Characterisation of mechanical and thermal properties of double base propellant

WOS: 000282003600007A double base propellant is a polymer which is used as an energetic material to propel rockets. Advances in computers are making it possible to simulate a rocket as a whole, i.e. structurally and thermally. Among the rocket elements, little literature exists regarding the thermal and mechanical properties of propellants at a specified environment. In this study, a double base propellant is produced and then characterised. Accordingly, tensile specimens of the propellant are prepared according to JANNAF specifications to determine its mechanical properties. The tests are carried out at a possible 74 degrees C and also at varying crosshead speeds of 1.3, 6 and 30 mm min(-1). As of the thermal properties, the heat conduction coefficient, the specific heat and the density have been determined. All these properties complete the basic data for a thermomechanical simulation of a rocket on computer

Parameters optimization for horizontally built circular profiles: Numerical and experimental investigation

Selective laser melting (SLM), a type of additive manufacturing (AM) process, is chosen for direct fabrication of powder-based functional metallic objects. The designing of small circular geometries or overhang surfaces built parallel to platform bed has been a subject of concern in the industrial application of SLM. This paper presents an attempt to design and fabricate horizontally built circular holes in a simple cubic model in SLM machine. The processing parameters for down-skin such as laser power, scan speed, and the number of scanned layers were found to play a significant role in the sustainability of small hole built without support structures. The lower incident energy in down-skin region prevents excess melting of powder particles. The Numerical study on ANSYS was first carried out to identify the melt pool depth with different processing parameters and later SLM machine was used to produce the specimens for visual inspection. The results were found satisfactory with the application of down-skin parameters (65 W, 1000 mm/s) subjected to scanning of 3-5 layers above the exposed surface

Numerical investigation of heat current study across different platforms in SLM processed multi-layer AlSi10Mg

Selective Laser Melting (SLM) of three dimensional multi-layer model is being numerically investigated using finite element method with academic ANSYS software. The temperature distribution and melt pool formation with underlying solid base, support structure and loose powder is investigated in a single scan track. The results illustrate that the melt pool depth is deepest with the loose powder base but the regions adjacent to solid surface reduces the pool depth due to improved heat dissipation. Moreover, the liquid penetration increases with the layer addition and its intensity is dependent on input specific energy. The study suggests the selection of lower specific energy in the initial layers while designing overhang surfaces, clearance etc. to prevent excess powder melting beyond the layer thickness to achieve smooth surface

Current therapeutic approaches to equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis is the most important infectious neurologic disease of horses in the Western Hemisphere. Equine protozoal myeloencephalitis can interfere with a horse\u27s ability to race, work, and perform; untreated, EPM can be lethal. Antemortem diagnosis of EPM is challenging, requiring careful evaluation of the animal\u27s history, clinical signs, and laboratory data, with rigorous exclusion of other causes. Therapeutic approaches to EPM are evolving. First-generation therapeutic approaches for EPM were based on the classic anti–Toxoplasma gondii pyrimethamine–sulfonamide combinations; treatment is prolonged and can be associated with a considerable relapse rate, which may be associated with the difficulty in maintaining effective CNS concentrations of pyrimethamine. Second-generation therapeutic approaches are based on diclazuril and related triazine agentsa; in 2001, toltrazuril sulfoneb (ponazuril) became the first FDA-approved treatment for EPM. Triazine agents may have prolonged plasma half-lives, and their therapeutic efficacy would likely be enhanced by application of loading-dose schedules. A pyrimethamine-sulfonamide combination formulationc received FDA approval in 2004 for the treatment of EPM. Additionally, a diclazuril-based topical feed dressing formulationd received FDA approval in 2011. The ideal therapeutic agents for use against EPM would be effective when administered orally, with high efficacy against Sarcocystis neurona and minimal toxicity for horses. This article reviews the current information available for EPM, including the clinical pharmacology and efficacy of FDA-approved and nonapproved investigational medications for the treatment or prophylaxis of EPM. Equine protozoal myeloencephalitis is caused by 2 apicomplexan protozoal parasites: S neurona and, much less commonly, Neospora hughesi. Location of the causative organism in the CNS is random, so clinical signs of EPM are highly variable. Any combination of neurologic signs is possible, although spinal cord involvement is most common. Onset may be gradual or acute, with the usual pattern being mild clinical signs that progress with time. Furthermore, the intracellular localization of the causative organisms in the CNS creates difficulties for chemotherapeutic approaches and may also interfere with host-based immunologic defenses. Antemortem diagnosis of EPM is particularly challenging, requiring careful evaluation of the animal\u27s history, clinical signs, and laboratory data, with rigorous exclusion of other causes. Definitive diagnosis of EPM is dependent on necropsy detection of typical CNS lesions of the disease or presence of the appropriate causative organisms. Although careful clinical examination remains the most important antemortem diagnostic technique for EPM, laboratory methods have been developed to assist clinical diagnosis. As such, for horses with clinical signs consistent with EPM, it is optimal to perform immunoblotting, an indirect florescent antibody test, or ELISA analyses on blood and CSF samples prior to diagnosis and initiation of treatment. Preventative approaches to EPM are not well defined. Prevention of EPM with daily pyrantel tartratee administration at the current labeled dose has not been effective in immunocompetent horses1 or in interferon-γ knockout mice,2 even though the compound is active against S neurona in vitro.3 An EPM vaccine based on homogenates of S neurona merozoites with conditional licensure has been marketed for prevention of EPM, but this vaccine was removed from the market due to lack of efficacy data in prospective studies