Advanced Layered Composite Structures for Underwater Acoustic Applications

The detection of underwater objects is one of the most critical technologies, and there have been constant efforts for developing sophisticated sonar systems in naval warfare. Against such efforts, the countermeasure of hiding underwater vehicles, equipment and weapons is another technological challenge. One of the effective countermeasures against sonic detection for the submarines and other underwater objects, such as naval mines, is to employ composite/hybrid materials to prevent ease of detection. Geometrical forms, shapes and layers, along with the tuning of the acoustical impedance, lead to a considerable decrease of the sonar signals via absorption of the sonic waves. In this study, an original and novel design of multi-layered composite/hybrid structure was developed and underwater acoustic testing procedures of reflection, transmission and scattering were applied in 80 kHz100 kHz frequency range. The findings obtained in this study showed that the multi-layered composite/hybrid materials with porous structure possess much lower values in millivolt than steel plates and might be potential candidates as covering and/or casing materials for underwater mines to reduce the acoustical signature against detection and identification

Thermophysical property measurements in electromagnetic levitators

Proper measurements of thermophysical properties of hot levitated liquid drops require the following: accurate temperature measurement (brightness measurement, emissivity measurement); precise drop shape measurements with submillisecond time resolution (density determination, rotational and vibrational shape information); precise control of drop shape (high symmetry variable gap levitators); accurate energy transfer measurements (direct measurements of energy transfer rates for defined gas flows over samples with quantitative measurements of energy transfer rates for defined flows over samples with known shapes); and precise measurements of repetitive sample motions (rapid repetitive shape measurements, frequency measurements with reflected laser light, measurements in the levitator and as a freely falling drop). Recent advances in coil design and control of sample rotation in an electromagnetic levitator are discussed with respect to the above requirements

Coaxial electrospinning of PVA/Nigella seed oil nanofibers: Processing and morphological characterization

One of the most promising nanostructures, core/shell structured co-axially electrospun nanofibers have been widely used in many applications such as self-healing, wound dressing/healing, drug and gene delivery and tissue engineering. Core/shell structured nanofibers have generally been produced using the coaxial electrospinning method. In this study, the coaxial electrospinning using the double injectors technique was applied for investigating the processing parameters for the PVA/Nigella seed oil solutions affecting the core/shell nanofiber morphology. Results showed that the processing parameters, such as the flow rate, voltage difference and solution concentration had significant effects on the core/shell nanofiber morphology. Nanofiber morphologies were characterized using SEM-Scanning Electron Microscopy techniques.Istanbul Development AgencyTurkiye Cumhuriyeti Kalkinma Bakanligi [ISTKA TR10/15/YNK/056]The authors would like to thank the Istanbul Development Agency for their support through the funding of Project No..ISTKA TR10/15/YNK/056

Structural Evolution and Microstructural Features of the Hydrodynamically Penetrating Copper Jet of a Shaped Charge

Shaped charges are unique and very effective warhead technology mostly applied to the rocket propelled grenades (RPGs) along with other applications (e.g. perforation of rocky formations in mining, rock drilling and other geological technics etc.). RPG's armour piercing and perforation performances originate from an explosively induced formation of a stretching metallic jet with very high velocities (hypervelocity). The hydrodynamic penetration mechanism of the stretching quasi-solid metallic jet is extremely complex and has not been fully understood. Both the jet with spout-like form and the target (i.e. RHA armour steel) behave hydrodynamically (i.e. incompressible fluid) and yet both solid strangely. The present study, as part of a large-scale customized R&D project, is stopping the penetration of the stretching jet of a RPG rocket within an "add-on" armour system. A series of experimental detonations and explosion of shaped charge munitions was conducted to elucidate the microstructural evolution and microstructural features of the metallic copper jet. Penetrating metallic spout-like jet forms were stopped and apprehended/caught within the inner layers of highly succesful composite based "add-on" armour designs. Structural evolution and microstructural analysis of the penetrating metallic jet were investigated to understand this extraordinary "solid-but behaving like fluid (quasi-solid)" metallic copper jet material. The findings obtained in this study suggest that the effective way of stopping the lethal effects of this weapon could be managed by diverting and/or twisting its linear stretching and penetration pathway.State Planning Organization of Turkish RepublicAuthors would like to thank to the State Planning Organization of Turkish Republic for the support of the Project. Authors would like to thank to the Tetra for their support for the SEM microstructural analysis and EDS studies. Authors would also thank to the researchers and technicians of the Materials Institute of TUBITAK Marmara Research Center for their support and work during the detonation-explosion experiments

Self-assemblying behaviour of activated microporous carbon microspheres functionalized via water filtration process

Activated carbon spheres are truly innovative materials with their porous micro/nanostructure that gives them tunable and controllable surface properties (i.e. high surface area, size and orientation of pores etc.). They have great potential for applications as adsorbents for cleaning/purification of water, air and chemical substances, catalyst supports, energy storage and conversion, adsorption of chemical warfare agents, filtration and others. Magnetic functionalization of highly porous and high surface areas of activated carbons have received considerable attention for their more sophisticated and advanced utilization as "smart" and "self-assemblying" purposes. In this study, a novel fabrication technique was used to synthesize activated high compressive strength nanoporous carbon spheres. The functionalization via adsorption/impregnation of magnetic substances was occured during a well-known water treatment-filtering route to fill the pores with nano-sized magnetic particles. Unusually active and dynamic interactions of the magnetic phases were observed upon contacting into each other revealing self-assemblying behaviour of activated carbon microspheres. Dynamic magnetical interaction of self assemblying behaviour of these spheres may have further and advanced applications for variety of purposes

Single-needle electrospinning of PVA hollow nanofibers for core-shell structures

As one of the most promising nanostructures, core-/shell-structured nanofiber has been widely used in many applications such as self-healing, drug and gene delivery, and tissue engineering. Hollow or core-/shell-structured nanofibers have generally been produced using single-needle and/or coaxial electrospinning methods. This method involves occurrence of varying sizes of bead formation. In this study, a single-needle electrospinning technique is applied for investigating the processing parameters affecting the fiber morphology and the bead formation in order to understand this innovative technique for further studies. Results showed that the parameters such as the voltage difference, collector distance and solution concentration have significant effects on the shell fiber morphology and the occurrence of bead formation.Istanbul Development AgencyTurkiye Cumhuriyeti Kalkinma Bakanligi [ISTKA TR10/15/YNK/056, TR10/16/YNY/0016]The authors would like to thank the Istanbul Development Agency for their support through the funding of the Project Nos. ISTKA TR10/15/YNK/056 and TR10/16/YNY/0016

Advanced Layered Composite Structures for Underwater Acoustic Applications

The detection of underwater objects is one of the most critical technologies, and there have been constant efforts for developing sophisticated sonar systems in naval warfare. Against such efforts, the countermeasure of hiding underwater vehicles, equipment and weapons is another technological challenge. One of the effective countermeasures against sonic detection for the submarines and other underwater objects, such as naval mines, is to employ composite/hybrid materials to prevent ease of detection. Geometrical forms, shapes and layers, along with the tuning of the acoustical impedance, lead to a considerable decrease of the sonar signals via absorption of the sonic waves. In this study, an original and novel design of multi-layered composite/hybrid structure was developed and underwater acoustic testing procedures of reflection, transmission and scattering were applied in 80 kHz-100 kHz frequency range. The findings obtained in this study showed that the multi-layered composite/hybrid materials with porous structure possess much lower values in millivolt than steel plates and might be potential candidates as covering and/or casing materials for underwater mines to reduce the acoustical signature against detection and identification

Drug-Induced Liver Injury by Glatiramer Acetate Used for Treatment of Multiple Sclerosis

Glatiramer acetate (GA, Copaxone) is an approved drug for the treatment of relapsing–remitting multiple sclerosis. Most common side effects observed with GA are local injection site reactions, which can include pain, swelling, or redness. However, systemic adverse event such as hepatotoxicity related to GA is rarely seen. In this report, we present a case of GA-induced toxic hepatitis associated with cholestatic and hepatocellular damage