Sušenje vlažne snovi je ena izmed najstarejših procesnih tehnik, ki se uporablja na številnih industrijskih področjih. Sušenje je zapleten fizikalni proces, ki obsega vezan večfazni prenos toplote, snovi in gibalne količine. Pri sušenju delcev, kot je na primer razpršilno sušenje, je čas sušenja odvisen od lokalnih pogojev v sušilnem plinu, in sicer na poti vsakega posameznega delca skozi sušilnik. Iz tega razloga je zelo pomembno poznavanje temperaturnega polja kot tudi polja vlažnosti v sušilniku, ki se zaradi toplotne in masne izmenjave med delci in sušilnim plinom nenehno spreminja. V prispevku je obravnavan numerični model za izračun sušenja poroznih delcev v toku sušilnega plina, pri čemer je reševanje problema izvedeno v sklopu Euler-Lagrange modela računske dinamike tekočin, in sicer z metodo robnih elementov. Povezava med delci in tokom tekočine je izvedena z nadgradnjo modela točkovnega izvora, ki upošteva konvektivni prenos toplote in snovi v sušilnem plinu. Testni izračuni potrjujejo primernost in pomembnost razvitega numeričnega modela za prostorski in časovni izračun sušenja delcev v toku sušilnega plina.
Dynamic thermography is a promising new non-invasive diagnostic technique for skin cancer, not just to identify the skin tumour in its early stage but also to evaluate some of tumour parameters showing the stage and invasiveness. This paper covers the solution of inverse bioheat problems of simultaneous identification of tumour diameter, thickness, blood perfusion rate and thermoregulation coefficient based on the surface temperature difference between healthy skin and lesion during the rewarming period of dynamic thermography. The problem has been treated using numerically generated measurement data for Clark II and Clark IV tumours by adding noise to mimic real measurement data. The solution is based on a more realistic 3D numerical model, composed of different layers including the thermoregulation response of the skin, tumour and surrounding tissue using a deterministic Levenberg–Marquardt optimisation algorithm that is robust and fast. The paper covers the analysis of the starting point of the solution, randomness and level of added noise, as well as the effect of numerical model error on the inverse solution. Tumour diameter and thermoregulation response can be estimated accurately regardless of noise and stage, while blood perfusion and tumour thickness can only be estimated accurately for low noise level or later tumour stage. The solution sensitivity to metabolic heat generation, thickness, blood perfusion rate and thermoregulation coefficient of skin and fat was low, while heat capacity and thermal conductivity of skin and tumour should be determined precisely in the numerical model to be able to evaluate all four tumour parameters as accurately as possible.
In filling lines equipped with membrane separation devices in the form of filters energy, consumption is only one of the important working parameters, the other being sustainable filter performance in terms of separation efficiency. As the filling line is typically equipped with a valve, intermittent operation of the filter is an important form of its use. Whereas the overall energy consumption of the filtration process is governed by the continuous operation mode, the intermittent mode, characterised by opening/closing of the valve, contributes most to problems of filter failure, i.e., the breakthrough of filtered particles through the membrane. A model for determination of the energy intake of a microfiltration membrane during the opening and closing of a valve is presented in this work. The model is based on computational analysis of the pressure wave signals recorded during the opening/closing of the valve using Fourier transform, and expressed in a nondimensional filter area specific energy intake form. The model is applied to a case of constant pressure dead-end microfiltration with three filter types: a single membrane filter, a stacked filter and a pleated filter with filtration surface areas ranging from 17.7 cm2 to 2000 cm2. Both clean filters, as well as partially clogged filter cases are taken into account. Second order polynomial models of the energy intake are developed and evaluated based on extensive analysis of the experimental data. The analysis of energy intake results show that the largest energy intake was observed for the clean filter case. When membrane fouling occurs at the constant flow rate values it leads to larger energy intake, however, due to a decreasing specific flow rate during fouling these values do not exceed the clean filter case.
Inovativnost in sprejemanje inovacij je pogoj, da se družba razvija in ostaja konkurencna. Pri tem ima vedno vecjo vlogo racunalniska tehnologija, katere razvoj je ravno v zadnjih petnajstih letih omogocil velik napredek na podrocju racunalnisko podprtega inženirstva. Racunalnisko podprto konstruiranje in racunalnisko inženirstvo z metodo koncnih elementov sta dandanes prakticno nepogresljiva. V diplomskem delu bo predstavljena uporaba komercialnega mednarodno priznanega programa Abaqus/CAE, s katerim bodo narejene analize trdnosti staticno obremenjene kovinske strehe stadiona s snežno obremenitvijo. Analize bodo opravljene na treh razlicnih konstrukcijah, ki bodo sestavljene iz konstrukcijskih elementov, katerih debeline sten bodo enake. Na koncu bo narejena SWOT analiza posamezne konstrukcije ter bodo podane resitve oz. možnosti za izboljsavo posamezne konstrukcije.
Sušenje je eno izmed pomembnejših in hkrati najstarejših področij procesne tehnike. Ena izmed zelo uveljavljenih oblik sušenja je razpršilno sušenje, ki je zelo pogosto prisotno v živilski, farmacevtski in kemijski industriji. V danem prispevku obravnavamo karakterizacijo formiranja spreja na razpršilni šobi in izvedbo numerične simulacije z vključenim sekundarnim razpadom spreja. Karakterizacija spreja na šobi je bila izvedena na sistemu Oxfor laser, medtem ko je za izvedbo numeričnih simulacij bil uporabljen programski paket Ansys Fluent. Primerjava rezultatov je pokazala dobro ujemanje med velikostno porazdelitvijo delcev pridobljeno pri eksperimentu in pri numerični simulaciji.
This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the Ultrasonic Spray Pyrolysis technique. The particle size was predicted accurately using a modified equation, and they were collected in a water suspension with Polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with Transmission Electron Microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a Polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was successfully extruded successfully, so that a 3D printed technology Fused Filament Fabrication could be used further for the production of tensile test tubes. The tensile tests showed that the addition of lyophilised Ni/Y2O3 into the PLA matrix decreased the tensile strength by 21.8 %, while the tensile modulus was not influenced. Dynamic Mechanical Analysis (DMA) showed that the addition of the Ni/Y2O3 particles increased the glass transition temperature by 5 °C, and increased the storage modulus in the glass transition range significantly. These findings demonstrate the potential for utilising Ni/Y2O3 nanocomposite particles in 3D printing applications, and warrant further exploration of their mechanical properties and potential applications in various fields.
The paper reports on development of a Boundary Element Method (BEM) based two phase dispersed flow model, that allows an accurate and efficient heat and mass transfer coupling by using a moving point source model to account for particle–fluid interaction. The two-way coupling model highlights the efficient use of the elliptic fundamental solution and the Dirac delta distribution properties to accurately evaluate the heat and mass point particle source impact on the continuous phase, solved by the Boundary Domain Integral Method (BDIM). In addition to the BDIM model of the particle–fluid heat and mass transfer interaction, the two-phase flow case under consideration is extended to the case of porous spherical particle drying with internal moving drying front, which is solved by the Boundary Element Method. As the two-phase flow is considered to be dilute, the particle–fluid momentum exchange is covered by a one-way coupling algorithm, with Lagrangian particle tracking used for determination of particle positions and velocities in the flow. Two computational cases are presented, where 1000 and 10000 particles are dried in a stream of hot air. Comparison between the obtained drying times for the cases of the one-way and the two-way heat and mass transfer coupling results shows, that the developed two-way coupling model accurately captures the effect of moisture accumulation and temperature decrease in the fluid phase, leading to realistic computations of drying rates of particles in the flow.
Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed that the recovery of gold nanoparticles from lateral flow immunoassays is possible, and the newly synthesised gold nanoparticles represent the possibility for incorporation into new products.
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