3,224 research outputs found

    Numerical research of heated up to high temperatures particle influence on human skin

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    Numerical research results of heated to high temperatures particle influence on human skin are presented. The problem is solved in two-dimensional statement in Cartesian system of coordinates. The typical range of influence parameters of heated particle is considered. Temperature distributionы in different moments of time are obtained

    Electromagnetic heating processes: analysis and simulations

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    Electromagnetic heating (EMH) processes are being increasingly used in the industrial and domestic sectors, yet they receive relatively little attention in the thermal engineering domain. Time-temperature characteristics in EMH are qualitatively different from those in conventional heating techniques due to the additional parameters (viz dielectric properties of the material, size and shape of the product and process frequency). From a unified theory perspective, a multi-purpose model has been developed in order to obtain the heating characteristics for an arbitrary processing situation. Theoretical analyses of various EMH processes in materials of various regular geometries and a range of physical properties have been undertaken. Despite the wide spread usage of microwave energy in the food engineering sector. few understand microwaves and their interactions with foods. Much of the published research is largely focussed from the view point of an electrical engineer and aimed at the oven designer. However, trial-and-error methods are usually employed when developing microwavable food products and when using microwave ovens. The presented thesis is focussed from the view-point of the thermal engineer and aimed primarily at food developers and end users. The multi-purpose model was then modified specifically for simulating the heating of food materials in a microwave oven. The validity of the commonly made assumptions was investigated; in particular the variation of dielectriC properties during the heating processes and their likely influence on the model's predictions. Experimental data available in the literature were compiled and analysed to form a set of equations for predicting the dielectric properties of various food materials. Also available correlations for thermal properties were evaluated for a selected set of experimental data of different food materials. Analyses were undertaken to demonstrate and evaluate the effects of various parameters on the heating characteristics of different food materials commonly heated/cooked in microwave ovens. A qualitative comparison of model predictions and experimental measurements is provided to validate the physical basis of the model. Findings from the model lead to a better understanding of the interactions between foods and microwaves. [...cont.

    Experimental and numerical studies of thermoregulating textiles incorporated with phase change materials

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    Phase change materials (PCMs) provide thermal management solution to textiles for the protection of wearer from extreme weather conditions. PCMs are the substances which can store or release a large amount of energy in the form of latent heat at certain melting temperature. This research reports practical and theoretical studies of textiles containing PCMs. Mono and multifilament filaments incorporated with microencapsulated phase change material (MPCM) have been developed through melt spinning process. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) have been performed for the characterisation of MPCM polypropylene filaments. The parameters for optimum fibre processing and their effect on mechanical properties of filaments with respect to the amount of MPCM have also been studied. A plain woven fabric has been constructed using the developed MPCM multifilament yarn. The heat transfer property of the multifilament yarn and fabric has been investigated using finite element method. The time dependent thermoregulating effect of yarn and fabric incorporated with MPCM has also been predicted according to the validated models. The synthesis of Nanocapsules containing mixture of paraffins and Glauber’s salt as PCM and its characterisation using DSC and SEM has also been carried out. Polypropylene monofilament incorporated with the nanoencapsulated paraffins was developed and its properties have been compared to its MPCM counterpart. Furthermore the developed nanocapsules were applied on a cotton fabric via a pad-dry-cure process and the resultant fabric was evaluated using DSC and SEM in comparison with MPCM treated fabric. The research work described in this thesis has established a better understanding of use of phase change materials in textiles, the evaluation and application. It is anticipated that this research will broaden the understanding and potential use of encapsulated phase change materials in textiles especially in the field of active smart textiles

    Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

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    The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids

    Thermal analysis in a triple-layered skin structure with embedded vasculature, tumor, and gold nanoshells

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    In hyperthermia skin cancer treatment, the objective is to control laser heating of the tumor (target temperatures of 42-46 °C) so that the temperatures of the normal tissue surrounding the tumor remains low enough not to damage the normal tissue. However, obtaining accurate temperature distributions in living tissue related to hyperthermia skin cancer treatment without using an intruding sensor is a challenge. The objective of this dissertation research is to develop a mathematical model that can accurately predict the temperature distribution in the tumor region and surrounding normal tissue induced by laser irradiation. The model is based on a modified Pennes\u27 equation for the bioheat transfer in a 3-D triple-layered skin structure embedded with a vascular countercurrent network and a tumor appearing in the subcutaneous region. The vascular network is designed based on the constructal theory of multi-scale tree-shaped heat exchangers. The tumor is injected with gold nanoshells in order to be heated quickly. The proposed model is implemented numerically using a stable finite-difference scheme. To determine the laser intensity so that an optimal temperature distribution can be obtained, we pre-specify the temperature elevations to be obtained at the center of the tumor and on some locations on the perimeter of the skin\u27s surface. Using the least squares method, we obtain the optimal laser power and develop a computational procedure to obtain the temperature distribution. The method was tested in a 3-D triple-layered skin structure embedded with a vascular countercurrent network and a tumor appearing in the subcutaneous region. Gold nanoshells are assumed to have been injected into the central region of the tumor. The tumor region that has the gold nanoshells has ? x 109 particles/cm3 for each voxel of 0.01 cm x 0.01 cm x 0.001 cm. The tempeature is elevated by means of laser irradiation. The results show that the nanoshells have an effect on the tumor by heating the entire tumor to above 42 °C while not overheating the surrounding tissue. In comparison, results show that without nanoshells in the tumor region the tumor does heat up along its central axis; however, the perimeter of the tumor fails to reach 42 °C while the top of the skin reaches undesirable temperature levels due to the laser intensity required to heat the tumor. Such research may provide a useful tool for optimizing laser irradiation to kill the tumor while keeping the damage to the surrounding healthy tissue to a minimum (≤ 42 °C) during the hyperthermia cancer treatment

    Direct Metal Laser Sintering of Titanium implant with Tailored structure and Mechanical Properties

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    Direct Metal Laser Sintering has attracted much attention over the last decade for producing complex parts additively based on digital models. The capability and reliability of this process has stimulated new design concepts and has widened the manufacturing perspective of product customisation. This research work is designed to gain a deep understanding of laser sintering processing parameters, the corresponding microstructures and the mechanical properties. The main purpose is to have a body of fundamental knowledge about the laser and titanium powder material interactions, thus establishing the factors that influence the process-structure-properties relationships of the Direct Metal Laser Sintering process. Finally, a route for manufacturing customised craniofacial implants was described. This is to evaluate the DMLS processing capabilities in medical areas, particularly those parts having porous and lattice design structures. The interaction between a laser beam and the powder bed creates a distinctive structure; a ball shaped (blob) consists of solid and porous regions. All the blobs have the same shape and morphology which may well suggest that there is a tendency for the powder particles to form a spherical droplet prior to a movingless laser beam. Surrounding the melted core is a sintered region of partially melted powder particles where the powder particles were fused together to form inter-particle necks. There is a linear relation between size, weight and density of a blob and the laser power. The surface temperature obtained exceeds the melting and vaporization temperature of the titanium and this creates a hole on the top part of a blob as a result of a massive temperature rise. Laser power of 140W gives a consistent structure and hardness in a blob. Metallographic analyses of a blob’s cross-section show an α+β structure with prior-beta grains. The morphology of the lamellar structure consisted of acicular needles with a basket-weave pattern. The pores were characterised as having flat and spherical features with the size ranging from 2µm to 6µm. The micro-porosity observed may be associated with shrinkage which occurs during solidification or with the presence of entrapped gases from the atmosphere or argon gas from the shrouding environment Laser power and scan speed are the two most crucial factor controlling the laser-powder interactions. Result shows that laser power is capable of widening the processing parameters particularly the scan speed. Increased laser power causes more powder to melt thus creating a bigger melt pool. Contrary to this, increasing the scan speed reduces the interaction time thus a smaller amount of powder melts. The right combination of these two parameters results in inducing an appropriate exposure time where continuously scanned tracks can be formed. Most of the parts were successfully built using a specific volume energy density of 50Jmm⁻³, which was considered to be the optimum processing parameter for this research work. The ideal laser-material interaction time was calculated at 0.0008secs. The microstructural analysis revealed a fully lamellar structure with acicular morphology. XRD analysis confirmed the presence of α’ martensite, which explains the thermal history of a high isothermal condition and rapid cooling. The cross section of a solid part exhibited an acicular, needle-like structure with a herring bone pattern, parallel to building direction, due to directional solidification. The microstructure had a high tensile strength but with low ductility. It is also worth mentioning that a slight change in scan speed, with the intention of providing more energy density to the powder, may cause instability in the melt pool and cause deterioration in the mechanical properties. It is therefore confirmed that there is an upper limit and allowable processing window where a good balance of tensile strength and hardness in a DMLS part is achievable. A framework prior to an implant’s fabrication was established and the associated design and manufacturing software are reported. The processing route required software like MIMICS and MAGICS to manipulate the medical images and design data and equitable skills must be acquired to handle the machine in order to successfully fabricate the desired parts. Employing MAGICS new lattice function proved to be more efficient, saving time compared to a manual procedure, especially when dealing with large medical data manipulation. In conclusion, the proposed method from this study is capable of producing a customised part with the highest degree of design complexity compared with other conventional manufacturing methods. This has proved to be very suitable for manufacturing titanium medical implants, particularly craniofacial implants which require a customised and lightweight structure and at the same time still provide good mechanical propertie

    Novel formulations for magnetic-resonance imaging guided theranostics

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    Recent advances in bioimaging, biochemistry and bioinformatics have facilitated the development of personalized and precision medicine. Theranostics, a combination of imaging modalities and therapeutic agents, have garnered increasing attention in this context, thanks to their potential to monitor and control treatment for individual patients. An attractive strategy to achieve this goal involves the development of therapy guided by magnetic resonance imaging (MRI). MRI, possessing a number of benefits including a high degree of soft tissue contrast, low invasiveness, high depth of penetration and good spatial resolution, could offer advanced imaging-guided therapy enabling precise and time-resolved assessment of disease conditions and therapeutic progression. The goal of this PhD thesis is to develop novel formulations based on polymeric, inorganic or hybrid materials using two pharmaceutical fabrication techniques (electrohydrodynamic atomisation or spray drying), and explore their potential in MRI-guided chemotherapy. Five different types of formulation carrying MRI contrast agents and chemotherapeutic agents were fabricated. Chapter 3 reports the fabrication of pH-responsive formulations via electrodynamic atomization, loaded with superparamagnetic iron oxide nanoparticles (SPIONs) as contrast agents and the model chemotherapeutic carmofur. These platforms are able to protect the cargo from release acidic conditions representative of the stomach, while at neutral pH the relaxivity is tightly correlated to the extent of drug release. Chapter 4 describes a series of dual responsive systems with distinct morphology, comprising of pH-responsive Eudragit shells with SPIONs, and thermo-responsive core loading carmofur. The fibres are found to have better thermo-responsive properties compared to microparticles, and the relaxivity display clear linear relationships with drug release data. Chapter 5 focuses on using spray drying to fabricate nano-in-micro particles based on a synthetic polymer with an upper capital solution temperature. The microparticles encapsulate drug-loaded layered double hydroxide nanosheets, have thermo-sensitive release and relaxivity profile, and in vitro cell studies reveal that the formulations permit synergistic hyperthermia-aided chemotherapy. Chapter 6 details the preparation and characterization of four gadolinium doped layered double hydroxides to develop theranostic platforms carrying chemotherapeutics with high T1-relaxivity. In Chapter 7, polydopamine-coated polycaprolactone/poly(lactic-co-glycolic) acid nanofibers are developed via co-axial electrospinning, which are loaded with dug-loaded LDH nanocomposites in the core. In vitro studies reflect sustained release of chemotherapeutics, and highly effective cytotoxic effects on tumour cells with the polydopamine coated formulations, which was further enhanced at higher levels of glutathione

    Medical Laser-Induced Thermotherapy - Models and Applications

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    Heat has long been utilised as a therapeutic tool in medicine. Laser-induced thermotherapy aims at achieving the local destruction of lesions, relying on the conversion of the light absorbed by the tissue into heat. In interstitial laser-induced thermotherapy, light is focused into thin optical fibres, which are placed deep into the tumour mass. The objective of this work was to increase the understanding of the physical and biological phenomena governing the response to laser-induced thermotherapy, with special reference to treatment of liver tumours and benign prostatic hyperplasia. Mathematical models were used to calculate the distribution of light absorption and the subsequent temperature distribution in laser-irradiated tissues. The models were used to investigate the influence on the temperature distribution of a number of different factors, such as the design of the laser probe, the number of fibres, the optical properties of the tissue, the duration of irradiation, blood perfusion and boundary conditions. New results concerning transurethral microwave thermotherapy were obtained by incorporating the distribution of absorbed microwaves into the model. Prototypes of new laser applicators for anatomically correct treatment of benign prostatic hyperplasia were developed and tested ex vivo. Experimental work on liver tumours pointed to the importance of eliminating the blood flow in the liver during treatment to reduce convective heat loss. In addition, it was shown that hepatic inflow occlusion during treatment increased the thermal sensitivity of tumour tissue. The dynamic influence of interstitial laser thermotherapy on liver perfusion was investigated using interstitial laser Doppler flowmetry. Vessel damage after the combined treatment of laser-induced heat treatment and photodynamic therapy was studied

    The Thirteenth Annual Conference YUCOMAT 2011: Programme and the Book of Abstracts

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    The First Conference on materials science and engineering, including physics, physical chemistry, condensed matter chemistry, and technology in general, was held in September 1995, in Herceg Novi. An initiative to establish Yugoslav Materials Research Society was born at the conference and, similar to other MR societies in the world, the programme was made and objectives determined. The Yugoslav Materials Research Society (Yu-MRS), a nongovernment and non-profit scientific association, was founded in 1997 to promote multidisciplinary goal-oriented research in materials science and engineering. The main task and objective of the Society has been to encourage creativity in materials research and engineering to reach a harmonic coordination between achievements in this field in our country and analogous activities in the world with an aim to include our country into global international projects. Until 2003, Conferences were held every second year and then they grew into Annual Conferences that were traditionally held in Herceg Novi in September of every year. In 2007 Yu-MRS formed two new MRS: MRS-Serbia (official successor of Yu-MRS) and MRS-Montenegro (in founding). In 2008, MRS – Serbia became a member of FEMS (Federation of European Materials Societies)

    Sand and Dust on Mars

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    Mars is a planet of high scientific interest. Various studies are currently being made that involve vehicles that have landed on Mars. Because Mars is known to experience frequent wind storms, mission planners and engineers require knowledge of the physical and chemical properties of Martian windblown sand and dust, and the processes involved in the origin and evolution of sand and dust storms
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