Internal Pressure Research Articles

Optimization of the annulus space structure for hydrocyclone separation of rubber particles based on NSGA-II and GMDH

Rubber particles produced during industrial rubber manufacturing pose significant health and environmental risks. Due to their small size, these particles are difficult to efficiently separate and recover. Previous studies have shown that increasing the annular gap can reduce the circulation of small particles within the hydrocyclone. However, the optimal design of the annular gap structure has not been thoroughly investigated. This paper focuses on the structural optimization of the annular space, dividing it into three parts: annular width (w), insertion depth (L), and diameter (Dh). Single-factor analysis reveals that an increase in annular width lowers the internal pressure field; an increase in annular insertion depth causes vortex movement downward, reducing the separation zone; and an increase in annular diameter generates vortices within the annular gap. Multi-factor analysis using GMDH and NSGA-II shows that the GMDH model has excellent predictive capability, with R2 values of 94.23 % for separation efficiency and 92.77 % for pressure drop. The optimal structure obtained from NSGA-II is the C-type hydrocyclone (Dh: 7.45, L: 7.2, w: 3.96), with separation efficiency and pressure drop of 85.72 % and 0.1649 MPa, respectively. The optimized hydrocyclone shows improvements of 4.46 % in separation efficiency and 8.89 % in pressure drop compared to the non-optimized performance. This study applies genetic algorithms to the structural optimization of the annular gap, providing theoretical insights into the design of hydrocyclone annular gap structures.

Effect of High Temperature on Micro-Structure and Mechanical Properties of Fiber-Reinforced Cement-Based Composites

Synthetic fibers can effectively inhibit the formation and propagation of micro-cracks in concrete, significantly reducing the number and scale of cracks within the concrete matrix, thereby enhancing the concrete’s crack resistance and seepage prevention capabilities. In this study, two types of synthetic fibers, polyvinyl alcohol (PVA) and polypropylene (PP), were incorporated into cement mortar to investigate their microstructural evolution at elevated temperatures and their influence on the mechanical properties of the mortar. Both fibers were added at a volume content of 0.5%. The mortar samples were subjected to the following temperature conditions: 20 °C (ambient), 200 °C, 400 °C, and 500 °C. The results indicate that the synthetic fibers employed in this study improved the tensile properties of the mortar at room temperature (20 °C). This enhancement persisted up to 400 °C, beyond which, at 500 °C, the mechanical properties of the fiber-reinforced mortar deteriorated significantly. At 400 °C, the tensile strength of the PVA group increased by approximately 16% compared to the unblended fiber group (JZ) and by about 45% compared to the PP group. After treatment at 500 °C, the tensile strength of mortar specimens in the PVA group and the PP group decreased by 36.47% and 24.14%, respectively, compared with that at 20 °C. The porous structure formed due to the high-temperature ablation of the synthetic fibers contributed to relieving the internal pressure within the mortar.

Failure behavior and probabilistic safety assessment of containment structure under internal pressure considering time-varying prestress loss

This paper adopts a refined method to calculate the prestress loss of containment and evaluates the impact of time-varying effects on the mechanical properties and safety of containment under accident pressure. Firstly, a new method for converting the commonly used creep model into the Kelvin chain creep model is proposed, and rate-type constitutive relationships considering time-varying factors are established. Utilizing the developed subroutine scripts, these constitutive relationships are incorporated into the ABAQUS platform. Subsequently, the prestress losses of containment at different service times are calculated. Finally, the failure behavior and the probabilistic performance of containment under prestress loss and internal pressure conditions are systematically discussed. Results show that the proposed method exhibits high applicability, and the fitted creep compliance function based on the Kelvin chain model agrees well with the original creep compliance function. For the investigated containment, the time-varying prestress loss is most pronounced in the horizontal tendons near penetrations. Under design pressure, the containment remains elastic for all investigated prestress loss conditions, but the structural deformation, steel liner strains, and principal tensile stresses in concrete increase with the increase in time-varying prestress losses. At the limit state, greater time-varying prestress loss makes the containment more prone to functional failure at lower internal pressures. The time-varying prestress loss has a significant impact on the fragility and reliability of the penetrations in containment, while its impact on regular segments is relatively small.

Suppression of dead zones in slot-coated organic thin films by monitoring of meniscus formation for OLEDs

There inevitably appear dead zones in organic thin films fabricated by sheet-to-sheet slot-die coating because a coating start varies and the recovery time of internal pressure in slot-die head differs for each coating, resulting in poor coating repeatability. Slot-coated thin films within dead zones are thinner or thicker, possibly causing non-uniform light emission from solution-processable organic light-emitting diodes (OLEDs). To tackle it, we have devised an automatic coating start method based on the monitoring of meniscus formation. It automatically starts coatings when the cross-sectional area of meniscus reaches a certain optimal value in such a way that the start of each coating is kept unchanged. It is found that high-viscosity (4800 cPs) polydimethylsiloxane (PDMS) requires a longer time for the internal pressure of slot-die head to reach a steady state than low-viscosity (80 cPs) poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). It can be reduced to a great extent by applying a method of discharging the solution in advance (pre-discharging scheme). Compared with high-viscosity PDMS films, low-viscosity PEDOT:PSS films are shown to have longer dead zones and poorer repeatability due to the fact that the dead zone of relatively thin films varies sensitively to a small change in the coating start timing. With this scheme, we have successfully fabricated a highly uniform OLED device with no dead zones in the emission area.

Internal tension or external pressure? Study on the influencing factors of the diffusion of education policies for older adults in China – Based on the analysis of China’s provincial panel data from 2016 to 2023

ABSTRACT The development of education for older adults through policy measures has become an important means for governments to actively cope with population aging. Taking the number of education policies for older adults adopted in 31 provinces of China from 2016 to 2023 as an example, this study empirically analyzes the factors influencing the diffusion of education policies from dimensions of internal tension and external pressure. The results showed that the level of economic development, natural population growth rate, older adults dependency ratio, child dependency ratio, illiterate population over 15 years old, number of local libraries inside the province and the adoption of education policies for older adults in adjacent provinces significantly affected the adoption of education policies for older adults in each province. After the introduction of regional variables, it is found that there are significant differences in the adoption of education policies for older adults by provincial governments in different regions of China. The policy responsiveness of eastern provinces is the best, followed by the central, and the western is the worst. The above results indicate that provincial governments in China are not only affected by the supply level of education services for older adults and their service demand within the province, but also affected by the adoption behavior of other provinces when making decisions, which is the result of rational thinking and competitive pressure. The above results provide China’s experience for the diffusion and implementation of education policies for older adults in a wider range.

Design and material optimization of carbon fiber composite winding reinforcement layer for vehicle Type-IV hydrogen storage vessels

Due to the safety, reliability, and high hydrogen storage density of vehicle Type-IV composite overwrapped pressure vessels (COPVs), the Type-IV COPVs are currently the preferred choice for vehicle hydrogen storage vessels. The reinforcement layer bears 80 % to 90 % of the internal pressure load, and it accounts for a significant proportion of the total cost and weight of Type-IV COPVs. Thus, the reinforcement layer is the key problem in the design and optimization of the vehicle Type-IV COPVs. Firstly, this paper proposed a design method for vehicle Type-IV COPVs considering the strength and stiffness of reinforcement layer, and created the hydrogen storage vessel scheme. Then, the stress and strain of vehicle Type-IV COPVs under working and blasting internal pressure were analyzed by finite element simulation. Finally, the genetic algorithm was used to find the best carbon fiber for vehicle Type-IV COPVs. The results show that the scheme designed by the method in this paper can meet the requirements of vehicle use; The carbon fiber modulus most suitable for car hydrogen storage bottle winding is 288.8 GPa, and the weight of the reinforcement layer is reduced by 32 % compared to the T700S carbon fiber composite wound vessel.

Theoretical and FEA investigation of the mechanical behaviour for offshore LCO2 floating hose

Injecting liquid CO2 (LCO2) into the seabed for storage utilizing an offshore platform to achieve offshore storage of CO2 is one of the effective measures to realize the reduction of CO2 emissions. To solve the difference in motion characteristics between the LCO2 carrier and the receiving platform due to wind and wave currents, floating hoses can be employed as the pipeline in the CO2 transportation. In this study, an LCO2 floating hose based on the structural form of steel wire reinforced thermoplastic composite pipe is proposed. A mechanical model for this hose is developed to analyze the tensile mechanical properties. It is verified that the method is reliable by comparing with the published experimental results of composite hose containing 4 layers of aramid fiber reinforced layers with a maximum error of 11.48%. A comparative analysis was also carried out by finite element analysis (FEA) with a maximum error of 10.67%. On this basis, the damage states of the hose under internal pressure, tension, bending and torsion load were investigated to analyze mechanical properties. The ultimate tensile load capacity, ultimate bending radius and ultimate unit torsion angle are 463 kN, 1.64m and 14°/m, respectively. The components most prone to failure under different loads were clarified. This study can provide technical reference for the design of floating hoses for offshore LCO2 storage and transportation.

Pattern of eye disease among obese population in Erbil city, Iraq

Background and objective: Obesity is a multifactorial disease. It is a multifactorial pathology that can be related to an altered nutritional behaviour or secondary to genetic, hypothalamic, iatrogenic or endocrine diseases. Obesity and visual acuity are negatively correlated, obesity may be linked to dysfunction of the mechanical and vascular components of the eye. The aim of the study is to find out the impact of obesity on eye health and the pattern of eye disease. Methods: Across-sectional study was conducted in the Ophthalmology Department/ Erbil Teaching Hospital during the period from 1st of August 2021 to 31st of March 2022. A simple random sampling method was adopted, and a total of 300 participants with an age of more than 18 years old were enrolled. Results: The percentage of cataract, glaucoma, age-related maculopathy, papilloedema, keratoconus, and retinal vein occlusion was higher in the case group than in the control group. Obesity is a significant risk factor for cataracts, age-related maculopathy, and papilloedema, while it was insignificant regarding keratoconus and retinal vein occlusion. The mean of internal ocular pressure and central corneal thickness was higher in the case group compared to the control group. Conclusion: The prevalence of ocular disease was higher among the obese population than in those with normal weight. Obesity is a significant risk factor for ocular disease. Age and gender represented additional risk factors in some of the ocular diseases in obese people.

Numerical investigation into the effects of aft deck angle on the flow characteristics of a serpentine nozzle

For modern military aero-engine, the serpentine nozzle with aft deck is deployed to meet the requirements of stealth and integrated design. Different from existing studies which emphasize the rectangular nozzles and corresponding infrared radiation impact, the effect of the aft deck angle on flow characteristics of serpentine nozzles with a focus on the internal flow, the shock system, the jet’s evolution, and the performance parameters are systematically investigated in this paper. This study is carried out through three-dimensional numerical simulations, which are validated by the experiment. The results show that the aft deck with different angles has a significant impact on the overall flow characteristics, such as the static pressure and the three-dimensional shock system, as a result of the asymmetry and the contraction/expansion effects on the jet. Specifically, upward-deflected aft decks lead to a re-compression effect and the variation of the internal static pressure value can be up to 7%, whereas for downward-deflected aft decks, the effect on the internal flow can be neglected in under-expansion conditions. In addition, the aft deck angle and the extent of boundary layer separation greatly affect the thrust performance and the vortex evolution, which determines the downstream evolution of the jet cross-section. Effective thrust coefficient is closely tied to the thrust vector angle, with the coefficient reaching its zenith when the thrust vector angle is closest to 0°. This study reinforces understanding of the interrelated problems and may facilitate the development of the optimal aft deck angle for various applications.

Influence of crossing fault position and site soil on the mechanical properties of bellows joint connected buried pipelines under direct shear

Buried pipeline systems are vulnerable to joint damage in earthquakes. Previous studies have shown that bellows joints are effective in increasing deformation capacity and reducing the axial force of the main pipeline. However, the effectiveness of bellows joints in enhancing the deformation capacity of the pipelines is affected by the location of the crossing fault and the soil at the site. This paper constructs and validates a finite element model of a buried steel pipeline connected by a bellows joint using ABAQUS to investigate this issue. The effects of fault location, soil properties, and internal pressure on the bellows joint connected pipelines were analyzed using a finite element model. The results indicate that the bellows joints exhibit the best energy dissipation and deformation enhancement when the fault passes directly through the joints. Bellows joints in soft soil are better at dissipating energy, reducing pipe deformation, and mitigating pipe damage compared to those in hard soils. The internal pressure is helpful to increase the mechanical properties of the pipelines. The findings can provide some guidance for pipeline design and mitigation strategies for ensuring the reliability and safety of buried pipeline systems in earthquake-prone areas.

A Highly Sensitive 3D-Printed Flexible Sensor for Sensing Small Pressures in Deep-Sea High-Pressure Environment.

The origin of life on Earth is believed to be from the ocean, which offers abundant resources in its depths. However, deep-sea operations are limited due to the lack of underwater robots and rigid grippers with sensitive force sensors. Therefore, it is crucial for deep-sea pressure sensors to be integrated with mechanical hands for manipulation. Here, a flexible stress sensor is presented that can function effectively under high water pressure in the deep ocean. Inspired by biological structures found in the abyssal zone, our sensor is designed with an internal and external pressure balance structure (hollow interlocking spherical structure). The digital light processing (DLP) three-dimensional (3D) printing technology is utilized to construct this complex structure after obtaining optimized structural parameters using finite element simulation. The sensor exhibits linear sensitivity of 0.114 kPa-1 within the range of 0-15 kPa and has an extremely short response time of 32 ms, good dynamic-static load response capability, and excellent resistance cycling stability. It shows high sensitivity of 1.74 kPa-1 even under 30 MPa static water pressures and the theoretical working pressure can exceed 110 MPa, which provides a new solution for deep-sea robots.

Study of Ultra-High Performance Concrete Mechanical Behavior under High Temperatures.

The main concern with concrete at high temperatures is loss of strength and explosive spalling, which are more pronounced in high-strength concretes, such as Ultra-High Performance Concrete (UHPC). The use of polymeric fibers in the mixture helps control chipping, increasing porosity and reducing internal water vapor pressure, but their addition can impact its mechanical properties and workability. This study evaluated the physical and mechanical properties of UHPC with metallic and PVA fibers under high temperatures using a 23 central composite factorial design. The consistency of fresh UHPC and the compressive strength and elasticity modulus of hardened UHPC were measured. Above 300 °C, both compressive strength and elasticity modulus decreased drastically. Although the addition of PVA fibers reduced fluidity, it decreased the loss of compressive strength after exposure to high temperatures. The response surface indicates that the ideal mixture-1.65% steel fiber and 0.50% PVA fiber-achieved the highest compressive strength, both at room temperature and at high temperatures. However, PVA fibers did not protect UHPC against explosive spalling at the levels used in this research.

Effect of vent size on vented H2/N2/air deflagration

In this work, the coupling of explosion venting (vent size) and inerting (N2) on H2/air deflagration was investigated. Experiments were carried out in a vertical rectangular duct with an upper opening at an initial temperature and pressure of 280 K and 101 kPa, and a vent coefficient Kv was employed to replace the vent size to elucidate its effect on pressure buildup and flame propagation during H2/N2/air deflagration. In the present study, the internal pressure profile is monitored by three pressure sensors, PS1-3, which are installed at the bottom, center, and top of the duct, respectively, and the external pressure profile is obtained by PS4. The results show that the maximum internal overpressure (pmax) recorded by PS1-3 all increase with increasing Kv, but pmax obtained from PS2 and PS3 tend to increase linearly. For a given Kv, the maximum and minimum amplitudes of pmax are measured by PS1 and PS3, respectively. Specifically, the greater the distance between the pressure sensor and the upper opening, the greater the amplitude of pmax. The relationship between the maximum reduced explosion pressure (pred) and Kv is investigated, where pred is defined as the highest pmax for a specific Kv. As Kv increases from 2.2 to 11.9, pred increases from 26.25 kPa to 88 kPa. The maximum external flame velocity (Vext) increases from 83 m/s to 454 m/s with increasing Kv from 2.2 to 11.9. The amplitude of the maximum external overpressure (pext) first increases and decreases with an increase in Kv from 2.2 to 11.9. The formation time (Δt) of pext decreases and then increases and finally decreases with increasing Kv from 2.2 to 11.9. When Kv is increased from 2.2 to 4.1, all external fireballs are presented as mushroom shapes, but the external fireballs are gradually transformed into jet shapes for Kv ≥7.8. Two pressure oscillations, including Helmholtz oscillations and acoustic oscillations, are found. Acoustic oscillations are found in all tests, but Helmholtz oscillations are only observed for Kv ≤ 4.1.

Changes in magnetic characteristics of pipes during hydraulic and pneumatic tests of trunk pipelines

To identify the zones with the highest tensile stresses and deformations, a two-parameter magnetic method based on the measurement of coercive force and residual magnetic induction was applied. For realization of the method a mobile hardware and software complex DIUS-1.21M with an electromagnetic U-transducer was used, which was located along the pipe axis and along the pipe ring. Measurements were carried out on three pipes: in the first one magnetic characteristics were measured in the absence and under the influence of internal pressure; in the second and third ones — before the test and after the pipe fracture. It was revealed that internal pressure leads to the growth of residual magnetic induction in all zones both along the axis and along the ring, which indicates the occurrence of axial and circular tensile stresses in these zones, and the change of coercivity occurred ambiguously. It was found that fracture significantly increases the scatter of magnetic characteristics, which is explained by the complex nature of the stress-strain state of the fractured object.

Ultimate internal pressure bearing capacity of unconstrained and constrained X80 oil and gas pipelines with three typical dents

Three typical dents, denoted as types I, II, and III, encapsulate the prevailing manifestations of mechanical impairment encountered by oil and gas pipelines. Presently, scholarly attention is predominantly directed towards the scrutiny of load-bearing capabilities in pipelines afflicted by a solitary type of dent. To unravel the intricate impact of three typical dents on the performances of dented pipelines, three distinct models of pipeline dents under different constraints were studied in this work. These findings reveal that unconstrained dents consistently exhibit greater plastic strain and deformation zone dimensions compared to their constrained counterparts. The spring-back and rebound performances in unconstrained pipelines were fortified and the external load resistance in constrained pipelines was enhanced by augmenting the indenter diameter and introducing internal pressure. Both unconstrained dents and type I constrained dents failed consistently in the non-dented region, with their ultimate internal pressure resistance unaffected by the constraining factors. In contrast, type II and III constrained dents, featuring smaller indenters, greater dent depths, and reduced diameter-to-thickness ratios, failed within the dented region, which results in a weakened ultimate internal pressure-bearing capacity. Failure occurred in the non-dented region under opposite conditions, leaving the internal pressure resistance unaffected. Finally, dimensionless predictive formulas for the ultimate internal pressures of the type II constrained and type III X80 dented pipelines were obtained through nonlinear fitting. This comprehensive exploration revealed the variations in the ultimate internal pressure-bearing capacities induced by dents, thereby providing valuable insights for pipeline design and safety considerations.

Residual Strain and Joint Pressurization Maintain Collagen Tension for On-Joint Lumbar Facet Capsular Ligaments.

Modeling the lumbar facet capsular ligament's (FCL) mechanical behavior under various physiological motions has often been a challenge due to limited knowledge about the on-joint in situ ligament state arising from attachment to the bone or other internal loads. Building on prior work, this study presents an enhanced computational model of the lumbar facet capsular ligament by incorporating residual strain and joint pressurization strain, factors neglected in prior models. Further, the model can predict strain and stress distribution across the ligament under various spinal motions, highlighting the influence of the ligament's attachment to the bone, internal synovial fluid pressurization, and distribution of collagen fiber alignment on the overall mechanical response of the ligament. Joint space inflation was found to influence the total observed stress and strain fields, both at rest and during motion. A significant portion of the ligament was found to be in tension, even in the absence of external load. Additionally, the model's ability to account for residual strain offers a more realistic portrayal of the collagen fibers and elastin matrix's role in ligament mechanics. We conclude that (1) computational models of the lumbar facet capsular ligament should not assume that the ligament is unloaded when the joint is in its neutral position, and (2) the ligament is nearly always in tension, which may be important in terms of its long-term growth and remodeling.

Strain and stress responses of the springback and rerounding processes of dented pipelines

Denting, a common geometric defect in oil and gas pipelines, can threaten the structural integrity and safety of pipelines. A pipeline dent is usually caused by the collision or extrusion of hard objects during the pipeline construction and service stages. Some rebound occurs in the dented zone when the external load is removed. In actual engineering, unconstrained dents tend to reround with increasing internal pressure of the pipeline. This study experimentally and numerically investigated the processes of springback and rerounding of a dented pipeline. First, full-scale testing was carried out to simulate the springback and rerounding processes, and the strain variations at the dent were measured. Then, a 3-dimensional numerical model was developed and then validated against the experimental results. According to the experimental and numerical results, the stress and strain responses of the pipeline during the springback and rerounding processes were studied in detail. Furthermore, the factors influencing the springback and rerounding coefficients were discussed. Finally, equations for predicting the springback and rerounding coefficients of dented pipelines were proposed on the basis of a nonlinear regression analysis. The results show that mainly elastic recovery occurs during springback. After a dent is unloaded, the elastic strain and von Mises stress of the pipeline decrease greatly, while the plastic strain remains unchanged. The elastic strain increases with increasing internal pressure. The springback and rerounding coefficients increase with increasing indenter diameter and diameter-to-wall thickness, while the loading depth has a negative effect on these coefficients. The proposed formulas can be used as a reference for estimating the ratios of dent springback and rerounding of dented pipelines.

Mechanoresponsive regulation of myogenesis by the force-sensing transcriptional regulator Tono

Muscle morphogenesis is a multi-step program, starting with myoblast fusion, followed by myotube-tendon attachment and sarcomere assembly, with subsequent sarcomere maturation, mitochondrial amplification, and specialization. The correct chronological order of these steps requires precise control of the transcriptional regulators and their effectors. How this regulation is achieved during muscle development is not well understood. In a genome-wide RNAi screen in Drosophila, we identified the BTB-zinc-finger protein Tono (CG32121) as a muscle-specific transcriptional regulator. tono mutant flight muscles display severe deficits in mitochondria and sarcomere maturation, resulting in uncontrolled contractile forces causing muscle rupture and degeneration during development. Tono protein is expressed during sarcomere maturation and localizes in distinct condensates in flight muscle nuclei. Interestingly, internal pressure exerted by the maturing sarcomeres deforms the muscle nuclei into elongated shapes and changes the Tono condensates, suggesting that Tono senses the mechanical status of the muscle cells. Indeed, external mechanical pressure on the muscles triggers rapid liquid-liquid phase separation of Tono utilizing its BTB domain. Thus, we propose that Tono senses high mechanical pressure to adapt muscle transcription, specifically at the sarcomere maturation stages. Consistently, tono mutant muscles display specific defects in a transcriptional switch that represses early muscle differentiation genes and boosts late ones. We hypothesize that a similar mechano-responsive regulation mechanism may control the activity of related BTB-zinc-finger proteins that, if mutated, can result in uncontrolled force production in human muscle.

Studies on interactions of L-glutamic acid with L-arabinose/D-xylose in aqueous medium: Ultrasonic velocity and acoustic parameter studies supported by FTIR spectroscopic investigation

Glutamic acid is a non-essential amino acid, meaning that the body can synthesize it on its own, and it doesn’t necessarily need to be obtained from the diet. Using an ultrasonic interferometer, the ultrasonic velocity at 293.15 K and 298.15 K and at experimental pressure P = 101 kPa were determined in order to evaluate and comprehend the synergy between non-essential amino acid and saccharides (L-arabinose/D-xylose) in an aqueous system. There is a direct correlation between the weak and strong molecular interactions that occur between the solution’s constituents and the propagation of ultrasonic sound waves through the experimental solutions. Using the ultrasonic velocity data, isentropic compressibility (Ks) apparent molar isentropic compressibility (Ks,ϕ) and isothermal compressibility (KT) were calculated. In addition to these characteristics, acoustic impedance (Z), internal pressure (πi), relative association (RA), molar free volume (Vf), molar free length (Lf) and surface tension (γ) were deduced and analysed to advocates potent ion- solvent interactions. In order to gain understanding of Glu-Glu and Glu- L-arabinose/D-xylose interactions in aqueous medium, these parameters were interpreted. Ion-solvent interactions are stronger than ion-ion interactions due to the greater and positive values of Ks0. Strong contacts occur between the polar segments of L-arabinose/D-xylose and the zwitterionic groups of Glu, and these interactions become stronger as the concentration of L-arabinose/D-xylose increases, as indicated by positive values of Ks,ϕ,tr0. The water structure is reformed during the solvation and ion association processes of Glu. Furthermore, the spectroscopic investigation has been conducted using the FTIR technique in order to verify the results obtained from acoustic studies. Predominant ion-hydrophilic/hydrophobic interactions prevail in the studied system is validated by FTIR study. Absorption band widening indicates that intermolecular hydrogen bonding predominates over intramolecular hydrogen bonding.

An exact rigid/plastic solution for a thick-walled tube subject to internal pressure and axial load considering a general isotropic hardening law and its application

An exact rigid/plastic solution for a thick-walled tube subject to internal pressure and axial load considering a general isotropic hardening law and its application