True Conditions Research Articles

True triaxial unloading test on the mechanical behaviors of sandstone: Effects of the intermediate principal stress and structural plane

A series of true triaxial unloading tests are conducted on sandstone specimens with a single structural plane to investigate their mechanical behaviors and failure characteristics under different in situ stress states. The experimental results indicate that the dip angle of structural plane (θ) and the intermediate principal stress (σ2) have an important influence on the peak strength, cracking mode, and rockburst severity. The peak strength exhibits a first increase and then decrease as a function of σ2 for a constant θ. However, when σ2 is constant, the maximum peak strength is obtained at θ of 90°, and the minimum peak strength is obtained at θ of 30° or 45°. For the case of an inclined structural plane, the crack type at the tips of structural plane transforms from a mix of wing and anti-wing cracks to wing cracks with an increase in σ2, while the crack type around the tips of structural plane is always anti-wing cracks for the vertical structural plane, accompanied by a series of tensile cracks besides. The specimens with structural plane do not undergo slabbing failure regardless of θ, and always exhibit composite tensile-shear failure whatever the σ2 value is. With an increase in σ2 and θ, the intensity of the rockburst is consistent with the tendency of the peak strength. By analyzing the relationship between the cohesion (c), internal friction angle (φ), and θ in sandstone specimens, we incorporate θ into the true triaxial unloading strength criterion, and propose a modified linear Mogi-Coulomb criterion. Moreover, the crack propagation mechanism at the tips of structural plane, and closure degree of the structural plane under true triaxial unloading conditions are also discussed and summarized. This study provides theoretical guidance for stability assessment of surrounding rocks containing geological structures in deep complex stress environments.

Operando Spectroscopy to Understand Dynamic Structural Changes of Solid Catalysts.

Solid materials like heterogeneous catalysts are highly dynamic and continuously tend to change when exposed to the reaction environment. To understand the catalyst system under true reaction conditions,operando spectroscopy is the key to unravel small changes, which can ultimately lead to a significant difference in catalytic activity and selectivity. This was also the topic of the 7th International Congress on Operando Spectroscopy in Switzerland in 2023. In this article, we discuss various examples to introduce and demonstrate the importance of this area, including examples from emission control for clean air (e.g. CO oxidation), oxidation catalysis in the chemical industry (e.g. oxidation of isobutene), future power-to-X processes (electrocatalysis, CO2 hydrogenation to methanol), and non-oxidative conversion of methane. All of these processes are equally relevant to the chemical industry. Complementary operando techniques such as X-ray absorption spectroscopy (XAS), X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and Raman spectroscopy were utilized to derive the ultimate structure of the catalyst. The variety of conditions requires distinctly different operando cells that can reach a temperature range of 400-1000 °C and pressures up to 40 bar. The best compromise for both the spectroscopy and the catalytic reaction is needed. As an outlook, we highlight emerging methods such as modulation-excitation spectroscopy (MES) or quick-extended X-ray absorption fine structure (QEXAFS) and X-ray photon in/out techniques, which can provide better sensitivity or extend X-ray based operando studies.

DSC Derived (Ea & ΔG) Energetics and Aggregation Predictions for mAbs

The Arrhenius energy of activation of unfolding Ea unfolding and Gibbs free energy of unfolding ΔG unfolding have been calculated utilizing DSC differential scanning calorimetry for 4 mAbs (1 biosimilar) in 3 formulations. DSC derived ΔTm melting temperature changes for each mAb domain (CH2, Fab, CH3) at calorimetric scan rates at 60 °C, 90 °C, 150 °C and 200 °C / hr. were utilized to calculate the kinetic Eaunfolding. The DSC derived Ea trend with observed aggregate formation and can be used to predict%HMW formation post 9-month storage at 5 °C and 40 °C for all formulations analyzed. Additionally, thermodynamic ΔG unfolding energies were also derived (Tm, ΔCp and ΔH measurements) for each mAb at every scan rate to observe scan rate dependence of ΔG and for extrapolation to 0 °C/hr. (to report ΔG at true equilibrium conditions). Both derived thermodynamic ΔG and kinetic Ea energies were combined to build full energetic landscapes for mAb unfolding and aggregation. Statistical multivariate analysis of kinetic (Ea CH2, Ea Fab, Ea CH3) energies, thermodynamic (ΔG5 °C and ΔG40 °C) energies and in-silico modeled surface properties was also performed. Analysis revealed key significant parameters contributing to aggregation. These parameters were utilized to build predictive aggregation models for 25 mg/mL mAb formulations stored 9-months at 5 °C and 40 °C.

Permeability evolution of fractured coal subject to confining stress and true triaxial stress loading: experiment and mathematical model

The accurate elucidation and prediction of coal permeability evolution under stress loading conditions are crucial for coalbed methane production. In this study, flow experiments were conducted on six cylindrical coal samples and four cubic coal samples under both confining and true triaxial stress loading conditions, respectively. The structure and characteristic parameters of the fractures inside each coal sample were obtained using the computed tomography scanning system and image processing technologies. The coal permeability under both types of loading processes was calculated through the transient pulse method. A mathematical model was developed to assess the evolution of coal permeability under true triaxial loading based on the current true triaxial permeability model and fractal theory. The results revealed that during the confining pressure loading, the coal permeability decreased exponentially with effective stress and was effectively described using the SD model. Additionally, the coal permeability initially rapidly decreased, followed by a gradual decrease, and eventually stabilized at a constant value. Particularly, during the first three loading steps, the fracture aperture and corresponding permeability of the six cylindrical coal samples decreased by ∼51.79%–57.83% and ∼38.06%–42.12%, respectively. However, during the final three loading steps, the fracture aperture and corresponding permeability of the six coal samples decreased by ∼18.26%–23.08% and ∼22.15%–26.93%, respectively. Moreover, owing to the various crossing angles of complex fracture networks with each principal stress, the effect of each principal stress on the coal permeability evolution was highly anisotropic during triaxial stress loading. Particularly, the permeability of the ST1 sample decreased by 43.08%, 14.84%, and 42.08% during the loading of each principal stress. Similarly, the permeability of the ST2 sample decreased by ∼65.74%, 14.29%, and 19.97%. The permeability reductions for the ST3 sample were ∼34.03%, 55.85%, and 10.12%, while those for the ST4 sample were ∼35.97%, 46.51%, and 17.52%. The SD model failed to describe these anisotropic effects. Compared with the SD model, the improved model, based on the current true triaxial permeability model and fractal theory, effectively described the anisotropic effect of each principal stress on the permeability of coal samples with complex fracture networks under triaxial stress conditions.

Evaluation and Utilization of Flow Artifacts at CT.

Flow artifacts are commonly encountered at contrast-enhanced CT and can be difficult to discern from true pathologic conditions. Therefore, radiologists must be comfortable distinguishing flow artifacts from true pathologic conditions. This is of particular importance when evaluating the pulmonary arteries and aorta, as a flow artifact may be mistaken for a pulmonary embolism or dissection flap. Understanding the mechanics of flow artifacts and how these artifacts are created can help radiologists in several ways. First, this knowledge can help radiologists appreciate how the imaging characteristics of flow artifacts differ from true pathologic conditions. This information can also help radiologists better recognize the clinical conditions that predispose patients to flow artifacts, such as pneumonia, chronic lung damage, and altered cardiac output. By understanding when flow artifacts may be confounding the interpretation of an examination, radiologists can then know when to pursue other troubleshooting methods to assist with the diagnosis. In these circumstances, the radiologist can consider several troubleshooting methods, including adjusting the imaging protocols, recommending when additional imaging may be helpful, and suggesting which imaging study would be the most beneficial. Finally, flow artifacts can also be used as a diagnostic tool when evaluating the vascular anatomy, examples of which include the characterization of shunts, venous collaterals, intimomedial flaps, and alternative patterns of blood flow, as seen in extracorporeal membrane oxygenation circuits. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

A discrete approach for modelling the permeability evolution of granite under triaxial and true-triaxial stress conditions

In deep underground engineering, modelling the seepage characteristics of rock masses under complex stress conditions is crucial for the safe construction and stable operation of a project. The permeability of the rock mass is not only controlled by its internal pore structure but is also closely related to the deformation and fracturing of the rock. Although discrete methods offer advantages in describing the formation and development of fractures, these methods still face challenges due to the difficulties in establishing microscopic seepage models. This paper introduces a new hydro-mechanical coupled numerical model. In this model, a simple method is proposed to couple the Rigid-Body-Spring Method (RBSM) for rock deformation and fracturing simulation and the Equivalent Matrix-Fracture Network (EMFN) for seepage simulation. Subsequently, the model is employed to simulate the permeability of granite under three-dimensional stress conditions. The simulation results show that under hydrostatic stress conditions, the model accurately captures the decrease in permeability due to pore compression and collapse. Additionally, under deviatoric stress conditions, it reveals the stage-wise increase in permeability caused by granite fracturing. Finally, the model is applied to study the permeability evolution behaviour of rocks under true triaxial stress conditions. The results unveiled the significant impact of the intermediate principal stress on permeability evolution and revealing the microscopic mechanisms underpinning these effects. This paper paves a way for enhancing the application of discrete methods in forecasting the permeability evolution behaviour of intricate rock masses.

Three-dimensional numerical simulation on failure mechanical characteristics of fissured sandstone specimens under true triaxial conditions

Understanding intermediate principal stress influences on deformation characteristics and failure mechanism of fractured rock from deep engineering often necessitates long term on-site detection and complex experimental research, although very limited efficacy can be obtained. With presently available experimental data on conventional triaxial cuboid noncoplanar fissured sandstones, this study further investigated the effects of differential stress (σ2 − σ3) and rock bridge inclination angle (β30°, β60°, β90°, β120°, and β150°) on their damage evolution processes and failure modes based on 3D discrete element methods (PFC3D). Numerical simulation results indicated that the peak strength of the fissured sandstone under the same state of horizontal principal stress shows an overall increasing pattern with the increase of the inclination angle of the rock bridge, while its peak strain displays a decreasing and then increasing trend. Besides, in this work, five failure modes, nine crack types and two kinds of stress–strain curves are summarized which are significantly affected by the horizontal principal stress, rock bridge inclinations or cooperative interaction. Differential stress value of 15 MPa is an important threshold for determining the residual strength of the stress–strain curve from present to absent. The cracking and force chain evolution processes of five failure modes were analyzed in order to discover the corresponding failure mechanisms. Finally, differential stress and flaw inclination influences on rock mechanical parameters and failure behavior have significant implications for strategies of the design, operation, and maintenance of rock engineering under severe conditions in the underground.

A Test System for Microwave-Assisted Dual-Mode Mechanical Cutting of Hard Rock Under True Triaxial Compression

This paper introduces a test system for microwave-assisted dual-mode mechanical cutting of hard rock under true triaxial compression. The test system was developed by Northeastern University, China, to simulate the cutting and breaking of hard rock by a tunnel boring machine (TBM). The test system is mainly composed of a dual-mode mechanical cutting subsystem, a true triaxial loading subsystem and a high-power microwave presplitting subsystem. The system performs dual-mode cutting under true triaxial stress, applies a single sensor to monitor the three-dimensional force of the cutter head, and integrates the reduction in the vibration and resistance to torsion during the cutting process. Mechanical cutting tests of basalt under different amounts of microwave irradiation and true triaxial stress conditions were conducted in Chifeng, Inner Mongolia, China. The results showed that microwave radiation presplitting effectively improved the efficiency of mechanical rock breaking. However, after 180 s of microwave irradiation, true triaxial high stress inhibited the mechanical breaking of basalt in terms of the overall excavation depth. During the tests, each system performed stably. The test results verified the reliability of the test system.

True triaxial energy evolution characteristics and failure mechanism of deep rock subjected to mining-induced stress

In deep rock engineering, complex stress conditions are encountered, which leads to difficulties in engineering disaster prevention and control. To investigate the failure behaviors and mechanisms of deep rock mining, a series of tests was designed for mining-induced failure at different simulated depths using a multifunctional true triaxial geophysical (TTG) apparatus. The results showed that both the simulated depth and mining disturbance affected the deformation characteristics of the sandstone specimens. With increasing depth, the strength gradually increased. The peak strength increased fastest in the single-sided unloading failure test (SUFT) and slowest in the stress loading and unloading failure test (SLUFT). The failure mode also changed significantly. In the displacement loading failure test (DLFT), the failure mode gradually changed from tensile failure to shear failure. In the SLUFTs, the failure mode of the specimens changed from layer cracking to shear failure. In the SUFTs, the failure mode of the specimen transitioned from layer cracking to tensile shear failure and then to shear failure. Scholars have previously proposed an elastic strain energy calculation method for true triaxial stress conditions. An elastic strain energy calculation method applicable to different mining disturbance was proposed under true triaxial stress conditions, and the evolution characteristics of the work done, elastic strain energy, and dissipated energy were analyzed. Additionally, a method to quantitatively characterize the relationship between macroscopic cracks and dissipated energy was proposed, and microscopic fracture analysis was performed using scanning electron microscopy (SEM). Different depths and various types of mining-induced failure were fully considered, and the specimen deformation, failure type, energy evolution (including dissipation), and failure mechanisms were analyzed. The results can provide guidance for deep underground engineering projects.

Failure behaviors and acoustic emission characteristics of flawed granite of different grain sizes: Insights from true triaxial experiments with a free face

In this study, a group of experiments using true triaxial stress conditions with free face loading are performed on granite specimens with non-penetrating double flaws. The crack development and failure characteristics of these specimens are explored by integrating video of the free face and acoustic emission technology, with the combination of the four different intermediate principal stresses and three different grain sizes of the granite chosen as variables. First, surface flaws with a depth of 50 mm are found to have limited influence on the specimen’s failure mode. The intermediate principal stress has a greater effect as it inhibits the development of surface cracks; however, surface cracks develop much more readily in coarse-grained specimens than in other specimens. Second, when the intermediate principal stress exceeds 10 MPa, the rock burst failure phenomenon occurs in the specimen. Third, irrespective of changes in the intermediate principal stress and granite specimen grain size, the specimens primarily fail by tensile-shear failure and shear failure. Extending inward from the free face in the σ3 direction, according to the failure types, the failure types can be classified into tensile failure, shear failure, and tensile-shear failure. Finally, using the stress state synthesis method, the specimen’s stress state and crack distribution mechanism on the σ2 loading plane are analyzed.

Failure characteristic of fissured rock specimens under true triaxial unloading conditions

The failure characteristics of fissured rock specimens under true triaxial unloading conditions were investigated. The effects of the intermediate principal stress (σ2) on the stress–strain responses, failure modes, specimen strength, and acoustic emission (AE) cues were evaluated. It is found that the deformation in the direction of the minimum prnicipal stress decreases as σ2 increases to a certain value and then increases during unloading. The proportion of tensile cracks decreases as σ2 increases at values lower than 30 MPa but increases at values exceeding 30 MPa. The AE cues were analyzed to identify the failure modes of the specimens under unloading conditions. The percentage of tensile cracks is much higher than that of shear cracks at a low σ2. An increase of σ2 results in a decrease in the percentage of tensile cracks. However, the percentage of tensile cracks increases as σ2 exceeds a certain value. A damage model is proposed for predict the peak stress of the fissured specimens under unloading conditions.

A macro-mesoscopic constitutive model for porous and cracked rock under true triaxial conditions

The complex mechanical and damage mechanisms of rocks are intricately tied to their diverse mineral compositions and the formation of pores and cracks under external loads. Numerous rock tests reveal a complex interplay between the closure of porous defects and the propagation of induced cracks, presenting challenges in accurately representing their mechanical properties, especially under true triaxial stress conditions. This paper proposes a conceptualization of rock at the mesoscopic level as a two-phase composite, consisting of a bonded medium matrix and frictional medium inclusions. The bonded medium is characterized as a mesoscopic elastic material, encompassing various minerals surrounding porous defects. Its mechanical properties are determined using the mixed multi-inclusion method. Transformation of the bonded medium into the frictional medium occurs through crack extension, with its elastoplastic properties defined by the Drucker–Prager yield criterion, accounting for hardening, softening, and extension. Mori–Tanaka and Eshelby’s equivalent inclusion methods are applied to the bonded and frictional media, respectively. The macroscopic mechanical properties of the rock are derived from these mesoscopic media. Consequently, a True Triaxial Macro-Mesoscopic (TTMM) constitutive model is developed. This model effectively captures the competitive effect and accurately describes the stress-deformation characteristics of granite. Utilizing the TTMM model, the strains resulting from porous defect closure and induced crack extension are differentiated, enabling quantitative determination of the associated damage evolution.

Dynamic damage mechanism of coal with high true triaxial stress level subject to water jets

Deep mineral resources are abundant, and water jet technology has been proven to be an efficient means of developing this resource. In-situ stress is one of the prominent features in deep mines. However, the dynamic damage process of rock under the in-situ stress environment subject to water jets has not been revealed. Therefore, this study aims to fill this gap. For this study, coal breaking tests were performed to reveal the macro fracture patterns of coal under different true triaxial stress conditions. The results show that the bedding angle can significantly affect the coal-breaking characteristics, and when the bedding angle is 45° combines the advantages of length and aperture for jet drilling. When there is no geostress, the width of the cracks on the wall of the fracture pit is 3 μm, with a crack width of 7.5 μm at the bottom of the hole, and no through cracks generated under triaxial stress. Subsequently, further theoretical analysis and numerical simulation showed that the in-situ stress has a hysteresis and inhibitory effect on the dynamic damage evolution of jet coal breaking, hereby affecting the final fracture mode during the period. The results of this study will provide basic theoretical support for the jet drilling of rock in deep layered rock.

Effects of natural stiff discontinuities on the deformation and failure mechanisms of deep hard rock under true triaxial conditions

Stiff discontinuities have a significant influence on deep hard rock engineering disasters. To study the influence of these discontinuities on the deformation and failure mechanisms of deep hard rock during excavation, true triaxial tests are carried out on marble samples with natural stiff discontinuities; samples with different discontinuity inclination angles and thicknesses are tested under different true triaxial stress conditions. The experimental results show that the post-peak deformation and failure characteristics of a sample are significantly influenced by the inclination angle, thickness, and stress state of the stiff discontinuity. Under the conditions of a relatively high minimum principal stress, small intermediate principal stress, thick stiff discontinuity, and inclination angle close to the failure angle of the intact sample at the same stress level, the propagation and penetration of microcracks inside the sample are mainly controlled by the stiff discontinuity, and the sample is more prone to sudden and violent tensile failure along the stiff discontinuity. Based on these experiments, a sudden and violent failure tendency index of deep hard rock with a stiff discontinuity (ψ) is proposed to evaluate the impact of stiff discontinuities on surrounding rock failure in deep engineering, and the characteristics of ψ under typical stress levels are summarized. This research can provide a reference for the prevention and control of sudden disasters caused by stiff discontinuities in deep engineering.

Analisis Sistem Dan Prosedur Dasi Sebagai Sarana Proses Pembayaran Klaim Santunan Asuransi Sosial Pada Pt Jasa Raharja Atas Korban Kecelakaan Lalu Lintas Di Kabupaten Pati

This research aims to find out and analyze the Jasa Raharja Corporate Data (DASI) system and procedures for Jasa Raharja Pati Regency. The research method used by the author is descriptive qualitative with the aim of knowing or analyzing events that occur in the field according to existing facts so that the true conditions can be known. In this report, researchers provide information according to what happened to the research object. Based on the research results, the use of DASI has been fully implemented and provides convenience felt by employees, namely the level of quality and work efficiency produced even though sometimes there are still some system or network problems. Apart from that, due to the large number of accident victims received, services need to be improved. The author considers that to maximize work performance and productivity, it is necessary to require more professional human resources in carrying out DASI operations.

Hydraulic fracturing behavior of shale–sandstone interbedded structure under true triaxial stress conditions: A comprehensive experimental analysis

AbstractReservoirs characterized by shale–sandstone interbedded structures are extensively dispersed throughout China, and understanding the propagation mode of hydraulic fractures is a prerequisite for shale gas exploitation engineering. In this study, hydraulic fracturing tests were conducted using horizontal wells subjected to true triaxial compression conditions to elucidate the mechanism by which the initiated layer lithology and stress state influence the fracture morphology. Furthermore, the propagation mode of the fractures and the consequential effects on fracture network formation were investigated. The findings demonstrate four distinct interaction modes between the shale–sandstone interfaces and hydraulic fractures. The lithology of the initiated layer influences the fracture propagation trajectory, thereby affecting the propagation modes at the shale–sandstone interface and resulting in varying effects on layer penetration. The stress difference exerts a significant controlling influence on the fracturing behavior, enhancing the possibility of interconnecting multiple rock layers characterized by substantial stress differences.

Fracture propagation and failure mode characteristics of lamellar lacustrine shale under true triaxial compression conditions

Fracture propagation and failure mode characteristics of lamellar lacustrine shale under true triaxial compression conditions

Analisis Pemanfaatan Hutan Kota Giong Siu Kecamatan Sandubaya Kota Mataram sebagai Destinasi Wisata Edukasi

The existence of urban forests is very important in supporting climate, health and educational facilities in urban areas. The Giong Siu City Forest tourism was born from the creativity of the Babakan community, the Bahana Sustainable Tourism Awareness Group (Pokdarwis). Potential of Giong Siu City Forest as an educational tourism facility. This research really needs to be carried out, considering the function of urban forests which is really needed in educational institutions and the community, more specifically in forestry study programs where one of the subjects is urban forests. The method used is descriptive qualitative, where data collection is carried out by classifying primary data and secondary data. For secondary data, interviews are conducted with managers and visitors as samples which are carried out using the exidential technique, namely collecting as much data as possible from potential and presentative visitors. Data analysis through the existing facilities approach (amenities, accessibility, accommodation, attractions and activities) as a guide in presenting data scientifically and clearly regarding events in the field at the time of the survey (existing conditions) by telling the true conditions of the urban forest. The research results show that 70% of the information obtained from visitors about the existence of the Giong Siu City Forest is from friends, meaning that socialization is still done manually by word of mouth, only 10% is from social media (Instagram) and 20% is from residents who actually live there. around the Giong Siu City Forest. The results of interviews with Giong Siu tourism managers, who more often visit the Giong Siu City Forest, mostly students, students and kindergarten or elementary school children who do outdoor study, Giong Siu is usually busy on Saturday nights and Sundays, because it is not only a place To relax, Giong Siu City Forest itself has prepared several tents and hammocks which have been facilitated by the government for visitors who want to camp. Based on the description above, it can be concluded that the Giong Siu City Forest already has various adequate facilities as a recreation area, camping ground, flying fox, prayer room and bathroom. However, there are several shortcomings that the Giong Siu City Forest management must pay attention to, such as the addition of bathroom facilities that do not utilize the empty land that still exists around the Giong Siu City Forest.

A Critical Assessment on Calculating Vibrational Spectra in Nanostructured Materials.

Vibrational spectroscopy is an omnipresent spectroscopic technique to characterize functional nanostructured materials such as zeolites, metal-organic frameworks (MOFs), and metal-halide perovskites (MHPs). The resulting experimental spectra are usually complex, with both low-frequency framework modes and high-frequency functional group vibrations. Therefore, theoretically calculated spectra are often an essential element to elucidate the vibrational fingerprint. In principle, there are two possible approaches to calculate vibrational spectra: (i) a static approach that approximates the potential energy surface (PES) as a set of independent harmonic oscillators and (ii) a dynamic approach that explicitly samples the PES around equilibrium by integrating Newton's equations of motions. The dynamic approach considers anharmonic and temperature effects and provides a more genuine representation of materials at true operating conditions; however, such simulations come at a substantially increased computational cost. This is certainly true when forces and energy evaluations are performed at the quantum mechanical level. Molecular dynamics (MD) techniques have become more established within the field of computational chemistry. Yet, for the prediction of infrared (IR) and Raman spectra of nanostructured materials, their usage has been less explored and remain restricted to some isolated successes. Therefore, it is currently not a priori clear which methodology should be used to accurately predict vibrational spectra for a given system. A comprehensive comparative study between various theoretical methods and experimental spectra for a broad set of nanostructured materials is so far lacking. To fill this gap, we herein present a concise overview on which methodology is suited to accurately predict vibrational spectra for a broad range of nanostructured materials and formulate a series of theoretical guidelines to this purpose. To this end, four different case studies are considered, each treating a particular material aspect, namely breathing in flexible MOFs, characterization of defects in the rigid MOF UiO-66, anharmonic vibrations in the metal-halide perovskite CsPbBr3, and guest adsorption on the pores of the zeolite H-SSZ-13. For all four materials, in their guest- and defect-free state and at sufficiently low temperatures, both the static and dynamic approach yield qualitatively similar spectra in agreement with experimental results. When the temperature is increased, the harmonic approximation starts to fail for CsPbBr3 due to the presence of anharmonic phonon modes. Also, the spectroscopic fingerprints of defects and guest species are insufficiently well predicted by a simple harmonic model. Both phenomena flatten the potential energy surface (PES), which facilitates the transitions between metastable states, necessitating dynamic sampling. On the basis of the four case studies treated in this Review, we can propose the following theoretical guidelines to simulate accurate vibrational spectra of functional solid-state materials: (i) For nanostructured crystalline framework materials at low temperature, insights into the lattice dynamics can be obtained using a static approach relying on a few points on the PES and an independent set of harmonic oscillators. (ii) When the material is evaluated at higher temperatures or when additional complexity enters the system, e.g., strong anharmonicity, defects, or guest species, the harmonic regime breaks down and dynamic sampling is required for a correct prediction of the phonon spectrum. These guidelines and their illustrations for prototype material classes can help experimental and theoretical researchers to enhance the knowledge obtained from a lattice dynamics study.

An efficient drilling conditions classification method utilizing encoder and improved Graph Attention Networks

Identification of drilling conditions is paramount for ensuring safety and efficiency in drilling operations. Traditional methods, often based on manual analysis of drilling parameters and patterns by experts using empirical formulas, typically lack speed and precision in modern drilling procedures. To address this shortcoming, we have developed a sophisticated classification methodology that combines Encoder layers with improved Graph Attention Networks (GAT), aiming to precisely discern seven prevalent drilling conditions. Using an advanced expert empirical decision tree, we achieved superior accuracy in our dataset annotations. The model’s architecture integrates the K-nearest neighbors (KNN) algorithm for seamless integration between the Encoder layer and GAT networks. Sensitivity analyses pinpoint optimal feature parameters, leading to significant enhancements in model accuracy. Experimental outcomes show our annotation approach surpasses traditional techniques by 15.24%, achieving an accuracy of 96.73%. Additionally, our model boasts a recall rate of 94.22%, indicating high reliability in correctly identifying true positive drilling conditions, which is crucial for operational safety and decision-making in drilling scenarios. Characterized by its real-time capabilities, precision, and scalability, our model demonstrates promising potential for applications in practical drilling scenarios.