertheless, the study had some limitations, including prolonged stable flow time, lack of real-time flow rate display, and reliance on theoretical viscosity calculations, all of which could affect the accuracy of permeability measurements. Further research is needed to investigate CO2 permeability under diverse conditions and to deepen our understanding of CO2 transport and storage in tight cores, which could lead to improvements in CO2 sequestration and the efficiency of enhanced oil recovery.

Kinetic and structural characterization of carboxyspermidine dehydrogenase of polyamine biosynthesis

Polyamines are positively charged alkylamines ubiquitous among eukaryotes, prokaryotes, and archaea. Humans obtain polyamines through dietary intake, metabolic production, or uptake of polyamines made by gut microbes. The polyamine biosynthetic pathway used by most gut microbes differs from that used by human cells. This alternative pathway employs carboxyspermidine dehydrogenase (CASDH), an enzyme with limited characterization. Here, we solved a 1.94Å X-ray crystal structure of Bacteroides fragilis CASDH by molecular replacement. BfCASDH is composed of three domains with a fold similar to saccharopine dehydrogenase but with a distinct active site arrangement. Using steady-state methods, we determined kcat and kcat/Km for BfCASDH and Clostridium leptum CASDH using putrescine, diaminopropane, aspartate semi-aldehyde, NADH, and NADPH as substrates. These data revealed evidence of cooperativity in BfCASDH. Putrescine is the likely polyamine substrate and NADPH is the coenzyme used to complete the reaction, forming carboxyspermidine as a product. These data provide the first kinetic characterization of CASDH-a key enzyme in the production of microbial polyamines.

Bodipy−corrole tetrads as heavy−atom−free triplet photosensitizers: Study of the energy transfer and application in triplet−triplet annihilation upconversion

Free base corrole can generate triplet state without invoking of heavy−atom effect, however, its weak and narrow absorption band in the visible spectral range make corrole not an ideal triplet photosensitizer. Herein, novel Bodipy−corrole tetrads were prepared by attaching visible light-harvesting antennae of Bodipy or electron spin converter with fullerene units (2B−Tur−Cor and B−C60−Tur−Cor) to solve the above problems, which show a stronger and broader absorption band in the visible region, and the maximum molar absorption coefficient is up to 2.58 × 105 M−1 cm−1 at 504 nm for 2B−Tur−Cor. By using of fluorescence spectroscopy, steady-state and time-resolved transient absorption spectroscopic methods, the singlet energy transfer progress from the Bodipy moiety to the corrole moiety was confirmed. Through fluorescence lifetimes and fluorescence excitation spectrum study, the rate constant of the singlet energy transfer was calculated as 9.58 × 107 s−1 for 2B−Tur−Cor and 2.45 × 108 s−1 for B−C60−Tur−Cor, respectively. The TD−DFT computation suggests that the first and second triplet state is localized in the corrole moiety and the Bodipy moiety for 2B−Tur−Cor, respectively, and the triplet state energy was calculated to be 1.37 eV and 1.61 eV, respectively. Nanosecond time−resolved transient difference absorption spectra show that the triplet excited states of these tetrads are localized on corrole unit, the lifetime of 2B−T−Cor is up to 143 μs, however, the lifetime of B−C60−Tur−Cor is only 3.3 μs. Long-lived triplet excited states play important role in applications of the triplet photosensitizers in photocatalysis or other photophysical processes concerning triplet–triplet−energy−transfer. As a proof of concept, these tetrads were used as heavy−atom−free organic triplet photosensitizers for triplet−triplet annihilation based upconversion. The upconversion quantum yield was up to 5.86% for 2B−Tur−Cor, however, it is only 0.52% for B−C60−Tur−Cor.

Detailed physicochemical study and thermodynamic aspects of the interaction between nonionic cellulose derivative hydroxyethyl cellulose and anionic surfactant sodium N-dodecanoyl sarcosinate in aqueous media

BackgroundThe scheme of this work was to study the interaction between hydroxyethyl cellulose (HEC), a non-ionic, water soluble biopolymer and sodium N-dodecanoyl sarcosinate (SDDS), a novel, environmentally friendly amino acid-based anionic surfactant in aqueous medium. The study of this type of interaction is relatively less complicated compared to that between a polymer and a surfactant with opposite charges. MethodsThe critical micelle concentration (CMC) of HEC-induced SDDS has been determined by various physicochemical methods such as tensiometry, conductometry, fluorimetry and microcalorimetry. Several thermodynamic and surface parameters related to the binding of SDDS with HEC have been assessed. The aggregation number (Nagg) of SDDS micelles in the presence of non-ionic HEC polymer has been measured by the steady-state fluorescence method. The hydrodynamic diameter (Dh) and zeta potential (ζ) of the polymer-surfactant aggregate have been measured by the dynamic light scattering method. The interaction study has further been amplified by detecting the change in the surface morphology of the polymer due to surfactant binding using Field Emission Scanning Electron Microscopy (FESEM) and high resolution transmission electron microscopy (HR-TEM) imaging in solvent-free state, as well as visualization of the HEC-SDDS micelle in the solution phase using fluorescence microscopy technique. Significant findingsFrom a physicochemical point of view, hydrophobic synergism seems to be important for understanding the interaction pattern of HEC-SDDS combination. In each scenario, the CMC of SDDS decreases with an increase in weight percentage of HEC. The aggregation number (Nagg) of SDDS micelles is also found to decrease with an increase in weight percentage of HEC in the medium. The hydrodynamic diameter (Dh) and zeta potential (ζ) of the polymer-surfactant aggregate, these two parameters have been found to be strongly dependent on the amphiphile concentration. Finally, investigations of the surface morphologies by taking Field Emission Scanning Electron Microscopy (FESEM), high resolution transmission electron microscopy (HR-TEM) and fluorescence microscopy techniques assist the experimental data.

Excited State Dynamics of Dibenzothiophene Derivatives.

Polycyclic aromatic sulfur heterocycles are environmental pollutants formed from incomplete combustion processes and crude oil spills. Their excited state dynamics are not understood. Herein, femtosecond transient absorption is combined with steady-state spectroscopy and computational methods to elucidate the relaxation mechanisms of three dibenzothiophene derivatives. The low-energy singlet and triplet states all have ππ* character in the Franck-Condon region, and two minima were located in the S1 surface. Excitation at 320 nm populates their S1 state directly, which relaxes with lifetimes ranging from 4 to 13 ps. Most of the S1 population undergoes efficient intersystem crossing to the triplet state with lifetimes ranging from 820 ± 50 to 900 ± 30 ps. The compounds exhibit negligible nonradiative internal conversion, low fluorescence yields of 1.2 to 1.6%, and triplet yields of ca. 98%. Linear interpolation of internal coordinates reveals the chemical basis for relaxing the spin-forbidden intersystem crossing in these π-aromatic systems.

Size-dependent solvatochromism of CdS nanoparticles: Experimental absorption and fluorescence analyses

Owing to the quantum confinement effect, a nanocrystal shows a unique blend of molecular and solid properties: discrete energy levels with large polarizabilities which could respond to solvent environments. In this paper, we used steady-state fluorescence and absorption spectroscopy to study the size-dependent solvatochromism of CdS nanoparticles. The dipolar character of the ground state and the first excited state of the nanoparticle were also investigated with in the framework of Onsager reaction field theory using Ooshika–Mataga–Lippert equation. The results of the present study revealed that the solvatochromic responses were size dependent. Additionally, the responses increased with the particle size up to a certain size beyond which the response started to fall again. Hence, fine-tuning the nanoparticle's solvatochromic response and band gap is possible by appropriate choice of size. Moreover, size-dependent dipole moment values of CdS nanoparticles were determined. Based on the findings of the present study it was noted that steady-state fluorescence and absorption spectroscopy methods can efficiently be used to study the size-dependent solvatochromism of CdS nanoparticles.

Study on Creep Characteristics and Long-Term Strength of Mud-Calcareous Conglomerates in the Three Gorges Reservoir Area

The study of the time-dependent properties of engineering rock masses is a frontier topic in rock mechanics. In this study, creep tests and stress relaxation tests were conducted on mud-calcareous conglomerates from the Three Gorges Reservoir Area, and the long-term strength values of the conglomerate specimens were determined via different methods based on the test curves. By comparing these mainstream long-term strength determination methods, it was found that each of these methods have their own drawbacks. For example, the transition creep method requires a high accuracy of the test curve and only obtains an approximate strength interval rather than an accurate value. The long-term strength values determined by the isochronous stress–strain curve method are strongly influenced by subjective factors, among other things. Therefore, this paper proposes a new method for determining long-term strength, called the steady-state creep rate method, based on stress intervals. By comparison, the long-term strength values determined via this method are in good agreement with the transition creep method, the volume expansion method, and the stress relaxation method.

Optimal EV scheduling and voltage security via an online bi-layer steady-state assessment method considering uncertainties

Steady-state voltage security region (SVSR) is an important criterion that can intuitively and effectively evaluate the power system's operation security and overall safety margin. However, there is no literature on its application to electric vehicle (EV) proliferation. Since EV introduces dynamism and uncertainties to the grid, most existing indices cannot assess the grid accurately. Given this, we propose a load margin index (LMI) based on SVSR considering uncertainties. This is used to assess the impact of EV proliferation via a bi-layer optimal EV scheduling model. The upper layer of the model solves a dispatching plan for EV aggregators (EVA) by maximizing the LMI and minimizing the deviation between the upper and lower layer power schedules. The lower layer models each EV's charging/discharging strategy by minimizing the EV's operating cost, the EV user's target residual energy, and the deviation between the lower and upper layer schedules. We also employ a real-time scheduling plan to further adjust the day-ahead scheduling due to forecast errors. A case study based on the IEEE-33 node distribution network verifies the practicability and effectiveness of the proposed method.

Assessment of Critical Loads of Nitrogen Deposition in Natural Ecosystems of China

Excessive nitrogen (N) deposition causes a series of environmental problems, including biodiversity loss. Therefore, assessing current N deposition thresholds of natural ecosystems is critical for regional N management and pollution control. In this study, the critical loads of N deposition in mainland China were estimated using the steady-state mass balance method, and the spatial distribution of ecosystems that exceeded the critical load was evaluated. The results showed that areas with critical loads of N deposition higher than 56, in the range of 14-56, and lower than 14 kg·(hm2·a)-1 accounted for 6%, 67%, and 27% of that in China, respectively. The areas with higher critical loads of N deposition were mainly distributed in the eastern Tibetan Plateau, northeastern Inner Mongolia, and parts of south China. Lower critical loads of N deposition were mainly distributed in the western Tibetan Plateau, northwest China, and parts of southeast China. Moreover, the areas where N deposition exceeded the critical loads accounted for 21% of that in mainland China, being mainly distributed in southeast and northeast China. The exceedances of critical loads of N deposition in northeast China, northwest China, and the Qinghai-Tibet Plateau were generally lower than 14 kg·(hm2·a)-1. Therefore, the management and control of N in these areas that exceeded the critical load of deposition is more worthy of future attention.

Solubility and diffusivity of CO2 and C2H4 in the ionic liquids 1-alkyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)imide by tube-in-tube reactor method

In this paper, the solubility and diffusivity of CO2/C2H4 in ionic liquids 1-Ethyl-2,3-dimethylimidazolium Bis(trifluoromethanesulfonyl)imide([Emmim][Tf2N]), 1-Propyl-2,3-dimethylimidazolium Bis(trifluoromethanesulfonyl)imide([Pmmim][Tf2N]), 1-Butyl-2,3-dimethylimidazolium Bis(trifluoromethanesulfonyl)imide([Bmmim][Tf2N]) and 1-Hexyl-2,3-dimethylimidazolium Bis(trifluoromethanesulfonyl)imide([Hmmim][Tf2N])) are measured at the temperature range of 303–333 K with a tube-in-tube reactor. The new device can greatly decrease the measurement time to several minutes in the tube-in-tube reactor. The solubility data is determined by the steady-state method with less than 10% deviation compared with previous reports. The diffusivity data is measured by an unsteady-state method within 3 min. The diffusion coefficient of CO2 in ionic liquids can be predicted with Morgan’s diffusivity correlation equation. For the diffusivity of C2H4 in ionic liquids, an empirical formula is developed and the predicted values using this correlation agree well with measured values with less than 17% deviation. The measured solubility and diffusivity data of CO2/C2H4 in ionic liquids and corresponding correlations can help to develop a more efficient process involving CO2/C2H4/ionic liquids system.

A numerical solution on pore diffusion equation with a volume of limited bath boundary condition using the finite difference method

Abstract Numerical approaches have long been used to examine material behaviors that are governed by diffusion. The surface water and groundwater become polluted with regard to time. The pollutants travel from place to place in extended time intervals interacting with the solid soil particles. The diffusion of solute with solid soil particles idealized as spheres are studied in this dissertation. The objective was to numerically simulate diffusion through a sphere. A steady-state finite difference method was used to study the diffusion in a sphere. It was assumed that a bulk liquid solution interacts with solid spheres through a diffusion limited process which is equivalent to a volume of limited bath boundary condition. A sphere of radius 0.07 cm is placed in the beaker containing the solution. The radius of the sphere is divided into 15 nodes each of radius 0.005 cm. Initially, the sphere is free from the solute. As time progresses the diffusion in the sphere takes place. The solute from outside the sphere gets infused in the sphere. By using a numerical technique, the concentration at different nodes at different time intervals is studied. The process is carried out for two different solutions with different concentration values.

Unveiling the Intimate Mechanism of the Crocin Antioxidant Properties by Radiolytic Analysis and Molecular Simulations.

The successive steps of the oxidation mechanism of crocin, a major compound of saffron, by the free OH• radical are investigated by pulse radiolysis, steady-state (gamma) radiolysis methods, and molecular simulations. The optical absorption properties of the transient species and their reaction rate constants are determined. The absorption spectrum of the oxidized radical of crocin resulting from the H-abstraction presents a maximum of 678 nm and a band of 441 nm, almost as intense as that of crocin. The spectrum of the covalent dimer of this radical contains an intense band at 441 nm and a weaker band at 330 nm. The final oxidized crocin, issued from radical disproportionation, absorbs weaker with a maximum of 330 nm. The molecular simulation results suggest that the OH• radical is electrostatically attracted by the terminal sugar and is scavenged predominantly by the neighbor methyl site of the polyene chain as in a sugar-driven mechanism. Based on detailed experimental and theoretical investigations, the antioxidant properties of crocin are highlighted.

Active Fault Isolation for Multimode Fault Systems Based on a Set Separation Indicator.

This paper considers the active fault isolation problem for a class of uncertain multimode fault systems with a high-dimensional state-space model. It has been observed that the existing approaches in the literature based on a steady-state active fault isolation method are often accompanied by a large delay in making the correct isolation decision. To reduce such fault isolation latency significantly, this paper proposes a fast online active fault isolation method based on the construction of residual transient-state reachable set and transient-state separating hyperplane. The novelty and benefit of this strategy lies in the embedding of a new component called the set separation indicator, which is designed offline to distinguish the residual transient-state reachable sets of different system configurations at any given moment. Based on the results delivered by the set separation indicator, one can determine the specific moments at which the deterministic isolation is to be implemented during online diagnostics. Meanwhile, some alternative constant inputs can also be evaluated for isolation effects to determine better auxiliary excitation signals with smaller amplitudes and more differentiated separating hyperplanes. The validity of these results is verified by both a numerical comparison and an FPGA-in-loop experiment.

Laisk measurements in the nonsteady state: Tests in plants exposed to warming and variable CO2 concentrations.

Light respiration (RL) is an important component of plant carbon balance and a key parameter in photosynthesis models. RL is often measured using the Laisk method, a gas exchange technique that is traditionally employed under steady-state conditions. However, a nonsteady-state dynamic assimilation technique (DAT) may allow for more rapid Laisk measurements. In 2 studies, we examined the efficacy of DAT for estimating RL and the parameter Ci* (the intercellular CO2 concentration where Rubisco's oxygenation velocity is twice its carboxylation velocity), which is also derived from the Laisk technique. In the first study, we compared DAT and steady-state RL and Ci* estimates in paper birch (Betula papyrifera) growing under control and elevated temperature and CO2 concentrations. In the second, we compared DAT-estimated RL and Ci* in hybrid poplar (Populus nigra L. × P. maximowiczii A. Henry "NM6") exposed to high or low CO2 concentration pre-treatments. The DAT and steady-state methods provided similar RL estimates in B. papyrifera, and we found little acclimation of RL to temperature or CO2; however, Ci* was higher when measured with DAT compared to steady-state methods. These Ci* differences were amplified by the high or low CO2 pre-treatments. We propose that changes in the export of glycine from photorespiration may explain these apparent differences in Ci*.

Pre-Steady-State Kinetic Characterization of an Antibiotic-Resistant Mutant of Staphylococcus aureus DNA Polymerase PolC.

The emergence and spread of antibiotic resistance in bacterial pathogens are serious and ongoing threats to public health. Since chromosome replication is essential to cell growth and pathogenesis, the essential DNA polymerases in bacteria have long been targets of antimicrobial development, although none have yet advanced to the market. Here, we use transient-state kinetic methods to characterize the inhibition of the PolC replicative DNA polymerase from Staphylococcus aureus by 2-methoxyethyl-6-(3'-ethyl-4'-methylanilino)uracil (ME-EMAU), a member of the 6-anilinouracil compounds that specifically target PolC enzymes, which are found in low-GC content Gram-positive bacteria. We find that ME-EMAU binds to S. aureus PolC with a dissociation constant of 14 nM, more than 200-fold tighter than the previously reported inhibition constant, which was determined using steady-state kinetic methods. This tight binding is driven by a very slow off rate of 0.006 s-1. We also characterized the kinetics of nucleotide incorporation by PolC containing a mutation of phenylalanine 1261 to leucine (F1261L). The F1261L mutation decreases ME-EMAU binding affinity by at least 3,500-fold but also decreases the maximal rate of nucleotide incorporation by 11.5-fold. This suggests that bacteria acquiring this mutation would be likely to replicate slowly and be unable to out-compete wild-type strains in the absence of inhibitors, reducing the likelihood of the resistant bacteria propagating and spreading resistance.

Research on thermal contact resistance between C/C and resin thermal protection materials for solid rocket motor nozzles considering real surface roughness

C/C composite and resin materials have been applied in rocket motor nozzles. This study aims to investigate the thermal contact resistance (TCR) between C/C composite and resin materials. Contact surfaces are scanned by surface morphological-measuring instrument. The TCR values are solved numerically. With the steady-state heat flux method, the TCR values are experimentally measured at different temperatures and pressures. The study results show that the TCR value between C/C composite and resin materials varies in the range of 1.8245 × 10–3 ∼7.5851 × 10–3 K·m2·W-1 at different pressures and temperatures. The average TCR error between numerical analysis and test results is 8%, which indicates a high accuracy. The developed TCR numerical prediction model can provide a reference for thermal-structural design and analysis of nozzles.

Repeated falling-head method for in situ measurements of saturated hydraulic conductivity using a single cylinder

A simple, repeated falling-head (RFH) method, which uses an inexpensive portable cylinder to quickly determine field-saturated hydraulic conductivity (Kfs), is presented. A cylinder of radius r, inserted vertically from the soil surface to a depth d, is used as a water supply tank, through which water infiltrates into the soil. The falling-head test is repeated without allowing the cylinder to be drained entirely to eliminate the effects of the initial soil moisture conditions. Either change in the water level (H) in the water supply cylinder or strong linearity between the infiltration flux (qs) and H can be used to determine Kfs directly or by multiplying the slope with an empirical ring-installation scaling length, Lg; thus, no soil-dependent variable is necessary. To obtain the Lg value for various conditions, we carried out numerical experiments using HYDRUS (2D/3D) with a recently implemented reservoir boundary condition for six different soil textures, ranging from coarse soil (e.g., sand) to fine soil (e.g., silty clay loam), and two different ranges of water levels, 15 ≤ H ≤ 25 cm and 2 ≤ H ≤ 6 cm. Numerical results showed that the Lg has a strong linear dependence on d and r, where Lg increases as d and r increase. We propose a new linear model to determine Lg with optimized coefficients for each H range. Numerical results showed no significant differences in the estimated Kfs after the second repetition, confirming that repeating the falling head test twice is sufficient. The newly obtained Lg values were then applied to the experimental data obtained at multiple fields having different soil textures. The Kfs values determined using the RFH method agreed well with those measured using the field two-ponding depths steady-state method and/or the FH method in the lab. These results demonstrate the reliability of the proposed RFH method.

Experimental and computational assessment into the heat transfer for the blade multicavity tips

In the gas turbine, the tip region of the shroudless blade is under severe heat load, and thus is seriously ablated. Therefore, an in-depth understanding of the tip heat transfer distributions is of great significance for tip cooling design. In the present work, the heat transfer coefficient distributions of the multicavity tips were measured by a steady-state thermal-analysis method with Infrared camera. The measurements were conducted under two inlet Reynolds number conditions (1.10 × 105, 2.23 × 105) and two tip gaps (1.6 %, 3.5 % Chord length). In addition, the computational simulations verified by the experimental data were conducted to attain the detailed flow field near the tip, and to gain insight into the heat transfer characteristics. Measured results show that additional hot spots are detected behind the rib for the multicavity tips with three or four cavities owing to the leakage flow reattachment. The heat transfer at the suction-side corner is also enhanced by the multicavity tips, whereas a low heat transfer coefficient region is found in the corner in front of the rib. Increasing the inlet Reynolds number would not change the heat transfer patterns, but would evidently increase the heat transfer coefficient values. Adopting a larger tip gap also increases the heat transfer coefficient values, but the effect is not so obviously as the inlet Reynolds number. Compared with the conventional one-cavity tip, the multicavity tips can reduce the aerodynamic losses, and the loss values are reduced by about 2 %.

Controllable preparation of high-quality MAPbCl3 perovskite single crystal sheets

Hybrid perovskite CH3NH3PbCl3 single crystals have received much attention in the field of photodetectors due to their outstanding optoelectronic properties. Herein, a simple growth method of CH3NH3PbCl3 single crystal sheets was demonstrated in detail. The steady-state solution micro-reaction method with the small-hole rate control and the liquid-surface height control effectively solves the disadvantages of liquid- and gas-phase methods and realizes the preparation of a CH3NH3PbCl3 single crystal sheet with the controllable growth rate, size, and thickness, and good crystal quality and high crystallinity. Moreover, photodetectors based on one CH3NH3PbCl3 single crystal perovskite were fabricated with the responsivity of 80 mA/W under 395 nm light at 5 V. Meanwhile, a rise time of 22.3 µs and a fall time of 16.5 µs were obtained, indicative of a relatively fast response. These findings demonstrate that the CH3NH3PbCl3 single crystal perovskite have great potential applications in optoelectronic fields.

A novel method for simultaneous determination of relative permeability and capillary pressure from corefloods (gas/CO2–water systems)

Enhanced oil recovery (EOR) using CO2 injection is being investigated as a feasible technique for oil reservoirs. The ability of a reservoir to store CO2 for a long time presents an opportunity to create sustainable solutions to the problems posed by the continued use of fossil fuels and climate change, and to support the commitment to regional, national, and global agreements to reduce CO2 emissions. Injection strategies such as water-alternate-gas (WAG) or carbonised water injection (CWI) have been proposed to overcome the issue of low sweep efficiency of CO2 flood in the reservoir. An understanding of the relative permeability and capillary pressure behaviour is necessary to simulate these processes in porous media. The steady-state coreflood test is a widely accepted industrial method to determine relative permeability (Kr), but the capillary pressure (Pc) must be found from other sources (porous plate, mercury injection, and centrifuge tests). A significant difference between the capillary pressure determined from corefloods and by other methods is widely presented in the literature. This work presents a novel coreflood method for the simultaneous determination of relative permeability (Kr) and capillary pressure (Pc). The main idea is to use the stabilised data of the steady-state method along with the transient data of the pressure drop. Therefore, in the proposed steady-state-transient test (SSTT), the transient pressure drop data across the core, between the sequential steady-states, are used instead of the traditionally utilised Pc-curve.