Visualisation of barely visible impact damage in polymer matrix composites using an optical deformation and strain measurement system (ODSMS)

This study deals with damage evaluation using an Optical Deformation and Strain Measurement System (ODSMS). Damage was introduced using an Instrumented Falling Weight Impact Test (IFWIT) machine. The incident impact energy was controlled to low magnitude so that the specimen was not penetrated and only internal or barely visible damage was introduced. This damage can have an adverse effect on structural integrity, and potentially lead to catastrophic failure. It is important to identify the damage and assess the structural integrity of components made of composites non-destructively. This paper presents the theoretical aspects involved in ODSMS and its capability of evaluating the impact induced internal damage. It has been found that ODSMS can successfully identify the internal damage in terms the strain concentrations at different loading levels. The damage location and geometrical characteristics are in good agreement with those evaluated by conventional NDT techniques.     

Temperature changes of the optical properties of (SiO2) n , (GaAs) m , and (SiO2) n (GaAs) m nanoparticles: Computer experiment

The optical properties of silicon dioxide and gallium arsenide nanoparticles and the four-component particles based on them were calculated by the molecular dynamics method. The complex dielectric permittivity, infrared and Raman spectra, refractive index, and absorption coefficient of these nano particles were determined. The temperature dependences of the infrared and Raman spectra and the number of the optically active electrons in the nanoparticles composed of a semiconductor and/or a dielectric were investigated.     

The periodic system: The (multiple) values of an icon

The periodic system is an icon of science, with an exceptional level of usage around the world. It is especially celebrated as a source of information and pedagogical tool. Although many publications on the history and philosophy of the system have appeared over the years, few of them deal with its underlying values aside from predictability. In this issue, scholars from different disciplines use the history of the periodic system to discuss what the system signifies and has signified for scientists and teachers, as well as for philosophers and historians. By presenting different layers of underlying values as they appear in the eyes of the users, we aim to provide a richer understanding of the periodic system, past and present.     

AlGaAs/GaAs-heterostructure cw laser diodes with a working output optical power of 3 W (λ=0.81 μm) and an operating life of 2000 hours

Qantum-well AlGaAs/GaAs heterostructures with separate confinement have been used to fabricate laser diodes emitting at 0.81 μm, with a cw output optical power of 4 W and an operating life of more than 2000 h at a power of 3 W and a temperature of +20°C. Pis’ma Zh. Tekh. Fiz. 23, 90–94 (April 26, 1997)     

Quality assurance (QA) procedures for software: evaluation of an ADC quality system

Image viewing and processing software in computed radiography manipulates image contrast in such a way that all relevant image features are rendered to an appropriate degree of visibility, and improves image quality using enhancement algorithms. The purpose of this study was to investigate procedures for the quality assessment of image processing software for computed radiography with the use of existing test objects and to assess the influence that processing introduces on physical image quality characteristics. Measurements of high-contrast resolution, low-contrast resolution, spatial resolution, greyscale (characteristic curve) and geometric distortion were performed 'subjectively' by three independent observers and 'objectively' by the use of criteria based on pixel intensity values. Results show quality assessment is possible without the need for human evaluators, using digital images. It was discovered that the processing software evaluated in this study was able to improve some aspects of image quality, without introducing geometric distortion.     

Encapsulation of magnetic nanoparticles in a pH-sensitive poly(4-vinyl pyridine) polymer: a step forward to a multi-responsive system

A multiresponsive system that consists on pH-responsive polymer microspheres with encapsulated iron oxide magnetic nanoparticles that rendered the core magnetic to enable externally controlled actuation under magnetic induction has been developed. The inorganic nanoparticles were first prepared and, then, further encapsulated in a pH-sensitive poly(4-vinylpyridine). These spheres have been obtained by a modification of the simple, rapid and high-reproducible nanoprecipitation method. Magnetic measurements showed that the iron oxide nanoparticles are superparamagnetic and, therefore, able to undergo a local increase of the temperature when an oscillating magnetic field is applied. Magnetically triggered heating and pH sensitivity can be useful for biomedical applications.     

Enhanced optoelectronic,thermal, mechanical and third order nonlinear optical properties of dichlorobis(thiourea)zinc(II) crystal: an effect of Phenol red dye

For the first time the growth of dichlorobis (thiourea) zinc(II) (ZTC) monocrystal in presence of Phenol red dye of considerably good size (~13 mm?×?5 mm) has been achieved from aqueous solution using slow evaporation solution technique at room temperature. The solubility was calculated at different temperatures. The crystal structure was confirmed through X-ray diffraction analysis. The crystallinity of the dyed crystals has been enhanced revealed by Powder X-ray diffraction study. The presence of dye was inveterate by FT-IR and FT-Raman spectroscopic studies. The scanning electron microscopy analyses show that the grown crystals with dye are better than pure. Diffused reflectance was measured and optical band gap was calculated found to be enhanced from 4.5 to 4.65 eV for dyed crystals. The enhancement in the PL intensity has been observed in the dyed crystals. DSC study shows that the thermal stability has been remarkably enhanced from 163?°C (pure) to 203?°C (dyed) and various other thermal parameters are calculated. The surface study shows that the grown crystals with dye possess less dislocation than pure. Mechanical strength of the dyed crystal is found to be remarkably enhanced. Third-order nonlinear optical susceptibility (χ3) of PRZTC was found to be 2 times higher than pure. All results suggest that the properties of ZTC crystals grown in presence of dye are enhanced and can be considered as better contender in various nonlinear devices.     

Conversion of a direct to an indirect commercial (HFC134a/CO2) cascade refrigeration system: Energy impact analysis

Energy impact of conversion of a direct HFC134a/CO₂ cascade refrigeration system to an indirect HFC134a-secondary fluid / CO₂ cascade for commercial applications is experimentally analysed. Refrigeration systems, fully described, have been tested in laboratory conditions, at three condensing temperatures (25, 35 and 45 °C), providing the cooling needs to a cabinet for fresh product (2 °C) and to another for frozen product (−20 °C), both placed inside a climatic chamber simulating the indoor conditions of a supermarket. Energy evaluation considered 24 hour tests of stable operation in each test condition. A decrease from 1.9 to 3.5 K of the evaporation temperature of the high temperature cycle has been measured when using an indirect system. It resulted in a variation of the energy consumption of the whole system between 7.6 to 14.0% when using propylene-glycol/water and between −0.3 to 11.1% when using Temper −20^® as secondary fluid.     

Optimization of the process variables of roller compaction,on the basis of granules characteristics (flow,mechanical strength,and disintegration behavior): an application of SeDeM-ODT expert system

The objective of the study was application of SeDeM-ODT expert system for optimization of process variables for roller compaction and for the preparation of granules with better flow, compressibility, and disintegration behavior. In the present study, granules were prepared at pre-determined (on the basis of factorial design) process variables and characterized using SeDeM-ODT expert system. Compatibility of ribavirin with excipients (microcrystalline cellulose, tablettose-80, cross carmellose sodium, and magnesium stearate) was evaluated by binary mixture approach, using FTIR. According to the SeDeM-ODT expert system, granules were characterized for various parameters related to flow, compressibility and disintegration behavior and Index of Good Compressibility and Buccodispersibility (IGCB) was calculated. The process variables resulting in highest IGCB value were considered as optimum. Ribavirin was found compatible with all the excipients used in the study and characteristics peaks were present in FTIR spectra after subjecting to stress conditions (75% relative humidity at 45?±?5?°C) for 30?days. Both Ribavirin powder and Ribavirin containing powder blend had poor flow and compressibility while disintegration behavior was good due to higher water solubility. Screw speed of 35?rpm and roller speed at 12?rpm resulted in granules with acceptable characteristics. The IGCB value (5.63) of the granules was highest of all, indicating its better characteristics. SeDeM-ODT expert system presents a more practical picture of the granules and also predicts the mechanical strength and disintegration behavior of the tablets prepared from the granules. By proper optimization of screw and roller speed, efficiency of the process can be improved.