Assessment Of Long-term Stability Research Articles

Statistical Analysis for Quality Control of Monodispersed Polystyrene Particles Certified Reference Materials

Monodispersed polystyrene latex (PSL) particles serve as certified reference materials (CRMs) for ensuring quality, method validation, and calibration of particle size measuring instruments. They were produced in compliance with ISO 17034:2016 standards. However, limitations arise in the quality control of CRM characteristics due to challenges in synthesizing particles of consistent size across multiple batches. It is widely recognized that variations in particle size homogeneity between batches can occur in the particle manufacturing process even when conducted under identical conditions and ingredients. This paper aims to explain and demonstrate statistical analyses conforming to ISO Guide 35:2017 used for quality control and certifying reference values for monodispersed polystyrene particles. The procedure can be divided into three steps: 1) preliminary check by using dynamic light scattering (DLS), 2) preliminary check by using transmission electron microscopy (TEM), and 3) final homogeneity testing, along with short-term and long-term stability assessment and characterization. The described protocol can control the quality of particles from multiple batch productions by establishing criteria at each step to ensure particle size consistency. The certified value of a 100 nm diameter monodispersed polystyrene particle produced by the National Institute of Metrology, Thailand (NIMT) is 105.5 ± 4.6 nm, acceptable for measurement traceability for testing and calibration services. Keywords: Quality control, polystyrene particles, certified reference materials

Physicochemical Characteristics and Stability Assessment of A Topical Formulation Comprising Allium cepa and Quercetin for Cutaneous Scar Management

The 12% Allium cepa extract topical formulation, with proven clinical benefits, targets improved surgical scar appearance. This study aims to comprehensively assess the physicochemical characteristics and stability of a scar-reducing formulation (15% Allium cepa-micellar extract, 0.01% quercetin). In vitro-release and skin permeation studies were conducted, alongside FTIR and DSC analyses to elucidate the skin permeation mechanism. Quercetin remaining at 25 and 40 °C ranged from 99 to 100% (day 60) and 101 to 104% (day 90), while antioxidant activity (53-65%, day 90) remained comparable to the standard quercetin (84.70% at 40 μg/mL). In the context of in vitro quercetin release, the performances were ranked as shallot-micellar extract > scar-reducing formulation plus shallot-micellar extract > scar-reducing formulation, with no significant differences observed (P < 0.05). Importantly, scar-reducing formulation plus shallot-micellar extract and shallot-micellar extract showed a significant difference (P < 0.05) compared to shallot-water extract and the commercial product. The treated skin showed minor changes in the microstructure compared to untreated skin, indicating a gentle formulation, as observed in the FT-IR spectra and DSC thermograms. The findings from skin permeation mechanism studies imply that the scar-reducing formulation may deposit on the skin surface with minor alterations to the skin microstructure. A crucial consideration for future investigations is a long-term stability assessment of at least 12 months at 30°C, following ASEAN guidelines. The scar-reducing formulation was stable at 25°C, without exceeding 40°C for 90 days. Storage at 4°C is not recommended due to the potential risk of decreased solubility and quercetin precipitation.

Investigating the impact of various etching agents on Ti3C2Tx MXene synthesis for electrochemical energy conversion

MXenes represent a revolutionary class of two-dimensional (2D) materials that have garnered significant attention due to their unique properties, including excellent electrical conductivity, and remarkable mechanical strength. This study investigates the influence of different etching agents on the synthesis of MXenes for electrochemical energy conversion applications, particularly in methanol oxidation reactions (MOR). Morphological characterization, particle distribution and sizing, elemental analysis, and surface chemistry assessments were conducted using field emission scanning electron microscopy (FESEM), elemental mapping, transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). Electrochemical techniques such as cyclic voltammetry (CV), electrochemical active surface area (ECSA), Tafel analysis, electrochemical impedance spectroscopy (EIS), and long-term stability assessment were employed. The study reveals that PtRu/MXene synthesized with the FeF3/HCl etching route exhibits the highest ECSA value and peak current density, being 12.3 times and 3.63 times higher than those achieved via the LiF/HCl etching route. The kinetic rate, tolerance to catalyst poisoning and long-term stability also show the better results for this etching route. These findings suggest promising potential for PtRu/MXene_FeF3/HCl as an effective anodic electrocatalyst in direct methanol fuel cell (DMFC) applications.

Enhanced Rock Slope Stability Analysis: Integrating the Partial Factor Method into the Limit Equilibrium Method

Rock slope stability is crucial for sustainable design. Especially concerning natural or artificial rock-cut slopes. The stability of these slopes depends largely on features of rock mass, particularly discontinuities. Failure modes are determined by these features and are evaluated using kinematics analysis with stereographic projections. Various methods exist for analyzing rock slopes, including the limit equilibrium method (LEM), which assesses stability based on a factor of safety (FS). Conversely, the partial factor method (PFM), predominantly used in Europe, offers a more reliable and probabilistic approach, incorporating uncertainty factors. Although Eurocode, which employs the PFM, is widely utilized, it faces disputes and undergoes updates based on ISRM recommendations. The partial factor method is considered more conservative than the limit equilibrium method due to its comprehensive probabilistic approach. The choice between methods depends on project requirements, data availability, and expertise. This study compares the limit equilibrium and partial factor methods for rock slope analysis, concluding that the partial factor method is more conservative and sustainable for long-term stability assessment. Whereas, the traditional method is often used for short-term assessments.

Assessment of Long-Term Stability of External Quality Control Materials: Defibrinated Pooled Plasma for Examination of Hepatitis Viral Markers

Assessment of Long-Term Stability of External Quality Control Materials: Defibrinated Pooled Plasma for Examination of Hepatitis Viral Markers

Green Additives in Chitosan-based Bioplastic Films: Long-term Stability Assessment and Aging Effects.

Although biomass-based alternatives for the manufacturing of bioplastic films are an important aspect of a more sustainable future, their physicochemical properties need to be able to compete with the existing market to establish them as a viable alternative. One important factor that is often neglected is the long-term stability of renewables-based functional materials, as they should neither degrade after a day or week, nor last forever. One material showing high potential in this regard, also due to its intrinsic biodegradability and antibacterial properties, is chitosan, which can form stable, self-standing films. We previously showed that green additives introduce a broad tunability of the chitosan-based material properties. In this work, we investigate the long-term stability and related degradation processes of chitosan-based bioplastics by assessing their physicochemical properties over 400 days. It was found that the film properties change similarly for samples stored in the fridge (4 °C, dark) as at ambient conditions (20 °C, light/dark cycles of the day). Additives with high vapor pressure, such as glycerol, evaporate and degrade, causing both brittleness and discoloration. In contrast, films with the addition of crosslinking additives, such as citric acid, show high stability also over a long time, bearing great preconditions for practical applications. This knowledge serves as a stepping-stone to utilizing chitosan as an alternative material for renewable-resourced bioplastic products.

Accurate color characterization of solar photovoltaic modules for building integration

Accurate and reproducible color characterization is essential for colored building integrated photovoltaic products, both for manufacturing quality control and assessing long-term color stability. However, existing characterization techniques struggle to accurately determine color when a surface is behind a transparent layer like a solar PV laminate. In this study, we compare different colorimetric techniques and propose an innovative colorimeter based on a fiber optic spectrometer and large area illumination to address this issue. Samples with varying transparent glass thicknesses and underlying colors are laminated and characterized using a scanner, an integrated sphere spectrometer, a commercial portable colorimeter, and the proposed large area illumination colorimeter. Results show that common scanners produce darker images and inaccurate color determination due to light losses in the glass. As glass thickness increases, reflectance decreases with the integrated sphere spectrometer and portable colorimeter. However, the large area illumination colorimeter exhibits only minimal signal reduction. High reflective foils experience more reflectance reduction with thicker glass than low reflective ones. All devices yield comparable results without the glass layer. The large area illumination colorimeter, compensating for light losses, proves to be a suitable solution for accurately measuring color under glass laminates using reflected light. For example, it reduces the color change from 57 (commercial portable colorimeter) to only 3 for an ivory colored glass laminate. This innovative tool has the potential to improve color characterization in building integrated photovoltaic products, enabling better manufacturing quality control and assessment of long-term color stability.

Forty-year investigation of wave power in energetic region of Persian Gulf in Iranian territorial waters by using short-term and new long-term stability assessment parameters

Forty-year investigation of wave power in energetic region of Persian Gulf in Iranian territorial waters by using short-term and new long-term stability assessment parameters

Accelerated in vitro oxidative degradation testing of polypropylene surgical mesh.

Polypropylene (PP) surgical mesh had reasonable success in repair of hernia and treatment of stress urinary incontinence (SUI); however, their use for the repair of pelvic organ prolapse (POP) resulted in highly variable results with lifelong complications in some patients. One of several factors that could be associated with mesh-related POP complications is changes in the properties of the implanted surgical mesh due to oxidative degradation of PP in vivo. Currently, there are no standardized in vitro bench testing methods available for assessing the susceptibility to oxidative degradation and estimating long-term in vivo stability of surgical mesh. In this work, we adapted a previously reported automated reactive accelerated aging (aRAA) system, which uses elevated temperatures and high concentrations of hydrogen peroxide (H2 O2 ), for accelerated bench-top oxidative degradation testing of PP surgical mesh. Since H2 O2 is highly unstable at elevated temperatures and for prolonged periods, the aRAA system involves a feedback loop based on electrochemical detection methods to maintain consistent H2 O2 concentration in test solutions. Four PP mesh samples with varying mesh knit designs, filament diameter, weight, and % porosity, were selected for testing using aRAA up to 4 weeks and characterized using thermal analysis, Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and scanning electron microscopy (SEM). Additionally, the oxidation index (OI) values were calculated based on the FTIR-ATR spectra to estimate the oxidative degradation and oxidation reaction kinetics of PP surgical mesh. The OI values and surface damage in the form of surface flaking, peeling, and formation of transverse cracks increased with aRAA aging time. The aRAA test method introduced here could be used to standardize the assessment of long-term stability of surgical mesh and may also be adopted for accelerated oxidative degradation testing of other polymer-based medical devices.

Damage Evolution and Failure Mechanism of Red-Bed Rock under Drying–Wetting Cycles

The rock mass on the bank slope of the Three Gorges Reservoir (TGR) area often suffers from a drying–wetting cycle (DWC). How the DWCs significantly affect the mechanical properties and the stability of the rock mass is worth comprehensively investigating. In this study, the influence of the DWC on the mechanical properties of red-bed rock, mainly purplish red argillaceous siltstone, is explored in detail. Triaxial compression tests were conducted on siltstones that were initially subjected to different DWCs. The results show that DWCs lead to a decrease in mechanical properties such as peak stress, residual stress, and elastic modulus, while an increase in confining pressure (CP) levels leads to an increase in these mechanical properties. Significant correlations are found between the energy parameters and the DWC or the CP. Notably, the total absorption energy (TAE) demonstrates a positive correlation with the CP, but the capability of siltstones to absorb energy shows a negative correlation with DWC. Moreover, the study also examines the damage evolution laws of rocks under different DWCs by proposing a damage variable (DV). Results demonstrate that the effect of the CP on the DV is more pronounced than that of DWCs. A novel brittleness index (BI) was also proposed for estimating rock brittleness through damage strain rate analysis. The effectiveness of the proposed BI is validated by evaluating the effects of DWCs and CP on rock brittleness. Finally, the failure mechanism of the rocks under water–rock interaction is revealed. The weakening of mechanical properties occurs due to the formation of microcracks in response to DWCs. These findings provide valuable guidance for the long-term stability assessment of bank slope engineering projects under DWCs.

Study on Nonlinear Viscoelastic Constitutive Equations for Rock

Numerical simulation is one of the effective tools for the long-term stability assessment of underground structures. The reliability improvement of the numerical simulation requires precise constitutive equations to reproduce time-dependent behavior of rock such as loading-rate dependence, creep, and relaxation. These time-dependent behaviors of rock have nonlinearity between stress and strain rate and are influenced by surrounding environment. A number of constitutive equations have been proposed in previous studies; however, the equations based on the theory of linear viscoelasticity have difficulty reproducing accurately the time-dependent behavior of rock, and most of the equations based on the theory of viscoplasticity have been applied to the limited loading condition such as creep. In this article, nonlinear viscoelastic constitutive equations for rock proposed by the authors were introduced, and their exact solutions and application to experimental results were summarized. These equations can reproduce nonlinear time-dependent behavior and not only brittle but also ductile failures of rock and can be applied to the behavior under various loading conditions and experiment environment. In the equations, compliance or inelastic strain is assumed to be increased with time, but the functions and their combinations are of great variety. Hence, the differences of the solutions and applicability of the equations were detailed, and in addition future subjects were presented.

Prospect and Challenges of Hydrate-Based Hydrogen Storage in the Low-Carbon Future

Hydrogen hydrate is a promising material for safe and potentially cost-effective hydrogen storage. In particular, hydrogen hydrate has potential for applications in large-scale stationary energy storage to dampen the temporal variation of renewable energy, for example, in the form of hydrogen-ready gas-fired power plants for generating energy when the renewable power is not available. Preliminary SWOT (strengths, weaknesses, opportunities, threats) analysis indicates that such hydrate-based hydrogen storage (HBHS) has intrinsic competitive edges. However, while the theoretical hydrogen density of the hydrate could reach ∼5 wt %, experiments have not achieved such a high hydrogen storage capacity under practical conditions. This low gravimetric hydrogen density, plus the slow kinetics of hydrogen inclusion in the hydrate, presents an outstanding challenge for commercializing the HBHS. Future research is urged to resolve both the gaps in knowledge and technological barriers for realizing this unconventional technology. Particular future directions include the elucidation of the working mechanism of hydrate promoters, rational designs of new promoters, upscaled experiments and demonstrations, the assessment of long-term stability of hydrogen hydrates, and systematic SWOT analysis. This paper offers an insightful view of the HBHS in low-emission economies.

Assessment of Long-Term Stability of Encapsulated Agricultural Biologicals in Lipid-Coated Alginate Beads

Assessment of Long-Term Stability of Encapsulated Agricultural Biologicals in Lipid-Coated Alginate Beads

Long-term mechanical analysis of tunnel structures in rheological rock considering the degradation of primary lining

Rock load on lining structures increases over time for tunnels buried in rheological rock, and in addition deterioration of primary lining is common due to its structural characteristics and service environment attack, where these delayed features affect the mechanical response of tunnels. However, accounting for these delayed features in long-term stability assessment of tunnel structures is complex and has not attracted enough attention. In this paper, an analytical approach is proposed for investigating long-term mechanical response of tunnel structures in rheological rock influenced by degradation of primary lining. For this purpose, degradation of primary lining, characterized by decreasing concrete stiffness over time, is quantitatively described by an exponential model. The rheological characteristic of surrounding rock is simulated by the Burgers model. The time-varying solutions for rock deformation and support pressure are obtained by considering the coordinated interaction between surrounding rock and linings, and their correctness is verified by comparing them with numerical results. The results revealed that the pressure imposed on linings due to the rheological behavior of surrounding rock increases over time. As the primary lining degrades, the rheological load is transferred from primary lining to secondary lining, leading to increasing pressure on secondary lining; and a faster degradation rate of primary lining leads to greater pressure on secondary lining. Therefore, the primary lining should not be overlooked in long-term safety assessment of operation tunnels because of its role in bearing and transmitting load. Finally, the tunnel's design and operational maintenance strategy are discussed when the delay effects of surrounding rock and lining are taken into account.

Stability analysis of Pingdingshan pear-shaped multi-mudstone interbedded salt cavern gas storage

In China, salt cavern gas storages are typically constructed in strata of complicated bedded salt rock, which are made up of numerous thin interlayers and salt rock that contains impurity. The long-term stability and safety assessment of underground caverns is crucial for the safe operation of gas storage in this type of complicated strata. In order to more accurately describe the long-term creep characteristics of salt rock and mudstone, the fractional derivative creep-damage (FDCD) constitutive model is used in this work. Earlier researches have also demonstrated the advantages of this model when it comes to long-term creep. Pingdingshan (PDS)'s shape and dimensions are developed in accordance with the formation conditions, and a three-dimensional geological model is built according to the designed gas storage. The long-term stability and safety of gas storage under various constant operating internal gas pressures (IGP), cyclic IGP, and gas extraction rates are investigated based on the comprehensive evaluation criteria including deformation, volume shrinkage rate, safety factor, and plastic zone. The results reveal that when the constant operating IGP is 13 MPa, and the cyclic IGP is 13–27 MPa PDS gas storage has good long-term stability and safety. While the plastic zone of mudstone interlayer is still presented at the top and bottom of the gas storage at IGP = 13–27 MPa, and the plastic zone is more pronounced at low constant and cyclic IGP levels. The safety factor of rock mass close to the sidewalls is always <1.5 throughout the long-term operation of gas storage, which makes it more vulnerable to dilatancy failure and requires attention. The deformation and volume shrinkage of gas storage are greatly impacted by the gas extraction rate, and the evolution characteristics of 4 indicators under various gas extraction rates are provided. This study provides a crucial reference for the design of gas storage in China's intricate salt rock regions with multiple interlayers in the PDS region.

Creep Fracture Characteristics and the Constitutive Model of Salt Rock under a Coupled Thermo-Mechanical Environment

The fracture extension characteristics of salt rocks under creep play an important role in the long-term safety and stability assessment of underground compressed air storage reservoirs. To study the fracture evolution characteristics of salt rock with time, the present study modified the Charles creep fracture intrinsic model and calibrated the A and n of the fracture extension coefficient parameters by creep fracture experiments with a constant stress rate loading method for salt rock under different temperature conditions. Finally, the modified Charles model was embedded into PFC (particle flow code) to simulate the fracture of salt rock numerically and the results were verified theoretically. The results show that (1) the fracture extension rate is related to the parameters A and n in addition to the stress intensity factor; (2) both n and A gradually decrease with the increase of temperature, and an decrease of n and A represents the decrease of fracture creep extension rate; and (3) the longer the initial fracture length of the specimen, the smaller the fracture time. The results of this study can provide theoretical guidance for evaluating the confinement of underground compressed air storage reservoirs.

Experimental Investigation on Long-Term Strength and Acoustic Emission Characteristics of Coal Pillar under Inclined Compression Loading

Pillar rheological failure is one of the important reasons to induce earthquake, surface collapse, and water inrush disaster in underground mining engineering. Pillar is generally present under an inclined state and is significantly influenced by combining compression and shear loading. However, many scholars regard the long-term strength of coal or rock mass under pure uniaxial compression loading as the main evolution index of pillar strength, which is not consistent with engineering practice. In this paper, a new inclined uniaxial compression strength (IUCS) test system was developed and then used to carry out the IUCS test and creep test of coal specimens combined with an acoustic emission (AE) technology at various inclination angles (0°, 5°, 10°, 15°, and 20°). The variation of time-dependent deformation, peak strength, long-term strength (LTS), creep fracture model, and AE behavior of the coal with the inclination angels were discussed in detail. The results indicated that the peak strength and LTS of the coal nonlinearly decreased with the inclination angle increasing. The proportion of the peak strength to the LTS had remained constant between 58.5% and 62.9%, which can be considered as the inherent properties of coal rock. The creep failure model of the coal was transformed from tension-splitting failure at the inclination angle of 0° and 5° to tension-shear failure at the inclination angle of 10°-20°, which revealed that the inclination angles were favorable to the initiation and propagation of shear cracks. No matter any inclination angles, AE events can be divided into quiet period, low amplitude rising period, and high amplitude rising period with the periodic mutation of multistage loading points. Moreover, the cumulative AE energy gradually decreases with the increase of the inclination angles, which indicated that the shear stress caused by the specimen inclination can make crack initiation and propagation with less energy absorption. The research results will assist in the long-term strength design and time-dependent stability assessment of the coal pillar.

Mechanical and micro-structural damage mechanisms of coal samples treated with dry–wet cycles

The construction of mine goafs as an underground reservoir to store and utilise mine water can effectively alleviate the contradiction between coal and water in the arid mining areas in western China. Understanding the effects of water on the mechanical properties and micro-structure of coal is essential for the stability design of coal pillar dams subjected to repeated water erosion. In this study, ultrasonic, X-ray diffraction, scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and uniaxial compression tests were conducted on coal samples with zero to five dry–wet cycles to investigate the changes in water absorption characteristics, pore structure, microscopic morphology, and mechanical properties as the number of dry–wet cycles, n, increased. Moreover, the connection of the pore structure and microscopic morphology with the mechanical damage was established. The results showed that the peak stress and elastic modulus were negative exponential functions of n. As n increased, the moisture content saturation and homogeneity of the coal sample increased, the number of pores increased, and tiny pores within the coal converted to medium-to-large pores. Further, the peak stress had a good negative linear fit to the porosity and internal damage defined by the integrated area of the T2 curve. According to the SEM test results, the coal underwent five stages during a dry–wet cycle: uniform and dense original structure, particle aggregation, pore development, fracture sprouting, and overall structural fragmentation, with a gradual decrease in structural integrity. The damage variable, D, was defined by the fractal dimension, F, of the SEM images, enabling the quantitative characterisation of the coal microscopic damage during the dry–wet cycle; moreover, D/F was an exponential function of n. Finally, the damage mechanism of coal samples was interpreted from both macroscopic (i.e. NMR) and microscopic (i.e. SEM) perspectives, and they showed good agreement. Our results could provide a reference for the long-term stability assessment and design of coal pillar dams.

Virtual surgical analysis: long-term cone beam computed tomography stability assessment of segmental bimaxillary surgery

The assessment of the stability of orthognathic surgery is often time-consuming, relies on manual re-identification of anatomical landmarks, and has been based on short-term follow-up. The purpose of this study was to propose and validate a semi-automated approach for three-dimensional (3D) assessment of the long-term stability of segmental bimaxillary surgery. The approach was developed and validated using cone beam computed tomography scans obtained at 2 weeks and 2 years postoperative. The stability of the surgical outcome was calculated as 3D translational and rotational differences between the short- and long-term postoperative positions of the individual bone segments. To evaluate reliability, intra-class correlation coefficients were calculated at a 95% confidence interval on measurements of two observers. Ten class II and III patients (six male, four female; mean age 24.4 years), who underwent a combined three-piece Le Fort I osteotomy, bilateral sagittal split osteotomy, and genioplasty, were included in the study. Intra- and inter-observer reliability were excellent (range 0.82–0.99). The range of the mean absolute difference of the intra- and inter-observer translational and rotational measurements were 0.14 mm (0.13)–0.44 mm (0.50) and 0.20° (0.16)–0.92° (0.78). The approach has excellent reliability for 3D assessment of long-term stability of segmental bimaxillary surgery.

Long-term Storage Stability Assessment of Omega-3-Fatty Acid Emulsified Formulation Containing Micronutrients

Long-term Storage Stability Assessment of Omega-3-Fatty Acid Emulsified Formulation Containing Micronutrients