Investigation of Snow Load Effects on Modal Parameters of a Steel Structure Roof

Snowfall is one of the environmental factors that can cause effects on the identification of structural modal parameters. For the steel structure roof of the Harbin Railway Station, effects of snow load to the modal parameters were investigated. A single-span simply supported beam was analysed from the theoretical perspective to study the principles. FEM-based analyses were conducted for the steel structure roof to illustrate the significance of the snow load effects to modal parameters. Uniformly and nonuniformly distributed snow loads were regarded as the essential factors influencing modal frequencies and mode shapes. Monitoring response data are collected and analysed to confirm the accuracy of analytical results. It is concluded that snowfall-induced variations on structural stiffness and mass matrices reduce the modal parameters and alter the mode shapes. The differences between the change regulations of the various modes are closely related to the distributions of snow loads. The theoretical and numerical analytical results are validated to be feasible and credible using temperature, axial strain, and acceleration measurements from the Harbin Railway Station field monitoring system

Analysis of the Deformation and Damage of Clamped Square Plates under Near-Field Explosion Loads

The deformation and damage mechanism of shell structures under near-field explosion loads has been of great significance in the theoretical study of impact dynamics and may serve as a dependable theoretic basis for the antiexplosion design of shell structures. In this paper, the plastic zone and crevasse size of clamped square plates under near-field explosion loads were discussed based on the plastic hinge law and energy theory. The crevasse size of a plate moving at motion modes Ι and ΙΙ under medium load was obtained according to the ultimate plastic strain criterion. Furthermore, the plastic zone under a high load was determined in terms of the movement law of a plastic hinge line. When the applied load ended, the crevasse sizes of the plates at motion modes III and IV were deduced on the basis of the principle of energy conservation. Finally, numerical simulation was used to analyse the deformation and damage mechanism of the shell structures under near-field explosion loads. The theory and method proposed in this paper are verified using ANSYS software and compared with the experimental results. This study verifies the validity of the proposed approach for analysis of the deformation and damage of a clamped square plate under near-field explosion loads

A New Co-Crystal of Synthetic Drug Rosiglitazone with Natural Medicine Berberine: Preparation, Crystal Structures, and Dissolution

A co-crystal of rosiglitazone (Rsg) with berberine (Bbr), Rsg-Bbr, was prepared by the solvent evaporation method and characterized. The results showed that the electrostatic attraction existed between the nitrogen anion of rosiglitazone and the quaternary ammonium cation of berberine, and C-H···O hydrogen bonds were formed between Rsg and Bbr. In the crystal structure, rosiglitazone molecules stack into a supramolecular layer through π-π interactions while π-π interactions between berberine cations also result in a similar layer. The co-crystal presented a low moisture adsorption curve in the range of 0−95% relative humidity values at 25 °C. The improved dissolution rate of rosiglitazone in pH = 6.8 buffer solution could be achieved after forming co-crystal

Multicomponent Crystal of Metformin and Barbital: Design, Crystal Structure Analysis and Characterization

The formation of most multicomponent crystals relies on the interaction of hydrogen bonds between the components, so rational crystal design based on the expected hydrogen-bonded supramolecular synthons was employed to establish supramolecular compounds with desirable properties. This theory was put into practice for metformin to participate in more therapeutic fields to search for a fast and simple approach for the screening of candidate crystal co-formers. The prediction of intermolecular synthons facilitated the successful synthesis of a new multicomponent crystal of metformin (Met) and barbital (Bar) through an anion exchange reaction and cooling crystallization method. The single crystal X-ray diffraction analysis demonstrated the hydrogen bond-based ureide/ureide and guanidine/ureide synthons were responsible for the self-assembly of the primary structural motif and extended into infinite supramolecular heterocatemeric structures

A Glimepiride-Metformin Multidrug Crystal: Synthesis, Crystal Structure Analysis, and Physicochemical Properties

A multidrug crystal based on drug combinations was synthesized by the solvent evaporation method. This multicomponent crystal consisted of antidiabetic drugs Glimepiride (Gli) and Metformin (Met), which was performed by single crystal X-ray structure analysis. The results showed an enhancement of the pharmaceutical properties such as lower hygroscopicity and greater accelerated stability than the parent drug Met, and a higher solubility and dissolution rate than Gli

Improving Dissolution and Cytotoxicity by Forming Multidrug Crystals

Both rosiglitazone and metformin have effects on blood glucose regulation and the proliferation of liver cancer cells. Combination therapy with these two drugs is common and effective for the treatment of diabetes in the clinic, however, the application of these two drugs is influenced by the poor dissolution of rosiglitazone and the gastrointestinal side-effect of metformin resulting from a high solubility. The formation of a multidrug crystal form (Rsg-Met) by a solvent evaporation method can solve the solubility issue. Crystal structure data and intramolecular hydrogen bonds were detected by X-ray diffraction and infrared spectroscopy. Surprisingly, Rsg-Met shortens the time spent in solubility equilibrium and multiplies the dissolution rate of Rsg. Finally, we found that a low concentration of Rsg-Met enhanced the proliferation inhibition effect on liver cancer cells (HepG2, SK-hep1) compared with rosiglitazone, without affecting the human normal cell line LO2

Immobilizing Water into Crystal Lattice of Calcium Sulfate for its Separation from Water-in-Oil Emulsion

This work report a facile approach to efficiently separate surfactant-stabilized water (droplet diameter of around 2.0 μm) from water-in-oil emulsion via converting liquid water into solid crystal water followed by removal with centrifugation. The liquid–solid conversion is achieved through the solid-to-solid phase transition of calcium sulfate hemihydrate (CaSO₄. 0.5H₂O, HH) to dihydrate (CaSO₄·2H₂O, DH), which could immobilize the water into crystal lattice of DH. For emulsion of 10 mg mL^–1 water, the immobilization-separation process using polycrystalline HH nanoellipsoids could remove 95.87 wt % water at room temperature. The separation efficiency can be further improved to 99.85 wt % by optimizing the HH dosage, temperature, HH size and crystalline structure. Property examination of the recycled oil confirms that our method has neglectable side-effect on oil quality. The byproduct DH was recycled to alpha-HH (a valuable cemetitious material widely used in construction and binding field), which minimizes the risk of secondary pollution and promotes the practicality of our method. With the high separation efficiency, the “green” feature and the recyclability of DH byproduct, the HH-based immobilization-separation approach is highly promising in purifying oil with undesired water contamination