A modeling concept of a mechanical system having a piecewise linear spring property for its diagnosis

Machine condition monitoring and fault diagnosis of rotating machinery are very important because of the wide use of rotating machinery in industry. Couplings and gears are used in many mechanical systems to connect elements and transmit power. The system is usually modeled as a single-degree-of-freedom system with a piecewise linear spring property, where the mass of main machine is only considered. In the present study, the dynamic behavior of a system with an unsymmetrical nonlinearity and a significant mass of the connecting part was investigated both experimentally and by numerical simulation. In the experiment, a 1/3 sub-harmonic oscillation was observed, but this oscillation was not found in the simulation using a single-degree-of-freedom system, in which the mass of the connecting part was ignored. However, when a two-degrees-of-freedom system was used that considered both the mass of the connecting part and the impact property, the 1/3 sub-harmonic oscillation was observed. Thus it is recognized that an adequate mathematical model for diagnosis in the early stage of abnormality must be selected on the basis of the mass ratio between the connecting part and the main body.     

Molecular deformation mechanisms of isotactic polypropylene in α‐ and β‐crystal forms by FTIR spectroscopy

The orientation behavior of isotactic polypropylene (iPP) in α‐ and β‐crystal form was investigated by rheo‐optical Fourier transformed infrared (FTIR) spectroscopy. This method enabled quantification of the degree of orientation as a feature of structural changes during uniaxial elongation in not only the crystalline phase but also the amorphous one. Molecular orientation mechanisms can be successfully derived from experimental results. Generally, three mechanisms were detected for iPP: (1) interlamellar separation in the amorphous phase, (2) interlamellar slip and lamellar twisting at small elongations, and (3) intralamellar slip at high elongations. The third mechanism was favored by α‐PP, whereas β‐PP favored the second mechanism, which, in fact, was responsible for the different mechanical properties of both materials at the macroscopic level. On the other hand, crystallization conditions may have significantly affected the amorphous orientation. Nevertheless, for both iPP types the chains in the amorphous phase always oriented less than did those in the crystalline phase. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4478–4488, 2004     

Diethyl 1-(p-fluoro­phenyl)-5-oxo-3-(2-thienyl)­pyrrolidine-2,2-di­carboxyl­ate

In the title compound, C₂₀H₂₀FNO₅S, the pyrrolidine ring adopts an envelope conformation. The fluoro­phenyl and thio­phene rings are individually planar. The molecular and crystal structures are stabilized by intra- and intermolecular C—H⋯O interactions.     

Oxidation reactions of 1,3-diphenylpropane-1,3-dione

The free radical scavenging properties and possible antioxidant activity of 1,3-diphenylpropane-1,3-dione (1) are reported. Pulse radiolysis technique was employed to study the one-electron oxidation of 1 with various radicals viz. CCl₃O₂ ^•, N₃ ^• and^•OH in homogeneous aqueous solution. All these radicals reacted with 1 under ambient conditions at almost diffusion controlled rates producing transient species with an absorption maximum around 420 nm that decayed at first order rates. The transient absorption peak was shifted in the case of CCl₃OO^• radical reaction with 1 due to change in the polarity of the medium. Formation of a stable product with a broad absorption band starting from 400 nm and cut off at 230 nm was observed in the oxidation of 1 with^•OH and^•N₃ radicals. In a biological system also, 1 showed significant inhibitory activity against Fe²⁺-mediatedlipidperoxidation. Based on these observations, a suitable mechanism for the oxidation of 1 has been proposed.     

Structure and Conformation of Individual Molecules upon Adsorption of a Mixture of Benzoporphyrins on Ag(111), Cu(111), and Cu(110) Surfaces

The front cover artwork is provided by the groups of Prof. Dr. Hans-Peter Steinrück and Prof. Dr. Norbert Jux at the Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg. The image shows a mixture of six 2H-tetrakis-(3, 5-di-tert-butyl-phenyl)(x)benzoporphyrins (2H-diTTBP(x)BPs, x = 0, 1, 2-cis, 2-trans, 3, or 4) molecules forming a porous square structure on Ag(111) as observed in scanning tunneling microscopy (STM) at room temperature. Read the full text of the Research Article at 10.1002/cphc.202300355 .     

Effect of artificial mucus properties on the characteristics of airborne bioaerosol droplets generated during simulated coughing

The effect of viscoelastic properties and surface tension of artificial mucus simulant samples on the size distribution and volume concentration of bioaerosol droplets generated during simulated coughing was investigated through in vitro experiments. The mucus simulant samples had viscoelastic properties in a similar range as those of real human airway mucus. The mucus simulant gels were prepared by mixing various proportions of 0.5–1.7% locust bean gum solution and 0.1 M sodium tetraborate (XLB) solution. Surface tension of one set of samples was varied by adding different amounts of SDS (sodium dodecyl sulfate) surfactant while the measurement of surface tension was performed using ADSA (axisymmetric drop shape analysis) method. The viscoelastic properties of the samples were measured using a Bohlin Gemini 200 HR (Malvern, UK) nano-rheometer with peltier plate assembly. An artificial cough machine was used to simulate human cough, generating aerosol droplets in a model trachea attached to the front of the cough machine. The size distribution and volume concentration of the droplets generated through simulated cough were measured using a laser diffraction particle sizer (SprayTec, Malvern, USA). The surface tension was found to have negligible effect on the characteristic of generated droplets within the range of this investigation. The experimental results showed a decrease in particle size as the samples changed from a viscous fluid type to a viscoelastic to an elastic solid type sample. The volume concentration also changed significantly as the viscoelasticity of the samples was varied.