Deviations Of Profiles Research Articles

Evaluation of Interfacial Structure of Self-Assembled Nanoparticle Layers: Use of Standard Deviation between Calculated and Experimental Drop Profiles as a Novel Method.

The self-assembly of nanoparticles (NPs) at interfaces is currently a topic of increasing interest due to numerous applications in food technology, pharmaceuticals, cosmetology, and oil recovery. It is possible to create tunable interfacial structures with desired characteristics using tailored nanoparticles that can be precisely controlled with respect to shape, size, and surface chemistry. To address these functionalities, it is essential to develop techniques to study the properties of the underlying structure. In this work, we propose an experimental approach utilizing the standard deviation of drop profiles calculated by the Laplace equation from experimental drop profiles (STD), as an alternative to the Langmuir trough or precise microscopic methods, to detect the initiation of closely packed conditions and the collapse of the adsorbed layers of CTAB-nanosilica complexes. The experiments consist of dynamic surface/interfacial tension measurements using drop profile analysis tensiometry (PAT) and large-amplitude drop surface area compression/expansion cycles. The results demonstrate significant changes in STD values at the onset of the closely packed state of nanoparticle-surfactant complexes and the monolayer collapse. The STD trend was explained in detail and shown to be a powerful tool for analyzing the adsorption and interfacial structuring of nanoparticles. Different collapse mechanisms were reported for NP monolayers at the liquid/liquid and air/liquid interfaces. We show that the interfacial tension (IFT) is solely dependent on the extent of interfacial coverage by nanoparticles, while the surfactants regulate only the hydrophobicity of the self-assembled complexes. Also, the irreversible adsorption of nanoparticles and the increasing number of adsorbed complexes after the collapse were observed by performing consecutive drop surface compression/expansion cycles. In addition to a qualitative characterization of adsorption layers, the potential of a quantitative calculation of the parameter STD such as the number of adsorbed nanoparticles at the interface and the distance between them at different states of the interfacial layer was discussed.

Wind induced peak pressures on low-rise building roofs via dynamic terrain computational methodology

Computational Wind Engineering is expanding rapidly in the last decade and is expected to be introduced as a design tool for wind-induced loads in future code provisions and standards worldwide. The paper discusses the current CWE shortcomings of the state-of-the-art and proposes a methodology that targets to close the current research gaps, from a practical point of view. Monitoring wind tunnel experiments, significant deviations of instantaneous velocity profiles due to high turbulence intensity are expected to be critical for design pressures. This inspired the novel modeling technique - named Dynamic Terrain - that reformulates the turbulence characteristics and assumes that each instantaneous profile is produced by changing the corresponding terrain conditions. Successively derived profiles from the wind tunnel are introduced as inlet conditions in coarse LES computational domain and propagate inside the domain to interact with the building. The incident flow is successfully modelled, in terms of mean, turbulence intensity and spectral content. Mean, standard deviations and peak pressure coefficients correlate well with experimental results and the procedure is advantageous compared to similar computational techniques. The target accuracy is achieved, benefits and limitations of the method are discussed, and conclusions based on experimental and computational observations are drawn.

Wall-Modeled Large-Eddy Simulation of Turbulent Boundary Layer with Spatially Varying Pressure Gradients

Wall-modeled large-eddy simulations of turbulent boundary layers subjected to spatially varying streamwise pressure gradients are conducted to assess the predictive performance of three wall models: ordinary differential equation equilibrium, integral nonequilibrium, and partial differential equation (PDE) nonequilibrium models. The test case is based on experiments conducted by Volino (Journal of Fluid Mechanics, Vol. 897, Aug. 2020, p. A2), where the flow is subjected successively to zero pressure gradient (ZPG), favorable pressure gradient (FPG), recovery ZPG, and adverse pressure gradient (APG) regions. Skin friction is overpredicted in FPG by all the wall models. For equilibrium and integral models, this overprediction is attributed to the strong deviation of mean velocity profiles within FPG from the log law, used explicitly in the equilibrium and implicitly in the integral model. The overprediction is more pronounced for the PDE model, which is attributed to dynamic correction of wall-model eddy viscosity for resolved stresses and a lack of correction for pressure gradient. Potential remedies to mitigate this problem are proposed. Grid refinement improves wall-stress predictions in both FPG and APG but only affects the outer profiles in APG, revealing that accurate wall-flux modeling is more critical for APG. Anisotropic grid analysis shows streamwise grid refinement to be more crucial than spanwise for the convergence of skin-friction, outer velocity, and Reynolds stress profiles.

Calculation of the Tubular Elements Made of Pressed Profiles

This paper is dedicated to ensuring the strength of cargo equipment elements of transport aircraft. The strength of rollers of roller conveyors, which are made of standard pressed aluminum tubular profiles or composite tubular elements, is considered. The main disadvantage of these semi-finished products is the deviation of the diameter of these standard aluminum profiles, which leads to the emergence of eccentricity Δ between the axes of the outer and inner surfaces. The influence of eccentricity on the change in the values of normal and tangential stresses is considered. This analysis was carried out for standard diameters of tubular profiles at values Δ equal to half of the standard limit deviation of the outer diameter D. Calculations of normal and tangential stresses and their comparison with nominal stresses that occur in the absence of misalignment have been carried out. Calculations were made of the value c of the removal of the center of rigidity from the center of the circle of the outer border of the cross-section at different cross-section sizes of standard profiles with values of Δ equal to half of the standard limit deviation of the outer diameter D inclusively. The calculations showed an increase in tangential stresses τ in some cases by 64% and even by 213%. The obtained results indicate that the presence of Δ≠0 will have a negative effect on the resource of these elements. In order to eliminate the negative consequences, it is necessary to increase the requirements for the shape deviation of the tubular profiles in the input control.

Radial grid reflectance correction for hyperspectral images of fruits with rounded surfaces

Over the last two decades, the viability of hyperspectral imaging (HSI) technology as a tool for determining food quality has been established. This technology has been successfully combined with chemometric tools and image-processing techniques to enhance its effectiveness. Despite the advances in imaging technology, significant challenges related to non-uniformity caused by object geometry still need to be addressed. The inappropriate processing of non-uniform food products can significantly affect subsequent calculations, including accurate measurements and precise analysis. A popular method used to face up non-uniformity is the Lambertian surface correction, which assumes spherical surfaces of food products; however, it presents some issues with non-spherical shapes. This work proposes a generalized reflectance correction method for HSI of rounded fruits that are not necessarily spherical. The method is based on the correlation between the pixel’s position and its reflectance. For proof of concept, a case study was designed considering the HSI of mango fruits (Mangifera indica L) Kent variety. For comparison, each image was corrected using both the Lambertian surface correction and the proposed method. Results show a strong correlation between the standard deviation of the spectral profiles of images and the roundness of the fruit, which is more evident in the case of the proposed radial grid correction method. Hence, the proposed radial correction method produced a more uniform texture in corrected hyperspectral images.

A 1-D model to retrieve the vertical profiles of minor atmospheric constituents for cloud microphysical modeling: I. Formulation and validation

Determining the number concentration of minor constituents in the atmosphere is very important as it determines the whole tropospheric chemistry process. These constituents may act as cloud condensation nuclei (CCN) and ice nuclei (IN), impacting heterogeneous nucleation inside the cloud. However, the estimations of the number concentration of CCN/IN in cloud microphysical parameters are associated with uncertainties. In the present work, a hybrid Monte Carlo Gear solver has been developed to retrieve profiles of CH4, N2O, and SO2. The idealized experiments have been carried out using this solver for retrieving vertical profiles of these constituents over four megacities, viz., Delhi, Mumbai, Chennai, and Kolkata. Community Long-term Infrared Microwave Coupled Atmospheric Product System (CLIMCAPS) dataset around 0800 UTC (2000UTC) has been used for initializing the number concentration of CH4, N2O, and SO2 for daytime (nighttime). The daytime (nighttime) retrieved profiles have been validated using 2000 UTC (next day 0800 UTC) CLIMCAPS products. ERA5 temperature dataset has been used to estimate the kinematic rate of reactions with 1000 perturbations determined using Maximum Likelihood Estimation (MLE). The retrieved profiles and CLIMCAPS products are in very good agreement, as evidenced by the percentage difference between them within the range of 1.3 × 10−5–60.8 % and the coefficient of determination mainly within the range between 81 and 97 %. However, during the passage of tropical cyclone and western disturbance, its value became as low as 27 and 65 % over Chennai and Kolkata, respectively. The enactment of synoptic scale systems such as western disturbances, tropical cyclone Amphan, and easterly waves caused disturbed weather over these megacities—the retrieved profiles during disturbed weather cause large deviations of vertical profiles of N2O. However, the profiles of CH4 and SO2 have less deviation. It is inferred that incorporating this methodology in the dynamical model will be useful to simulate the realistic vertical profiles of the minor constituents in the atmosphere.

Urban ventilation assessment with improved vertical wind profile in high-density cities – Comparisons between LiDAR and conventional methods

The vertical wind speed profile is crucial to urban ventilation assessment and urban planning/design. This study uses Light Detection and Ranging (LiDAR) observation as benchmark to evaluate accuracy of wind profiles estimated by conventional methods. The conventional methods include Boundary Layer Wind Tunnel (BLWT), Regional Atmospheric Modeling System (RAMS), Power Law (PL), and Weather Research and Forecasting (WRF). The evaluation involves two typical urban sites with different densities under summer weak-wind conditions. Large Eddie Simulations (LES) are conducted to further investigate the sensitivity of urban ventilation assessment results to the deviations of wind profiles. The results indicate significant deviations in LES caused by conventional methods. The largest deviations of wind velocity ratio are found in mesoscale meteorological models (RAMS and WRF (>65%)). Deviations caused by physical and empirical models are smaller but still significant (BLWT (>25%) and PL (>40%)). Consequently, large deviations (>100%) of wind-relevant criterion for outdoor thermal comfort are observed. Finally, to balance accuracy and data availability, we recommend power law method as the optimal method to provide inflow boundary condition for numerical simulations when LiDAR observation is not available. We provide new and valuable understandings to improve urban ventilation assessment in high-density cities.

An axisymmetric flow analysis by means of tangent hyperbolic fluid with Cattaneo-Christov heat and mass flux model

In present analysis three dimensional steady, axisymmetric, incompressible, non-Newtonian tangent hyperbolic flow of nanofluid due to rotating disk is investigated. A rotating disc is a phenomena in which a disc rotates around an axis at a constant angular velocity and each point on the disc follows a circle's arc. The force necessary to move the disc to overcome frictional resistance is determined by the shear stress between the disc and the rotating fluid and the heat transfer is affected by the local flow field. The heat and mass transfer field is explored in the existence of chemical reaction and Cattaneo-Christov heat and mass flux model. By using similarities transformations, the supreme partial differential equations of the problem are turned into typical differential equations respectively. The determining differential equations are solved on MATLAB software by using bvp4c method that has been cracked through shooting technique. The deviation of velocity, temperature and mass profiles for different inputs of power-law index, Prandtl number, Brownian motion parameter, Schmidt number, thermophoretic parameter, heat and mass relaxation time parameters and chemical reaction parameter are displayed via graphs. The increment happens in radial velocity field whereas tangential and axial velocity fields reduces due to power index parameter n. The results show that for Cattaneo-Christov model, the temperature and concentration profiles exhibit reducing behaviour than that of Fourier's classical model. The concentration within fluid declined due to chemical reaction.

Comparative evaluation of fish larval preservation methods on microbiome profiles to aid in metagenomics research.

Applications of microbiome research through metagenomics promise to generate microbiome manipulation strategies for improved larval survival in aquaculture. However, existing lacunae on the effects of sample preservation methods in metagenome profiles hinder the successful application of this technique. In this context, four preservation methods were scrutinized to identify reliable methods for fish larval microbiome research. The results showed that a total of ten metagenomics metrics, including DNA yield, taxonomic and functional microbiome profiles, and diversity measures, were significantly (P < 0.05) influenced by the preservation method. Activity ranking based on the performance and reproducibility showed that three methods, namely immediate direct freezing, room temperature preservation in absolute ethanol, and preservation at - 20°C in lysis, storage, and transportation buffer, could be recommended for larval microbiome research. Furthermore, as there was an apparent deviation of the microbiome profiles of ethanol preserved samples at room temperature, the other methods are preferred. Detailed analysis showed that this deviation was due to the bias towards Vibrionales and Rhodobacterales. The microbial taxa responsible for the dissimilarity across different methods were identified. Altogether, the paper sheds light on the preservation protocols of fish larval microbiome research for the first time. The results can help in cross-comparison of future and past larval microbiome studies. Furthermore, this is the first report on the activity ranking of preservation methods based on metagenomics metrics. Apart from methodological perspectives, the paper provides for the first time certain insights into larval microbial profiles of Rachycentron canadum, a potential marine aquaculture species. KEY POINTS: • First report on effects of preservation methods on fish larval microbiome profiles. • First report on activity ranking of preservation methods based on metagenomics metrics. • Storage methods influenced DNA yield, taxonomic and functional microbiome profiles.

Нейросетевое моделирование фрактальной самоорганизации микробно‑организменных биосистем в кишечниках птиц

The purpose of this study was to determine feed probiotics, including Lactobacillus plantarum and Lactobacillus fermentum bacteria, which stimulate the bioconsolidation of microorganisms in the intestines of broilers, provide high efficiency of biochemical transformations of plant substrates in the intestines of birds and promptly supply the body of birds with all the necessary nutrients. To control the bio-consolidation (IndBcon) of the microbial community in the intestines of birds, it is proposed to calculate the bioconsolidation index according to the frequency-taxonomic profiles of operational taxonomic units (OTE) of microbial communities determined by the molecular genetic method. It is assumed that the high values of IndBcon correspond to the increased efficiency of biochemical processes of decomposition of fiber in the intestines of birds and the full development of birds. To determine the values of the IndBcon index, we selected a model fractal OTE profile in which the OTE frequencies are a log-arithmetic series of decreasing numbers (for example: log2 (0,125) = –3; log2 (0,25) = –2; log2 (0,5) = –1; ...). This makes it possible to calculate the IndBcon index based on the deviation of the real OTE profiles from the model fractal OTE profile, and by comparing the IndBcon values for different bird diets, determine the diet that ensures the bioconsolidation of the intestinal microflora. An artificial computational neural fractal network (NFS) was developed to analyze the profiles of the OTE microflora of the intestines of birds and calculate the IndBcon indices. The NSF can simultaneously process several OTE profiles (for all variants of the experiment) and calculate the IndBcon values for each variant, that is, to obtain a quantitative assessment of the impact of the diet of birds on the biconsolidation of the microbial community in the intestines of birds. An artificial computational neural fractal network (NFS) was developed to analyze the profiles of the OTE microflora of the intestines of birds and calculate the IndBcon indices. The NSF can simultaneously process several OTE profiles (for all variants of the experiment) and calculate the IndBcon values for each variant, that is, to obtain a quantitative assessment of the impact of the diet of birds on the biconsolidation of the microbial community in the intestines of birds. In this experimental and theoretical study, three OTE profiles obtained by molecular genetic method in one control group (group 1) and two experimental groups (groups 2 and 3) of birds were compared. A probiotic with the bacterium Lactobacillus plantarum was included in the feed diet of the 2nd group of birds, and a probiotic with the bacterium Lactobacillus fermentum was included in the feed diet of the 3rd group. Processing of three OTE profiles using NSF showed that in birds of group 1 IndBcon = 0,52, in birds of group 2 IndBcon = 0,24, in birds of group 3 IndBcon = 0,74. It turned out that these IndBcon values correlate with the masses of broilers in the corresponding groups (r=0,94), which confirms the influence of bioconsolidation of the microbial community of the intestines of birds on the activation of biochemical processes in the intestines of birds and their accelerated development of birds. Based on the study, it was recommended to use feed probiotics with Lactobacillus fermentum bacteria, since they help achieve the highest value of IndBcon and bioconsolidation of the intestinal microflora of birds.

Assessing Surface Texture Features of Asphalt Pavement Based on Three-Dimensional Laser Scanning Technology

Pavement surface texture features are one of key factors affecting the skid resistance of pavement. In this study, a set of stable and reliable texture measurement equipment was firstly assembled by using the linear laser ranging sensor, control system and data acquisition system. Secondly, the equipment was calibrated, and the superposition error of sensor and control system was tested by making a standard gauge block. Thirdly, four different kinds of asphalt mixture were designed, and their surface texture features were obtained by leveraging a three-dimensional laser scanner. Therefore, the surface texture features were characterized as one-dimensional profile features and three-dimensional surface features. At the end of this study, a multi-scale texture feature characterization method was proposed. Results demonstrate that the measurement accuracy of the laser scanning system in the x-axis direction can be controlled ranging from −0.01 mm to 0.01 mm, the resolution in the XY plane is 0.05 mm, and the reconstructed surface model of surface texture features can achieve a good visualization effect. They also show that the root mean square deviation of surface profiles of different asphalt pavements fluctuates greatly, which is mainly affected by the nominal particle size of asphalt mixture and the proportion of coarse aggregate, and the non-uniformity of pavement texture distribution makes it difficult to characterize the roughness of asphalt pavement effectively by a single pavement surface profile. This study proposed a texture section method to describe the 3D distribution of road surface texture at different depths. The macrotexture of the road surface gradually changes from sparse to dense starting from the shallow layer. The actual asphalt pavement texture can be characterized by a simplified combination model of “cone + sphere + column”. By calculating the surface area distribution of macro and microtextures of different asphalt pavements, it was concluded that the surface area of asphalt pavement under micro scale is about 1.8–2.2 times of the cutting area, and the surface area of macrotexture is about 1.4 times of the cutting area. Moreover, this study proposed texture distribution density to characterize the roughness of asphalt pavement texture at different scales. The SMA index can represent the macroscopic structure level of different asphalt pavements to a certain extent, and the SMI index can well represent the friction level of different asphalt pavements.

Mean Current Profile over Rippled-Beds in the Presence of Non-Breaking Waves and Analysis of Its Influencing Factors

Classical eddy viscosity model deviates from the actual mean current profiles, when calculating the mean current profiles over rippled-beds in the presence of non-breaking waves, owing to the neglect of the enhancement of the wave boundary layer thickness by ripples and the wave-induced shear stress (the radiation stress and the wave Reynolds stress). Considering these shortcomings, a semi-empirical one-dimensional vertical (1DV) model is presented in this study. The present model was obtained using the two-dimensional Navier–Stokes equations and eddy viscosity assumptions, which differ from those of previous researchers, while a top-to-bottom sequence was adopted to calculate the mean current profiles. Empirical formulae were derived from the laboratory measurements and used in the present model to accurately predict the wave boundary layer thickness and bed roughness. The present model is in satisfactory agreement with the data from laboratory experiments. The factors influencing the mean current profiles were analyzed also. The wave-induced second-order shear stresses were found to be the principal reason for the deviations of the mean current profiles in the near-surface layer; as the influencing factors of wave-induced shear stress, the intensity of the wave relative to the current, the angle between the wave and current, and the size of ripples can also have a non-negligible effect on the mean current profiles.

Detection of aerosol mass concentration profiles using single-wavelength Raman Lidar within the planetary boundary layer

Considering the importance of the aerosol optical parameters detection for environmental monitoring, a method of converting single-wavelength Raman lidar backscattered echoes to aerosol mass concentrations is proposed to obtain a high-resolution vertical distribution of particulate matter (PM) mass concentrations. PMx (x = 1, 2.5, 10) mass concentrations and extinction coefficients at 355 nm and 532 nm were obtained using a combination of a colocated visibility meter and wide-range particle spectrometer (WRAS), and parameterized equations between the aerosol extinction coefficient and mass concentration at different levels of relative humidity (RH) were established (the sample datasets included different seasonal and weather pollution conditions in Xi'an, China, for 2018 and 2019). The results demonstrate that parametric analysis of sample datasets at three levels of RH (RH < 60%, 60% ≤ RH < 75%, and RH ≥ 75%) can better reflect the long-term variation characteristics of aerosols: the aerosol extinction coefficients show an exponential relationship with PM1 and PM2.5 mass concentrations, and the correlation coefficients are both above 0.965 even at different levels of RH, while the correlation with PM10 is 0.808. The extinction coefficient and RH profiles can be retrieved using single-wavelength Raman lidar, and then the aerosol mass concentration distribution can be calculated by combining parameterized equations. The deviation of mass concentration profiles between 355 and 532 nm Raman lidar was analyzed, and it is a constraint that the calculation of the PM mass concentration profile is made in the planetary boundary layer (PBL). The derivation uncertainty of PMx and the limitations of the method are also discussed. Finally, cases of vertical distribution and variations in PMx on pollution-free and hazy days are presented.

Conformational dynamics of a multidomain protein by neutron scattering and computational analysis

The flexible conformations of a multidomain protein are responsible for its biological functions. Although MurD, a 47-kDa protein that consists of three domains, sequentially changes its domain conformation from an open form to a closed form through a semiclosed form in its enzymatic reaction, the domain dynamics in each conformation remains unclear. In this study, we verify the conformational dynamics of MurD in the corresponding three states (apo and ATP- and inhibitor-bound states) with a combination of small-angle x-ray and neutron scattering (SAXS and SANS), dynamic light scattering (DLS), neutron backscattering (NBS), neutron spin echo (NSE) spectroscopy, and molecular dynamics (MD) simulations. Applying principal component analysis of the MD trajectories, twisting and open-closed domain modes are identified as the major collective coordinates. The deviations of the experimental SAXS profiles from the theoretical calculations based on the known crystal structures become smaller in the ATP-bound state than in the apo state, and a further decrease is evident upon inhibitor binding. These results suggest that domain motions of the protein are suppressed step by step of each ligand binding. The DLS and NBS data yield collective and self-translational diffusion constants, respectively, and we used them to extract collective domain motions in nanometer and nanosecond scales from the NSE data. In the apo state, MurD shows both twisting and open-closed domain modes, whereas an ATP binding suppresses twisting domain motions, and a further reduction of open-closed mode is seen in the inhibitor-binding state. These observations are consistent with the structure modifications measured by the small-angle scattering as well as the MD simulations. Such changes in the domain dynamics associated with the sequential enzymatic reactions should be related to the affinity and reaction efficiency with a ligand that binds specifically to each reaction state.

Structural and activity changes of xanthine oxidase induced by cetyltrimethylammonium bromide and its Gemini homologue bis(cetyldimethylammonium)hexane dibromide: a comparative study

Interaction of xanthine oxidase (XOD), a key enzyme in purine metabolism, with cetyltrimethylammonium bromide (CTAB) and bis(cetyldimethylammonium)hexane dibromide (C16C6C16Br2) has been studied by employing different techniques at pH 7.4 and 25 °C. The existence of interaction between the surfactants and the enzyme was established by the deviation of tensiometric profiles of surfactants with and without the enzyme. The results obtained by Circular Dichroism, Fluorescence and activity suggest that the Gemini surfactant interacts strongly with the XOD than its conventional homologue. The peculiar structural design of C16C6C16Br2, enhanced ability for electrostatic and hydrophobic interactions, and unique aggregation behavior is accountable for the effectiveness of the Gemini in interacting/unfolding the XOD. The results are contemplated to offer valuable understandings in designing the surfactant-based formulations to moderate the activity of XOD.

Aerodynamic analysis and design optimization of a centrifugal compressor impeller considering realistic manufacturing uncertainties

Centrifugal compressor impeller blades inevitably suffer from manufacturing uncertainties. Such manufacturing uncertainties result in geometric deviations of blade profiles, and have been increasingly recognized to be detrimental to compressor performance. However, relevant studies on the uncertainty analysis and design optimization of centrifugal impeller blades are quite rare. The effect of realistic manufacturing uncertainties on impeller aerodynamic performance and flow field still remains unclear. Here we present a comprehensive investigation on deterministic analysis, uncertainty analysis and design optimization of a centrifugal compressor impeller with considerations of three-dimensional realistic manufacturing uncertainties. Through statistical analysis of blade profile measurements of machined centrifugal impellers, both the blade camber and thickness errors are confirmed to obey Gaussian distributions. The deterministic analysis results show that the positive thickness errors near the main blade leading edge are mainly responsible for impeller performance degradations because of aggravated flow separations especially at large flow rate. A bi-fidelity metamodel, namely sparse grid stochastic collocation-support vector regression (SGSC-SVR), is used to balance the efficiency and accuracy of the uncertainty analysis. The mean impeller performance is found to become more deteriorated as the mass flow rate increases while the uncertain band is smaller at the design point than at off design points. Finally, a sequential infilling sampling-based optimization method is employed to solve the design optimization. It is demonstrated that reduced blade angles are able to compensate the adverse effect of positive blade thickness errors and thus enhance the impeller performance robustness against manufacturing uncertainties. The present study lays a theoretical foundation for the further uncertainty quantification and robust design of advanced centrifugal compressors.

Study of Head Loss in Rapid Filtration with four River Sands

In this work, we studied the filtration behavior, with regard to the head loss, of four calibrated Togo Rivers sands compared to that of a reference filter sand imported from Europe. The objective is to determine the suitability of local rivers sands as filter sands for water treatment plants. The sands were successively loaded into a filtration pilot and subjected, during at least 20 hours, to the filtration of water whose turbidity was maintained at around 20 NTU. The results show that the average deviations of the head loss profiles as a function of depth, calculated in relation to the head loss recorded on the reference sand, at the same filtration time t=20h, are small and vary from 2 cm to 8 cm. In the same way, the curves of the head loss as a function of time are quite close to the one observed for the reference sand. Examination of the clogging front after 20 hours of filtration reveals that the progression is either the same or greater and reached 20 cm in depth at the same time. This study can be extended to other rivers sand samples and by varying the turbidity and the filtration rate. Doi: 10.28991/cej-2021-03091682 Full Text: PDF

ERO modelling of net and gross erosion of marker samples exposed to L-mode plasmas on ASDEX Upgrade

• Gross and net erosion studied in ASDEX Upgrade using Au and Mo marker coatings. • Largest erosion at the strike point and re-deposition small outside of the markers. • Based on ERO simulations, electron temperature has the largest impact on erosion. • A faint toroidal tail of re-deposited particles predicted downstream of the markers. • Re-deposition drops from >50% to <40% with marker size decreasing from 5 mm to 1 mm. In this paper, we report experimental and numerical investigations of gross and net erosion of gold (Au) and molybdenum (Mo), proxies for the common plasma-facing material tungsten (W), during L-mode plasma discharges in deuterium (D) in the outer strike-point region of the ASDEX Upgrade tokamak. To this end, erosion profiles of different marker spots (for Au, dimensions 1 × 1 and 5 × 5 mm 2 ) and marker coatings (for Mo) have been determined and modelled using the ERO code. The smaller marker spots were designed to quantify the gross-erosion rate while on the bigger markers local prompt re-deposition of Au allowed obtaining data on net erosion. The experimental results indicate relatively uniform erosion profiles across the marker spots or coatings, very little re-deposition elsewhere, and the largest erosion taking place close to the strike point. Compared to W, the markers show up to 15 times higher net erosion but no major differences in the poloidal migration lengths of Au and W can be seen. Gold thus appears to be a proper choice for studying migration of W in the divertor region. The ERO simulations with different background plasmas are able to reproduce the main features of the experimental net erosion profile of Au. Of the studied parameters, electron temperature has the strongest impact on erosion: doubling the temperature enhances erosion by a factor of 2.5–3. In contrast, for Mo, the simulated net erosion is ~ 3 times smaller than what experimental data indicate. The discrepancies can be attributed to the deviations of the background plasma profiles from the measured ones as well as to the applied models or approximations for the ion temperature, plasma potential, and sheath characteristics in ERO. In addition, the surrounding areas of the marker samples being covered with impurities and W from previous experiments may have considerably reduced the actual re-deposition of Mo. All the simulations predict a toroidal tail of re-deposited particles, downstream of the markers, but the particle density seems to be below the experimental detection threshold. The comparison between the 1 × 1 mm 2 and 5 × 5 mm 2 marker spots further reveal that re-deposition drops from >50% to <40% when decreasing the marker size. This indicates that small enough marker samples can be used for accurately determining gross erosion in ASDEX Upgrade.

Curved profiles machining of Ti6Al4V alloy through WEDM: investigations on geometrical errors

Great biocompatibility and superior mechanical properties of titanium alloys (Ti6Al4V) stimulate the use of this material frequently in biomedical, defence, and aeronautical industries. In these applications, the end parts generally have complex curved profiles. Through conventional means of machining, complex profiles with high dimensional accuracy are not easily achievable due to difficult-to-cut nature of Ti6Al4V. Wire Electric Discharge Machining (WEDM) is a promising alternative to cut the complex features like angular and curved features. In this research, convex and concave profiles are machined in Ti6Al4V through WEDM. The influence of four machining parameters, namely servo voltage, wire feed, pulse On- and Off-time, over the geometrical accuracies of convex and concave profiles along with corner radii have been comprehensively investigated. The L27 orthogonal array was taken as the design of the experiment, and the results are evaluated in terms of statistical (ANOVA and signal-to-noise ratio) and microscopic morphology by Scanning Electron Microscopy (SEM). Optimized combination of machining parameters are sought capable of resulting in minimum geometric deviations (0.250% overcut in convex and 0.236% undercut in concave profiles) and corner radii of 0.106 mm. Moreover, the SEM analysis has confirmed that the discharge energy and erosion phenomenon significantly affect the profile accuracy as well as the surface integrity. In addition to optimized parameters the provision of wire offset, ranging within 0.169–0.173 mm, can further mitigate the geometric deviations of the actual machined profiles from the designed geometries.

Aggregate Determination by Permeation Technique.

Permeation technique is used to study molecular aggregation in aqueous solutions including formation of cyclodextrin guest/host aggregates. Since only guest molecules, host molecules and guest/host aggregates that are smaller than the pore size of a given semipermeable membrane are able to permeate through the membrane, negative deviation of permeation profiles indicates formation of guest/host aggregates or self-aggregates. This chapter describes how the method is used to detect formation of nano-sized aggregates and to determine the critical aggregation concentration (cac) from permeation profiles of a guest molecule.