Energy Dissipation Method Research Articles

A preliminary experimental study on atomization rainfall properties by two-jet collision in high dam discharge

The energy dissipation method commonly employed for flood discharge in high dams involves the collision of jets in the air. This approach frequently results in the issue of flood discharge atomization. This study experimentally investigates the rainfall characteristics resulting from the interaction between a surface-orifice jet and a deep-orifice jet during high dam discharges. The research explores various flow rate ratios and collision angles of the two jets, focusing on the spatial distribution of rainfall intensity, as well as the size and velocity of droplets post-collision. The findings revealed that the rainfall distribution on the horizontal plane resembles a mushroom cloud, with the maximum rainfall intensity at the center. Increasing the collision angle between the jets significantly increases the dispersion range of atomized rainfall, while the maximum intensity decreases. Additionally, as the jet flow rate ratio increases, the dispersal range of rainfall initially expands before stabilizing, with relatively minor variations in intensity. Following a two-jet collision, the trajectory of the jet was derived, and the associated parameters were determined using experimental data. The probability distributions for droplet size and velocity closely approximated Gaussian distributions. The study also observed that the number of droplets per unit time, along with the ensemble-averaged diameter and velocity, initially increases and then decreases longitudinally. Meanwhile, the number of droplets per unit time gradually decreases in the lateral direction, while the ensemble-averaged diameter and velocity remain relatively constant. Furthermore, with an increase in the jet flow rate ratio, both the ensemble-averaged diameter and velocity of droplets follow a pattern of initial increase and subsequent decrease, while the collision angle has no significant impact.

Energy dissipation methods and protection device synergy strategies for offshore wind power receiving end surplus power

Abstract Firstly, a theoretical analysis of the fault ride-through scheme is carried out based on the land-side AC faults in the offshore wind power delivery system. According to the topological structure of the DC energy consumption device, the working mode and switching of the DC energy consumption device are analyzed and studied. Secondly, the DC protection action of offshore wind power flexible and direct transmission systems was studied, and the switching strategy of energy-consuming devices was determined. Then the impact of the switching of the energy-consuming device on the DC protection function was studied, focusing on the synergy between the DC overvoltage protection and the switching judgment voltage of the energy-consuming device. Finally, based on a typical offshore wind power flexing project, a system model is built in PSCAD/EMTDC to verify the effectiveness of the proposed synergy strategy.

Fracture properties of ultra-thin friction course mixture containing reclaimed asphalt pavement and glass fiber under monotonic and cyclic loading

Ultra-thin friction courses (UTFC) have demonstrated exceptional efficacy in the preventive maintenance of asphalt pavements. Despite this, research into the influence of reclaimed asphalt pavement (RAP) and glass fiber on the fracture behavior of UTFC mixtures under cyclic loading is sparse. In response, this study conducted both monotonic loading tests and tension cyclic loading tests on notched semi-circular specimens at a temperature of 25 °C to elucidate the impact of RAP and glass fiber on UTFC’s fracture resistance. The findings revealed that, during monotonic testing, the introduction of RAP appeared to bolster mechanical performance by increasing peak load and tensile stiffness index (TSI). However, RAP diminished the fracture energy, with the concurrent addition of RAP and glass fiber resulting in further compromise to fracture resistance. Conversely, in the cyclic loading tests operated under load control, the integration of RAP positively influenced fatigue life. Furthermore, the addition of 0.1 % glass fiber (identified as H-25R-0.1F) also improved fatigue life, highlighting its beneficial role in augmenting fatigue endurance. When compared to the mixture devoid of RAP, the inclusion of 25 % and 50 % RAP led to substantial increases in cumulative dissipated energy by 101 % and 398 %, respectively. These results suggest that both RAP and glass fiber have nuanced effects on the fracture and fatigue properties of UTFC mixtures, with potential implications for their application in roadway construction and rehabilitation. Minimum rate of cumulative dissipated energy change (RCDEC_min) could be used to characterize the fatigue performance. The lower the RCDEC_min, the larger the fatigue life. There existed a power law relationship between RCDEC_min and fatigue life, which was independent of the mixture type. Compared to the cumulative dissipated energy method, the maximum displacement method may be more suitable to characterize the damage evolution during the fatigue test.

Comparison of collision dynamics of soccer balls with energy dissipation method

This study aimed to understand the collision characteristics of different soccer balls by determining energy dissipation (ED) during collisions. Soccer balls from five different brands were kicked towards a framed tempered glass. The kicks were performed with the balls inflated under three inner pressure conditions. The motion of each ball was recorded using two high-speed cameras at 6000 Hz. The contact surface area (CSA), ball indentation amount (IA), reaction forces (RF) and energetic coefficient of restitution (CoR) during contact were calculated via image processing methods. A new methodological approach was developed to determine the ED during the collision (EDDC). The accuracy of the estimated RF was validated using force plate data, and the CSA values validated the calculated IA. The EDDC were then reduced to a single value to compare with the CoR values obtained using the traditional formula. Differences between CoR and EDDC were statistically tested. One-way ANOVA tests were performed separately to compare the effect of the ball brand on the IA and EDDC for each inner pressure condition. The CoR and EDDC showed no significant difference, proving that the developed method is a valid measure of ED. At 1.0 bar inner pressure, IA and EDDC showed significant differences according to the brands. EDDC, depending on the ball quality, decreased at higher inner pressure values regardless of the brand. Consequently, the present study exhibited that ball quality becomes a critical factor in collision dynamics at high inner pressure values, considering that ball inner pressure may vary between 0.6 and 1.0 bar in official soccer matches.

Plastic and damage energy dissipation characteristics and damage evolution of Beishan granite under triaxial cyclic loading

The damage and failure of rock under triaxial stress is an irreversible process of energy dissipation, which mainly includes plastic energy dissipation and damage energy dissipation. However, it is difficult and rare to separate plastic energy dissipation and damage energy dissipation and to conduct relevant research on this basis. In this work, a loading control method with a combination of load (0.5 kN/s) and circumferential deformation (0.01 mm/min) was used, and triaxial cyclic loading and unloading tests under five different confining pressures were performed on granite from the Beishan site area of China's high-level radioactive waste repository. The results indicate that the angle between the main fracture surface and the longitudinal axis increases with the increase of confining pressure. According to the characteristics of the stress–strain curve and energy dissipation, the test process can be divided into five stages: the initial compaction and elastic stage, the stable crack growth stage, the unstable crack growth stage, the postpeak unstable fracture stage and the residual stress stage. Importantly, a separate determination method of plastic energy dissipation and damage energy dissipation was proposed, and the evolution characteristics of plastic energy dissipation and damage energy dissipation were revealed. The ratio of plastic energy dissipation to input energy decreases slightly in the initial compaction and elastic stage, stabilizes at a low level in the stable and unstable crack growth stages, increases significantly in the postpeak unstable fracture stage and remains at a high level in the residual stress stage. Meanwhile, the ratio of damage energy dissipation to input energy increases slightly before the unstable crack growth stage, increases abruptly at the end of the unstable crack growth stage and the initial part of the postpeak unstable fracture stage, then declines rapidly, and finally remains at a low level. Furthermore, the qualitative and quantitative research results of damage evolution show that the plastic shear strain and damage variable established by damage energy dissipation can qualitatively and quantitatively describe the damage evolution of Beishan granite respectively. Finally, the verification results of Beishan granite and two other rock types show that the separation method for calculating plastic energy dissipation and damage energy dissipation proposed in this work has good adaptability, and the qualitative damage development analysis based on plastic shear strain can be verified and supplemented with the quantitative damage development analysis based on energy theory.

Stability analysis of energy dissipation mechanisms in rocks surrounding circular opening

This study analyzes the stability of surrounding rock for a circular opening based on the energy and cavity expansion theory, and regards the surrounding rock failure of circular opening as an unstable state driven by energy. Firstly, based on the large-strain cylindrical cavity contraction and energy dissipation method, the deformation caused by the excavation of surrounding rock is regarded as the cylindrical cavity contraction process. By introducing the energy dissipation mechanism, the energy dissipation solution of cylindrical cavity contraction is obtained. The energy dissipation process of surrounding rock is characterized by the strain energy changes in the elastic and elasto-plastic regions of this cavity contraction analysis. Secondly, the deformation control effect of support and surrounding rock parameters on the energy dissipation of surrounding rock is studied based on the energy dissipation solution of surrounding rock under support conditions. Finally, the effectiveness and reliability of the analytical approach was demonstrated by comparing the support design results with those in the literature. The research results indicate that the three-dimensional mechanical properties and dilatancy angle of rock and soil mass have a significant impact on the energy support design of surrounding rock. This study provides a general analysis method for the stability analysis of surrounding rock of deep buried tunnels and roadway.

Fatigue life prediction of welded joints under variable stress ratios based on the energy dissipation method

Fatigue life prediction of welded joints under variable stress ratios based on the energy dissipation method

Integrating thermodynamics and mathematical modelling to investigate the stoichiometry and kinetics of sulphide oxidation-nitrate reduction with a special focus on partial autotrophic denitrification

In the present study, the stoichiometry of the Sulphur Oxidizing-Nitrate Reducing (SO-NR) process, with a focus on Partial Autotrophic Denitrification (PAD), has been evaluated through a thermodynamic-based study whereas a model-based approach has been adopted to assess process kinetics. Experimental data on process performance and biomass yields were available from a previous work achieving efficient PAD, where a biomass yield of 0.113 gVSS/gS was estimated. First, the free Gibbs energy dissipation method has been implemented, in order to provide a theoretical framework exploring the boundaries for sulphur oxidizing biomass yields. Second, a screening of available mathematical models describing SO-NR process was conducted and five published models were selected, in order to assess the most suitable model structure for describing the observed PAD kinetics. To the best of our knowledge, none of reported biomass yields are estimated in systems operating PAD as the main process and, analogously, none of the proposed models have been applied to case studies aiming at partial denitrification only. The work showed that the very low biomass yield of 0.117 ± 0.007 gVSS/gS, observed in a PAD system in our previous work, suggests that the conditions applied to achieve partial denitrification resulted in a high energy-dissipating metabolism compared to complete denitrification applications. Models’ analysis revealed that nitrite accumulation can be described by a classical Monod kinetics if different μmax are adopted for each intermediate reaction, with Theil Inequality Coefficient values lower than 0.21 for both NO3− and NO2−. Nonetheless, adopting Haldane-type kinetics for nitrite uptake inferred higher identifiability to the model structure, resulting in confidence intervals below ±10% for all the parametric estimations. The thermodynamic and modelling outcomes support the experimental results obtained in the reference study and the critical comparison of model suitability to represent PAD process is believed pivotal to pave the way to its real-scale implementation.

Research on the Vehicle Steering and Braking Stability Region

Solving the stability region in the plane motion of vehicles has become a hot research topic in vehicle handling stability under extreme conditions, but there is still a lack of research on the stability region under steering and braking conditions. In this paper, a five-degree-of-freedom (5DOF) nonlinear dynamic model of a vehicle with braking torque introduced is established, and the model is transformed into an equivalent system by using the D’Alembert principle. Then, the equilibrium points of the equivalent system are solved by using an improved hybrid algorithm combining the genetic algorithm (GA) and sequential quadratic programming (SQP) method. According to the bifurcation characteristics of the equilibrium points, the boundary of the stability region at the given initial longitudinal velocity is determined, and the three-dimensional stability region is fitted. Finally, the stability region of the equivalent system and the original system are analyzed by the energy dissipation method, and the stability region determined by the equilibrium point bifurcation method is verified by simulation. The results show that as the braking torque increases, the number of equilibrium points increase to three from one, the equilibrium bifurcation method proposed in this paper can effectively solve the stability region of the equivalent system, and the solution results are consistent with the original system stability region. When the limited braking torque is 500 N·m and the initial longitudinal velocity increases from 30 m/s to 50 m/s, the absolute value of the front wheel steering angle at the boundary point changes from less than 0.02 rad to more than 0.02 rad.

Damage Characteristics and Energy Evolution of Bituminous Sandstones under Different Cyclic Amplitudes

In many underground engineering projects, rocks are often subjected to cyclic loading and unloading, such as repeated excavation of roadway surrounding rock, which will lead to damage to underground rocks, and the energy of rocks also changes. Therefore, to study the energy evolution and damage characteristics of rocks under cyclic loading and unloading, different cyclic loading and unloading tests of bituminous sandstones under constant amplitude were conducted. Under cyclic loading and unloading, the lower limit stress was 40% of the rock peak intensity, the cyclic amplitude was 20–40% of the peak intensity, and the number of loading–unloading cycles was 10–30. The quantitative characterization of the damage degrees of bituminous sandstone was realized by the ultrasonic wave velocity and elasticity modulus methods. The energy evolution and damage characteristics of bituminous sandstone under different amplitudes and number of loading–unloading cycles were investigated through the energy dissipation method. Results showed that under cyclic loading and unloading, the ultrasonic wave velocity and elasticity modulus of bituminous sandstone decreased gradually; The damage variable shows a trend of rapid and then stable growth and has a power function relationship with the number of cycles; The input energy density and dissipation energy density curves were in L-shaped distribution, whereas the elastic energy density remained stable. The results of this study can provide some theoretical references to underground engineering construction.

Perforation of carbon fiber reinforced plastic laminates struck transversely by hemispherical-nosed projectiles

This study focuses on perforation of carbon fiber reinforced plastic (CFRP) laminates struck transversely by hemispherical-nosed projectiles. Global deformation with local rupture failures for thin laminates and localized response failures for thick laminates are two common categories of the ballistic perforation of CFRP laminates. An analytical model is proposed considering these two failure modes and their transition conditions. The ballistic limit predicted for laminates in global deformation with a local rupture failure mode is given based on the energy dissipation method, and an ultimate perforation failure criterion is derived based on the bottom surface tensile fracture of the laminate. A critical transition condition of the two failure modes is obtained by combing the localized response failure model and Von Karman’s critical impact velocity concept. Model predictions agree with the experimental and numerical results regarding ballistic limits in a wide ratio range of laminate thickness H and hemispherical-nosed projectile diameter d.

Simplified Estimation Method of Plastic Energy Dissipation for MDOF Systems Using Force Analogy Method

Plastic energy dissipation is a key factor in the response of inelastic structures subjected to seismic input, and is often regarded as a primary source of structural damage due to the inelastic deformation of structural components. Accurately predicting a structure’s plastic energy dissipation is essential for efficient energy-based design and seismic assessment. While a single-degree-of-freedom (SDOF) system provides a simple and effective method for estimating plastic energy dissipation, few studies have explored the use of nonlinear analysis methods or equivalent SDOF systems for this purpose. Based on the principle-of-force-analogy method, firstly, the formulas of plastic energy dissipation of a multi-degree-of-freedom (MDOF) system and its equivalent SDOF system were established. Secondly, two estimation methods of plastic energy dissipation of MDOF systems were proposed. Finally, numerical simulations were performed on several multi-story and high-rise structures with varying heights and spans to compare the plastic energy dissipation of MDOF systems and the equivalent SDOF systems of different modes. The simulation results demonstrate that the proposed methods and formulas accurately estimate plastic energy dissipation in multi-story and high-rise structures, while also requiring fewer calculations and less storage.

Frictional vibration behaviors of a new piezo-damping composite under water-lubricated friction

Water-lubricated bearings have become an important component of marine propulsion systems due to the requirements of environmental friendliness and concealability. However, water-lubricated bearings are often subjected to bending stress, additional stress, frictional resistance and other multi-factor effects, resulting in boundary friction or even dry friction on the friction interfaces when encountering unique working conditions such as engine start-stop, steering, low-speed, and heavy-load. The severe frictional processes often induce vibration behaviors and generate frictional noise, which seriously weakens the sound concealment performance and service life of marine propulsion systems. Therefore, it is urgent to improve the vibration and sound pressure behaviors of the composite bearings under water-lubricated conditions. In this study, novel barium titanate/carbon black/polyurethane composites (BaTiO3/CB/PU) are fabricated and then explored the damping capacities and tribological properties of the new polymers. The results showed that the BaTiO3 concentrated on transforming the mechanical energy generated by frictional vibration into electrical energy which generates the thermal energy. The water cooled the frictional heat and the piezo-damping heat. This energy dissipation method increased the damping capacity to reduce the vibration and noise behaviors induced by friction. The composite with 3.0 wt% BaTiO3 performed the highest loss factor under the operating temperatures and presented the best frictional vibration reduction properties. The knowledge obtained in this study is useful not only to explore a new piezo-damping composite, but also to provide a theoretical basis for developing higher performance polymer-based water-lubricated bearing.

Simulation and Verification of Involute Spline Tooth Surface Wear before and after Carburizing Based on Energy Dissipation Method

This work studies the tooth surface wear of floating involute spline couplings. Based on the energy dissipation method, this study takes the floating involute spline couplings as the research object, divides the whole wear cycle into three wear stages and analyzes its wear mechanism, and proposes a wear prediction model suitable for floating involute spline couplings. By using Abaqus, the simulation of the involute spline couplings before and after carburizing was carried out when the floating distance was 0 mm, 0.3 mm and 0.6 mm, respectively. The wear depth of each tooth was compared and analyzed, and the axial and radial distributions of the wear on the tooth surface of the involute spline couplings were explored. Finally, the floating involute spline couplings test bench was used to verify the spline wear before and after carburizing. The results show that with the increase in floating distance, the wear of the tooth surface also increases, and the upper edge of the tooth surface is seriously worn. Through the comparative analysis of the spline tooth surface wear before and after carburizing treatment, it can be seen that carburizing treatment can effectively reduce the wear degree of the spline couplings tooth surface and improve the service life of the spline couplings, but at a high floating distance, carburizing treatment has no significant effect on improving the performance of the tooth surface.

Fatigue durability test of quasi-isotropic carbon/epoxy laminates in marine environment

Fiber-reinforced polymer (FRP) composites are utilized as a substitute material for metal structures in maritime industries. The durability of composites depends on varying harsh marine environments. The continuous exposure of FRPs to the harsh marine environment affects their static and dynamic properties. In this study, the impact of moisture absorption on the fatigue characteristics of autoclave-cured quasi-isotropic carbon/epoxy laminates is examined. Specimens were aged in artificial seawater under ambient, sub-zero, and humid conditions for 365 d. The fatigue test was conducted at different stress levels on aged laminates. The S-N curve, stiffness degradation, damage accumulation, and rate of damage growth using energy dissipation method were evaluated based on the experimental results. The results showed that fatigue property of quasi-isotropic carbon/epoxy specimens largely depends on aging conditions. The S-N curve of aged specimens showed a greater fatigue life at higher stress levels than the pristine specimen. Under different aging conditions and varying stress levels, specimens exhibited a standard damage curve. A total of 60–70% damage was developed during the initial stages of fatigue loading. The presence of moisture, multiple cracks, and interphase debonding between fibers and matrix were responsible for the reduction in fatigue life of quasi-isotropic carbon/epoxy specimens.

A new analytical method for calculating the strain of oil and gas pipeline under a normal fault dislocation

AbstractOil and gas pipelines that go through an active normal fault often deform largely and cause serious disasters. On the basis of the beam theory of the elastic foundation and assuming a shape function for the deformed pipeline, a new analytical method is proposed to calculate the pipeline strain under a normal fault. The length of the deformed pipeline is calculated by using a simplified structural mechanical model. Moreover, a three‐dimensional solid finite element model (3D FEM) is developed to calculate the pipeline strain under different working conditions. The developed analytical solution and the numerical results of 3D FEM are compared with the results of the two traditional methods (the dissipated energy method and the Karamitros method). The strain development law predicted by the proposed method and the 3D FEM is in good agreement with that of the dissipated energy method and the Karamitros method. Compared with the existing models, the new analytical method is simpler and more efficient.

Study on added damping due to resistive shunting on cantilever, simply supported beam, and effect on the variation of amplitude at resonance

The current work determines the piezoelectric damping of resistively shunted beams induced by resistors through joule heating. To predict this damping, a piezoelectric patch [Formula: see text] is attached to the surface of a cantilever beam. The current work emphasizes the effect of various parameters on damping added to the cantilever beam through the energy dissipation approach. This work analyzes different methods for predicting added damping. Results from different approaches rely on the base structure modeshape. Using the energy dissipation method from voltage generation, estimated added damping, included a stepped beam model to account for the curvature of the beam with PZT. Further, the same is validated with existing literature and found to be consistent. With the energy dissipation approach, including the stepped beam model compared with experimental literature data, the accuracy of the adopted beam model is validated. Few critical observations were made, such as the location of the PZT patch plays a vital role in determining the required added damping for a particular mode. This optimal location was the nodal location of the other modes. The location of the piezoelectric patch is an important parameter to achieve the required added damping for a particular mode. The optimal location of PZT to achieve maximum added damping for a particular mode may lie at the nodal location of other modes. This optimal location is addressed by rigorous experiments on a simply-supported beam initially and further correlated to a cantilever beam with the help of an energy dissipation approach. The energy dissipation model is correlated and validated for cantilever beam straight PZT on cantilever beams and a simply supported beam. In practical situations, in ambient conditions, environmental effects may result in a change of resonant frequency and thus amplitude. This variation may alter the base and shunt damping performance attributed to air damping. We have experimentally investigated the influence of air damping for base damping (inherent) and added damping (PZT).

The relationship between storage-dissipation-release of coal energy and intensity of induced charge

Using uniaxial compression experiments, the evolution characteristics between energy and induced charge in each stage of coal deformation and failure are studied. Further, the relationship of energy conversion in the process of coal failure is analyzed. The calculation methods of energy storage, dissipation, and release of coal are proposed. The relationships between induced charge intensity and factors, including storage of elastic strain energy, increment of elastic strain energy, increment of dissipated energy, released energy, accumulated dissipated-released energy, are studied. A theoretical model of induced charge based on dissipated energy and released energy is established. The monitoring test of induced charge under the mine is conduced. The results show that the induced charge intensity is not related to the accumulation of elastic strain energy, but positively correlated to the dissipation and release of elastic strain energy. The induced charge intensity is not significantly correlated with the cumulative dissipated-released energy, but is significantly correlated with the slope of the cumulative dissipated-released energy curve and its variations. Especially when the escalation effect shows, the induced charge intensity accordingly increases in an abrupt manner. When the increment of dissipated energy rises to a certain degree, the intensity of induced charge suddenly increases. When the released energy suddenly increases, if the major part converts into the kinetic energy of coal chips and particles, a violent ejection phenomenon occurs, the induced charge intensity suddenly increases. The induced charge intensity is positively correlated with the increment of dissipated energy and the sudden increase of released energy. The higher the stress concentration degree and the greater the influence of mining for coal-rock, the larger amount of energy is dissipated and released, and thus the greater intensity of induced charge is monitored. The study can provide a theoretical basis for the monitoring and early warning of coal-rock dynamic disaster.

Hydrodynamic design and analysis of a hybrid-driven underwater vehicle with ultra-wide speed range

This paper presents a hybrid-driven underwater vehicle with ultra-wide speed range, which combines the conventional autonomous underwater glider with a shaftless propeller. By designs of low-resistance structures in wide speed range, the vehicle has a low-speed gliding mode within 3 kn driven by buoyancy, and a low-medium-high speed navigation mode up to 30 kn driven by the propeller. In order to analyze the effectiveness of the structure designs, an analysis method of the flow energy dissipation (FED) is proposed. By solving the cumulative function of the FED, this method can quantitatively characterize the influence of the vehicle's local structures on navigation power consumption. On this basis, the hydrodynamic numerical models for the two modes are established by the computational fluid dynamics (CFD) methods. The numerical analysis indicates that this vehicle has a good lift-drag ratio in glide mode and a superior fluidity in propelled mode. It can maintain low resistance and low power consumption in both modes. Finally, the numerical models are verified to be accurate by prototype tests. This vehicle can provide reference for the designs of the integrated underwater platform with wide speed range and multi missions.

Analysis Deformation Failure Characteristics and the Energy Evolution of Varying Lithologies under Cyclic Loading

Deep underground engineering often utilizes cyclic loading. To understand the deformation and damage characteristics of rock under cyclic loading conditions, cyclic loading tests of three different specimens with varying lithology were performed. The dissipated energy method was used to analyze the magnitude of damage and rock failure characteristics during the energy evolution process of cube specimens. The results indicated that the modulus of elasticity of three lithologies were stable prior and subsequent to cyclic loading. While the cyclic loading profile improved the rock’s resistance to deformation, it increased the internal mesostructure defects. Rock damage caused by the cyclic loading reduced the uniaxial compression strength. This was especially true for coal samples. For coal samples, these observations were consistent with internal coal damage calculated by analysis. Under the same lithology and different loading modes, rock damage was caused by cyclic action, and the elastic strain energy released by instantaneous unloading of rock samples with significant damage was reduced. The rupture magnitude for cyclic loading was observed to be less than that of uniaxial compression. Under cyclic loading and varying different lithologies, sandstone absorbed the most energy, resulting in a larger final fracture magnitude compared to other lithologies.