Bent Structure Research Articles

Seismic fragility assessment of aqueduct bent structures subjected to mainshock-aftershock sequences

This study aims to assess the seismic fragility of the aqueduct bent structure subjected to mainshock-aftershock (MS-AS) ground motion sequences by double incremental dynamic analysis method. The finite element model of the aqueduct bent structure is developed in OpenSees platform and numerical simulation technique is validated through physical test results. A series of nonlinear dynamic time-history analysis is carried out on the aqueduct bent structure to obtain its seismic response under different ground motion intensities. Furthermore, the incremental dynamic analysis (IDA) data cluster and median lines of the damage measure of the aqueduct bent structure are constructed. The advanced probabilistic seismic demand model (PSDM) of the aqueduct bent structure subjected to MS-AS ground motion sequences is proposed. Based on the proposed PSDM and the predefined damage states, the fragility surfaces of the aqueduct bent structure are also developed by adopting the vector-valued intensity measures considering the mainshock intensities (IMm) and aftershock intensities (IMa). Meanwhile, for the sake of comparation, the aftershock fragility curves of the aqueduct bent structure under different mainshock intensities are drawn, which emphasizes the importance of aftershocks in the seismic risk assessment. The analysis results indicate that the proposed piecewise probabilistic seismic demand model can better fit the logarithmic relationship between the aftershock intensities and the median of the reinforcement longitudinal tensile strain. The structural fragility probability increase with the increase of mainshock and aftershock intensities. It turns out that the mainshock intensities play a leading role in the damage probability of the aqueduct structure subjected to MS-AS ground motion sequences, the aftershock can cause additional damage to the aqueduct bent structure and reduce its seismic capacity. The meaningful results can provide supports for seismic optimization design, resilience improvement and post-earthquake repair-demand of the aqueduct structure in Southwest China.

Experimental study on 3D printed heat pipes with hybrid screen–groove combined capillary wick structure

The integration of heat pipes as a passive thermal management system for nuclear reactors has been proposed as it provides the advantages of compact design, reliability, efficient heat transfer performance, and enhanced safety. Applying the heat pipe to a nuclear reactor without collision between systems and achieving efficient long-distance heat transfer requires the manufacturing of heat pipes with a high degree of freedom. Using three-dimensional (3D)-printing technology can be a solution for fabricating complex or bent capillary wick heat pipes into an integrated geometry. The study involves the production of a heat pipe using metal 3D-printing technology and an experimental study conducted for thermal performance evaluation. The heat pipe includes a combination of a screen-groove wick in the evaporator section, a groove wick in the adiabatic and condenser sections, and a bent wick structure in the middle. By using 3D printing technology, it is possible to create a heat pipe that has a complex wick design, a consistent porous structure and remains undistorted during the manufacturing process. The surface roughness of the 3D-printed heat pipe was 17 to 1700 times higher than the commercial stainless-steel pipe, which has the benefit for enhance capillary performance. The experimental results showed that the 3D-printed heat pipe can achieve high effective thermal conductivity up to 25.7 kW/m-K and showed 24.2% lower thermal resistance compared to the conventionally manufactured heat pipe. Furthermore, it can be successfully operated at various inclination angles.

Total Synthesis and Structural Studies of Zwitterionic Bacteroides fragilis Polysaccharide A1 Fragments.

Zwitterionic polysaccharides (ZPSs) are exceptional carbohydrates, carrying both positively charged amine groups and negatively charged carboxylates, that can be loaded onto MHC-II molecules to activate T cells. It remains enigmatic, however, how these polysaccharides bind to these receptors, and to understand the structural features responsible for this "peptide-like" behavior, well-defined ZPS fragments are required in sufficient quantity and quality. We here present the first total synthesis of Bacteroides fragilis PS A1 fragments encompassing up to 12 monosaccharides, representing three repeating units. Key to our successful syntheses has been the incorporation of a C-3,C-6-silylidene-bridged "ring-inverted" galactosamine building block that was designed to act as an apt nucleophile as well as a stereoselective glycosyl donor. Our stereoselective synthesis route is further characterized by a unique protecting group strategy, built on base-labile protecting groups, which has allowed the incorporation of an orthogonal alkyne functionalization handle. Detailed structural studies have revealed that the assembled oligosaccharides take up a bent structure, which translates into a left-handed helix for larger PS A1 polysaccharides, presenting the key positively charged amino groups to the outside of the helix. The availability of the fragments and the insight into their secondary structure will enable detailed interaction studies with binding proteins to unravel the mode of action of these unique oligosaccharides at the atomic level.

Seismic performance analysis of orthotropic shear walls based on the deformation energy decomposition method

Based on orthogonal completeness and mechanical equilibrium, the physical parameters of materials are further considered, and the deformation decomposition method is improved and applied to orthotropic structures. The method is realized by compiling ANSYS-MATLAB computer algorithms, and verified by strain energy analysis and experimental results. It not only quantitatively identifies tensile, compressive, bending and shear deformation energies of orthotropic structures, but also visualizes the regions dominated by the aforementioned fundamental deformation energies. Furthermore, the influence of the horizontal and vertical elastic modulus ratios of coupling beams and wall-columns on the seismic performance of orthotropic shear walls with different opening sizes is discussed. The results show that the ductility of the coupling beam and the wall-column is improved by appropriately reducing the horizontal and vertical elastic modulus ratio of the coupling beam, and the effect on the wall-column is weakened with the reduction of the opening size. But the lateral resistance of the shear wall is weakened. The wall-column ductility is improved by properly increasing the horizontal and vertical elastic modulus ratio of the wall-column, but the lateral resistance of the shear wall is weakened.

Interaction between a photoisomerizable azobenzene compound and alpha-lactalbumin: Spectroscopic and computational simulation studies

The combination of light and photoresponsive compounds provides a peculiar way of regulating biological systems. Azobenzene is a classical organic compound with photoisomerization properties. Exploring the interactions between azobenzene and proteins can deepen the biochemical applications of the azobenzene compounds. In this paper, the interaction of 4-[(2,6-dimethylphenyl)diazenyl]-3,5-dimethylphenol with alpha-lactalbumin was investigated by UV–Vis absorption spectra, multiple fluorescence spectra, computer simulations, and circular dichroism spectra. Most critically, the interaction differences between proteins and the trans- and cis-isomer of ligands have been analyzed and compared. Results showed that both isomers of ligands were bound to alpha-lactalbumin to form ground state complexes and statically quenched the steady-state fluorescence of alpha-lactalbumin. The van der Waals forces and hydrogen bonding dominated the binding; the difference is that the binding of the cis-isomer to alpha-lactalbumin is more rapidly stabilized, and the binding strength is greater than the trans-isomer. These binding differences were modeled and analyzed by molecular docking and kinetic simulations, and we found that both isomers bind through the hydrophobic aromatic cluster 2 of alpha-lactalbumin. However, the bent structure of the cis-isomer is more closely aligned with the construction of the aromatic cluster and may have contributed to the above differences.

Numerical analysis of pyrolysis and coking of aviation kerosene in a rectangular U-bend tube under one-side heating

Pyrolysis and coking of Chinese aviation kerosene RP-3 in a rectangular U-bend tube of nonuniformly heating was numerically simulated. Discussion was held regarding how the bending structure affected temperature distribution, thermal cracking, and pyrolytic deposition. Results indicated that the secondary flow induced by centrifugal forces effectively promoted thermal convection between near-wall and core regions. This effect further decreased the fuel temperature of near-wall region. Furthermore, nonuniform distribution of temperature in the U-bend tube was reduced. More RP-3 reacted along the heated wall in the straight tube, which significantly accelerated the average reaction rate in the cross section and increased the yield of coke precursors formed by secondary reactions. Notably, the curved structure promoted heat transfer and anticoke deposition performance. Under the same inner surface area, the total amount of pyrolytic deposition of U-bend tube was reduced by 17.77 mg during coking duration of 5 min.

Mechanical properties of structured copper and printed silver hybrid stretchable electronic systems

Stretchable electronics can be realized using different manufacturing methods and hybrids thereof. An example of the latter is the combination of stretchable circuit boards with screen-printing, which will be discussed in this work. The hybrid stretchable electronics structures are based on photolithographically structured and rigid copper islands and screen-printed silver ink interconnections. This enables the assembly of components with a high number of contacts onto the copper islands and deformable silver ink lines between islands. The transition area between islands and lines is critical due to local stress concentration. The effect and potential mitigations were studied by measuring the electrical resistance of test interconnections under mechanical loading. The first set of samples was elongated up to 30% in tensile tests. The second set of samples was elongated 10%, 20%, and 30% in cyclic tests up to 10 000 cycles. After the tests, extensive failure analysis, e.g. scanning electron microscope, and finite element analysis were conducted. In tensile tests at maximum load, the interconnections either snap apart or their resistance increases by 640% in the transition area. Adding protective structures around the transition area, the resistance increase can be reduced to 12%. Stress concentration in the transition area can be controlled with the layout of the structures, as shown in the cyclic tests. Depending on a layout, the structures protect interconnections in the transition area (resistance <4 Ω at 10% and 20% throughout 10 000 cycles, and up to 5000 cycles at 30% elongation), or with particular designs, cause fatal damage of the circuitry and fail early. The identified failure mechanism is typically fatigue damage caused by the repeated bending of the protective structure. The observed resistance increase at the interface was closely related to the crack propagation phase in the protective structures.

Toward new liquid crystal phases of DNA mesogens

Short, partially complementary, single-stranded (ss)DNA strands can form nanostructures with a wide variety of shapes and mechanical properties. It is well known that semiflexible, linear dsDNA can undergo an isotropic to nematic (IN) phase transition and that sufficiently bent structures can form a biaxial nematic phase. Here, we use numerical simulations to explore how the phase behavior of linear DNA constructs changes as we tune the mechanical properties of the constituent DNA by changing the nucleotide sequence. The IN-phase transition can be suppressed in so-called DNA “nunchakus”: structures consisting of two rigid dsDNA arms, separated by a sufficiently flexible spacer. In this paper, we use simulations to explore what phase behavior to expect for different linear DNA constructs. To this end, we first performed numerical simulations exploring the structural properties of a number of different DNA oligonucleotides using the oxDNA package. We then used the structural information generated in the oxDNA simulations to construct more coarse-grained models of the rod-like, bent-core, and nunchaku DNA. These coarse-grained models were used to explore the phase behavior of suspensions of the various DNA constructs. The approach explored in this paper makes it possible to “design” the phase behavior of DNA constructs by a suitable choice of the constituent nucleotide sequence.

Comparative Study on Design &amp; Analysis of Multi-Storied Building and Mono-Column Building

Abstract: The comparative study on analysis of RCC Frame structure supported on a mono-column and multi-column is done in this paper. Economic comparisons, Land space comparison is done between RCC mono-column and RCC multi-column structure. This project presents structural modelling, stress, bending moment, shear force and displacement, deflection design considerations for a structure and it is analysed by using STAAD-Pro software. Various steps concerned in designing of RCC Frame structure supported on a mono-column and multi-column by using STAAD-Pro software are Geometric Modelling, providing material properties and sectional Properties, fixing supports and boundary conditions, providing loads &amp; load combinations, Special Commands, Analysis Specification , Design Command and report.

Comparative rotatory power of bent and twisted polyynes.

Linear polyynes of the formula C18 H2 (symmetry D∞h ) were bent in silico by progressively introducing CCC angles less than 180°. The bent structures (symmetry C2v ) were then twisted by introducing torsion angles across the CCCC segments by as much as 60°. The gyration tensors of these 19 structures (linear, bent, and twisted) were computed by linear response methods. Bending is massively generative of optical activity in oriented structures, even achiral structures, whereas twisting in conjunction with bending, serves to linearize the molecules and diminish maximally observable optical activity. This computational exercise is intended to unbind the infelicitous linkage of optical activity and chirality, which is only meaningful in isotropic media. Although bent structures are not optically active in solution-the spatial average of the optical activity is necessarily zero-solution measurements that deliver the spatial averages are a special class of measurements, albeit the overwhelmingly most common chiroptical measurements, that prejudice our common understanding of how π-conjugated structures generate gyration. Bending is far more effective than twisting at generating optical activity along some directions for oriented structures. The respective contributions from the transition electric dipole-magnetic dipole polarizability and the transition electric dipole-electric quadrupole polarizability are compared.

Researches Advanced in Intubation Based on SLAM

Intubation is an emergency medical procedure used to rescue people who are unconscious or unable to breathe on their own. In the process of tracheal intubation, traditional intubation is difficult due to narrow viewing angle, trachea bending, and occlusion of internal structures. Thanks to the rapid development of simultaneous localization and mapping (SLAM) and virtual reality (AR) technologies, intubation aids are also developing towards intelligence and automation. Based on the collection and analysis of a large number of literatures, this paper conducts an in-depth study of the existing SLAM-based intubation-assisted technology. Specifically, on the basis of analyzing the current research on the application of equipment, visualization schemes, and algorithm schemes in tracheal intubation and intubation training, this paper studies the application progress in terms of efficiency, versatility, accuracy, and user feedback. Further, we summarize the existing key issues and discuss future developments.

Analysis of the Mechanical Properties and Study of Influential Factors of Different Materials in Tape Spring

This paper analyzes and calculates the mechanical properties of composite tape spring structures during folding and bending and establishes a non-linear control equation for the folding and bending of composite laminate tape spring structures. Accurate expressions for folding and bending displacements are obtained. The influence of the cross-section’s central angle and the composite tape spring’s ply thickness on their mechanical properties are analyzed. Finite element numerical analysis is performed on [−45 45]s laminated composite tape springs, and the correctness of the theoretical derivation is proved by comparing the curvature radius-bending moment curve. Based on previous research, the mechanical properties of different tape spring materials and structures are compared, further studying the lightweight design of space deployment mechanisms. The results show that the steady-state bending moment performance of composite tape springs is excellent, with a 162.1% improvement in steady-state bending moment performance per unit mass compared to traditional metallic tape springs. Additionally, the critical bending moment performance of negative Poisson ratio honeycomb structure tape springs is also excellent, with a 62.3% improvement in steady-state bending moment performance per unit mass compared to traditional metallic tape springs.

Experimental, Grand canonical Monte Carlo, and Density Functional Theory studies for comparing halloysite and kaolinite on heavy metals fate during pyrolysis of solid waste

In this study, we utilized low-cost halloysite (Hal) for the first time to enhance the solid-phase enrichment and stability of heavy metals (HMs) during solid waste pyrolysis through experimental and theoretical methods, and compared with kaolinite (Kao). Experimental results demonstrated that Hal was superior to Kao in improving the solid-phase enrichment of HMs. Specifically, the solid-phase enrichment of Cd increased by 32.6 % (500 °C) and 25.94 % (600 °C), while that of Pb and Zn increased by 17.37 %/16.83 % and 19.82 %/22.37 % (700/800 °C), respectively. Adding Hal reduced the proportion of HMs in the unstable fraction (F1 + F2), consequently lowering the environmental risk of biochar and the extractable state of HMs. Through Grand canonical Monte Carlo and Density Functional Theory (DFT) simulations, we analyzed the adsorption amounts, adsorption sites, and adsorption mechanisms of Cd/Pb compound on Hal/Kao surfaces, revealing that the primary factor influencing the adsorption performance of Hal and Kao was the difference in specific surface area. The adsorption amounts of HMs by Hal were significantly higher than Kao and decreased with increasing temperature, while the difference in adsorption performance caused by structural bending was negligible. The DFT results indicated that Cd and Pb monomers were stabilized by establishing covalent bonds with OH or reactive O atoms on the Al-(001) surface, whereas the covalent bonds with ionic bonding properties formed between Cl atoms and unsaturated Al atoms played a crucial role in stabilizing HM chlorides. Furthermore, the adsorption energy of Hal on HMs increased with the removal rate of OH. Our study highlights the potential of Hal in stabilizing HMs during pyrolysis without requiring any modifications, thereby avoiding the generation of modified waste solutions and unnecessary cost loss.

Comparison of Outcome of three Different Approaches for Supracondylar Humerus Fractures in Children

Introduction Supracondylar humerus is one of the most common elbow fractures in children. It accounts for about 60% of all the elbow fracture. It is a challenging orthopedic presentation. It is more common in the children younger than 15. The bending structure and weak metamorphic sclerotin of distal humerus are the underlying cause behind these fractures. Fractures are classified according to the Gartland’s criteria. Study design: It is a retrospective study conducted at Sahara Medical College, Narowal and Pakistan Railway General Hospital, Rawalpindi for duration of six months from August 2022 to January 2023. Material and Methods: The patients were aware of the study objective. The demographic features of each selected patient were recorded. There were total 150 patients included in this study. Patients were divided into three groups on the basis of type of approach used for the treatment of supracondylar humerus fracture; lateral approach, medial approach and posterior approach as group A, B and C respectively. Results: The average age of patients was 7.61±4.5, 7.2±3.6 and 6.5±4.5 years for group A, B and C respectively. The reason of fracture was determined and the data revealed that most of the injuries were related to sports. P value was calculated and the data was statistically significant. Conclusion: Our results suggest that as compared to posterior and medial, lateral approach is better as it showed significant radiological and functional outcomes. It can be used by surgeons as it takes less time and the complications rate is lower. Keywords: lateral approach, supracondylar humerus and posterior approach.

Experimental study of installing a dune model in a 90° bend of the horizontal-vertical pneumatic conveying system based on wavelet multi-resolution analysis

In the pneumatic conveying process, the particles move to the bend under the influence of inertia to form a particle rope, which will cause a serious collision between the pipe wall and the particles. In order to reduce energy consumption, three sizes of dune models were designed according to the bend structure and blockage ratio. The system pressure drops, particle flow pattern, particle velocity distribution, and pulsation velocity intensity are studied in this research, and the wavelet multi-resolution analysis is used to perform the particle velocity. The findings indicate that the dune model effectively reduces the ideal conveying gas velocity and pressure drop, and the maximum reduction rate of ideal conveying gas velocity is 10.26%. The dispersion of particles is fully in the vertical pipe in the condition of dune model and the axial velocity is larger than the condition of no model. Moreover, the large-scale low-frequency motion dominates the movement of particles in the pipe, while the appearance of small-scale high-frequency motion breaks the pattern of low-frequency motion.

Deconvolution approach for floating wind turbines

AbstractGreen renewable energy is produced by floating offshore wind turbines (FOWT), a crucial component of the modern offshore wind energy industry. It is a safety concern to accurately evaluate excessive weights while the FOWT operates in adverse weather conditions. Under certain water conditions, dangerous structural bending moments may result in operational concerns. Using commercial FAST software, the study's hydrodynamic ambient wave loads were calculated and converted into FOWT structural loads. This article suggests a Monte Carlo‐based engineering technique that, depending on simulations or observations, is computationally effective for predicting extreme statistics of either the load or the response process. The innovative deconvolution technique has been thoroughly explained. The suggested approach effectively uses the entire set of data to produce a clear but accurate estimate for severe response values and fatigue life. In this study, estimated extreme values obtained using a novel deconvolution approach were compared to identical values produced using the modified Weibull technique. It is expected that the enhanced new de‐convolution methodology may offer a dependable and correct forecast of severe structural loads based on the overall performance of the advised de‐convolution approach due to environmental wave loading.

Occurrence Modes of Critical Metals (Li+ and Ge4+) in the Organic Molecular Structures of Coal: A Density Functional Theory Study.

To explore the mechanism of critical metal (Li+ and Ge4+) occurrence in the organic molecular structures of different rank coals, simulations were investigated using quantum chemical density functional theory. In this paper, Wender lignite, bituminous, and anthracite molecular models were used as organic molecular structures in coal. The electrostatic potential (ESP), frontier molecular orbitals, and Mulliken charges were used to identify adsorption sites in organic molecular structures. Mulliken charge, bond length, Mayer bond order (MBO), and adsorption energy values were used to estimate the binding conformation and strength between organic molecular structures and critical metals (Li+ and Ge4+). The results showed that the negative ESP, the highest occupied molecular orbitals, and negative Mulliken charges in the organic molecular structures were located at the O atom of oxygen functional groups and the aromatic structures, respectively, which were the active sites for critical metal adsorption. Mulliken charge transfer, bond length, MBO, and adsorption energy data suggested that the binding of Li+ with organic molecular structures was controlled by the carbonyl group (C=O), while the aromatic structures had less effect on the occurrence of Li+ in the organic molecular structures. The maximum adsorption energy value for binding Li+ with organic molecular structures was -742.16 kJ/mol. The Ge4+ ions not only showed strong binding ability with oxygen functional groups, but also Ge4+ formed thermodynamically stable half-sandwich complexes with aromatic structures. Therefore, the coal rank had little effect on the binding of Ge4+ with organic molecular structures. Moreover, the binding of Ge4+ with organic molecule structures was enhanced by the synergistic interactions of oxygen functional groups and aromatic structures. The adsorption energy values were up to -8511.43 kJ/mol. The adsorption of organic matter in coal to critical metals (Li+ and Ge4+) generated changes in the spatial configuration of the organic molecular structure, including local twisting of the organic molecular structure in lignite and bending of the aromatic structure in anthracite.

Free-form optimization of pattern shape for improving mechanical characteristics of a concentric tube

Medical concentric tubes have recently been designed using auxetic structures with negative Poisson's ratios to reduce undesirable snapping instability and improve mechanical performance. Despite the vast range of stiffness levels, prior auxetic designs were restricted to relatively simple geometries like square or triangular holes. Here, we present a novel free-form optimization for designing the bending and torsional stiffness of tubular structures using the multi-objective Bayesian optimization (MBO) method. The initial dataset of hole shapes is generated using a non-parametric Bézier curve, and the corresponding mechanical properties are estimated via numerical analysis. The acquisition function suggests a new hole shape with higher performance metrics based on the dataset, and updates to the regression model are made with new data points to improve prediction accuracy. Compared to a conventional tube with rectangular holes, the optimized design improves key factor, a ratio of bending stiffness to torsional rigidity, and torsional stiffness by 32% and 25%, respectively, by expanding the existing design space. The performance of the optimally designed tube was validated by resonant vibration tests.

Integrated analysis of soil-structure interaction for statically indeterminate beams on spatially random soils

ABSTRACT This study aimed to develop an integrated approach to analyse the interaction between soils and beams. The research methods involved placing a statically indeterminate beam on spatially random soils, where soil springs acted as supports for the beam. The soil spring stiffness values were simulated using random field theory. This integrated approach was embedded in the Monte Carlo simulation framework to facilitate probabilistic assessment. This study concluded that the force method solution accurately determined the bending moment and shear diagrams for a beam supported by soil springs. Additionally, soil spatial variability had a significant impact on the beam responses, including the variations in footing settlements, support reactions, bending moment, and shear force. This study also identified a critical scale of soil fluctuation that coincides with the beam span, which resulted in the highest probability of structural bending failure. Overall, this study highlights the importance of accounting for soil spatial variability in an integrated geotechnical and structural design approach.

Signature of spin-triplet exciton condensations in LaCoO3 at ultrahigh magnetic fields up to 600 T

Bose-Einstein condensation of electron-hole pairs, exciton condensation, has been effortfully investigated since predicted 60 years ago. Irrefutable evidence has still been lacking due to experimental difficulties in verifying the condensation of the charge neutral and non-magnetic spin-singlet excitons. Whilst, condensation of spin-triplet excitons is a promising frontier because spin supercurrent and spin-Seebeck effects will be observable. A canonical cobaltite LaCoO3 under very high magnetic fields is a propitious candidate, yet to be verified. Here, we unveil the exotic phase diagram of LaCoO3 up to 600 T generated using the electromagnetic flux compression method and the state-of-the-art magnetostriction gauge. We found the continuous magnetostriction curves and a bending structure, which suggest the emergence of two distinct spin-triplet exciton condensates. By constructing a phenomenological model, we showed that quantum fluctuations of excitons are crucial for the field-induced successive transitions. The spin-triplet exciton condensation in a cobaltite, which is three-dimensional and thermally equilibrated, opens up a novel venue for spintronics technologies with spin-supercurrent such as a spin Josephson junction.