Bumpy Surface Research Articles

Effect of temperature on the stability and performance of III-nitride HEMT magnetic field sensors

The study aimed to investigate the underlying physics limiting the temperature stability and performance of non-surface passivated Al0.34Ga0.66N/GaN Hall effect sensors, including contacts, under atmospheric conditions. The results obtained from analyzing the microstructural evolution in the Al0.34Ga0.66N/GaN Hall sensor heterostructure were found to correlate with the electrical performance of the Hall effect sensor. High-resolution x-ray photoelectron spectroscopy studies revealed the signature of surface oxidation in the GaN cap layer, as well as a slight out-diffusion of “Al” from the AlGaN barrier layer. To prevent the formation of a bumpy surface morphology at the Ohmic contact, we investigated the impact of “Pt” top Ohmic contacts. The application of a top “Pt” contact stack resulted in a smooth Ohmic contact surface and provided evidence that the bumpy surface morphology in Au-based Ohmic contacts is due to the formation of an Al-Au viscous alloy during rapid thermal annealing. In the early stages of thermal aging, the small drop in contact resistivity stabilized with subsequent thermal aging past the initial 550 h at 200 °C. The outcome is that the Al0.34Ga0.66N/GaN Hall effect sensors, even without surface passivation, exhibited a stable response to applied magnetic fields with no sign of significant degradation after 2800 h of thermal aging at 200 °C under atmospheric conditions. This observed stability in the Hall sensor without surface passivation can be attributed to a self-imposed surface oxidation of the cap layer during the early stages of aging, which serves as a protective layer for the device during subsequent extended periods of thermal aging at 200 °C.

Demonstrating a Quartz Crystal Microbalance with Dissipation (QCMD) to Enhance the Monitoring and Mechanistic Understanding of Iron Carbonate Crystalline Films.

This paper reports the real time monitoring of siderite deposition, on both Au- and Fe-coated surfaces, using the changes in frequency and dissipation of quartz crystal microbalance with dissipation (QCMD). In an iron chloride solution saturated with carbon dioxide, buffered with sodium bicarbonate to pH 6.8, roughly spherical particles of siderite formed within 15 min, which subsequently deposited on the QCMD crystal surface. Imaging of the surface showed a layer formed from particles ca. < 0.5 μm in diameter. Larger particles are clearly deposited on top of the lower layer; these larger particles are >1 μm in diameter. Monitoring of the frequency clearly differentiates the formation of the lower layer from the larger crystals deposited on top at later times. The elastic moduli calculated from QCMD data showed a progressive dissipation increase; the modeling of the solid-liquid interface using a flat approximation resulted in a poor estimation of elastic and storage moduli. Rather, the impedance modeled as a viscoelastic layer in contact with a semi-infinite liquid, where a random bumpy surface with a Gaussian correlator is used, is much more accurate in determining the elastic and storage moduli as losses from the uneven interface are considered. A further step considers that the film is in fact a composite consisting of hard spherical particles of siderite with water in the vacant spaces. This is treated by considering the individual contributions of the phases to the losses measured, thereby further improving the accuracy of the description of the film and the QCMD data. Collectively, this work presents a new framework for the use of QCMD, paired with traditional approaches, to enhance the understanding of crystal deposition and film formation as well as quantify the often evolving mechanical properties.

FEATURES OF ESTROGEN AND PROGESTERONE RECEPTOR EXPRESSION IN MENINGIOMAS DEPENDING ON GENDER

Introduction. Meningiomas are non-malignant brain or spinal cord neoplasms originating from meningeal cells. The etiology of meningiomas remains insufficiently studied due to the subclinical course and relatively low incidence. Because meningiomas affect women more than twice as often as men, and there are recorded cases of the disease in pregnant women, it is advisable to investigate the role of female sex hormones in the development of this disease. Objective. Our work aimed to study the features of the expression of estrogen and progesterone receptors in meningioma tissue depending on the gender of the patients. Methods and matreials. A total of 50 samples were examined, of which 25 samples were from female patients (group W) and 25 from male patients (group M). The average age of patients in group W was 60.92±1.84 years, and group M was 59.88±3.39 years. Regardless of the equivalent indicators of average age, it is worth noting that the age of female patients varied 42 to 79 years and of male patients – 24 to 88 years. We examined the samples macroscopically, histologically and immunohistochemically (antibodies against estrogen and progesterone receptors). Results. When examined macroscopically, the meningioma had a characteristic spherical or plaque-like shape, grey colour, somewhat bumpy surface, moderate density, and fibrous structure on cross-section. During the histological examination, most samples in both groups were assigned to psammomatous or meningothelial histological subtypes, the characteristic histological patterns of which were concentric structures of flattened tumour cells and psammoma bodies. Conclusions. Immunohistochemical examination of meningioma tissue with antibodies against estrogen (ER) and progesterone (PR) receptors showed their more significant presence in samples of female patients compared to samples of male patients (p&lt;0.001), which confirms the critical role of female sex hormones in etiology and pathogenesis meningioma.

Design and Evaluation of Field Segmentation, Path Generation and Sequential Point Tracking Algorithms for Agricultural Mobile Robots

Highlights Field segmentation, path generation, and sequential point tracking algorithms were designed for agricultural mobile robots. An optimized field segmentation plan and operation path could be generated for the robot. The sequential point tracking algorithm could guide the robot to a series of target points. The algorithms were tested in simulation calculations and practical experiments. Abstract. As agricultural production becomes increasingly intelligent, operations by autonomous mobile robots become an inevitable trend. For some operations, such as in-field soil sampling, agricultural robots need to track a series of target points in the field. In this work, a field segmentation algorithm, a path generation algorithm, and a sequential point tracking algorithm were designed and evaluated. The field segmentation and operation path generation algorithms, which took, respectively, the total lost area of the field and the total turning angle of the robot as optimization objectives, aimed to provide an efficient operation plan for the robot to follow. The sequential point tracking algorithm was designed for the robot to realize automatic tracking of the planned target points following a desired sequence. The algorithms were tested by simulation calculations using the boundary coordinates of two test fields and field experiments based on a small four-wheeled mobile robot. Field results of the straight-path, multi-target point tracking experiment showed that the designed steering angle and velocity control laws could accurately guide the robot from a start point to a series of target points when the robot was running on a concrete surface. The absolute distance errors of the robot with respect to the targets were smaller than 0.03 m. To test the robot’s tracking performance on different surface conditions, two whole-field, continuous point tracking experiments were performed. The general effectiveness of the sequential point tracking algorithm was validated. When the robot was running on hard surface conditions (concrete and grass), the tracking errors were between 0.014 m and 0.074 m. When the robot was running on a soft and bumpy soil surface, the tracking accuracy degraded to submeter level due to the limitation of small-size wheels. The average, RMS, and maximum errors were 0.774 m, 0.775 m, and 0.798 m, respectively. However, the feasibility of the sequential control algorithm was not influenced. The designed algorithms could be potentially utilized in the development of robotic systems for in-field site-specific operations. Keywords: Agricultural mobile robot, Control sequence, Field segmentation, Operation path generation, Point tracking.

Features and Sustainable Design of Firefighting Safety Footwear for Fire Extinguishing and Rescue Operations

Firefighters are regularly exposed to risk of injuries as a result of their intervention activities connected with hazards from fire and explosion, as well as due to carrying heavy personal working equipment and injured victims from accidents. Another hazardous factor is working under unfavorable weather conditions and also moving on slippery or bumpy surfaces. Employers provide personal protective work equipment to employees if a hazard cannot be eliminated or reduced by technical means, such as means of collective protection or methods and forms of work organization. Personal Protective Equipment (PPE) should provide effective protection against existing and foreseeable hazards and should not in itself create a greater risk. It should be adapted to the existing and predictable working conditions and working environment at the work site, meet the criteria of ergonomics and the health condition of an employee as well as be suitable and adapted to the wearer’s body so that, if possible, there is no risk of harm to the employee’s health. The aim of this Special Issue is to explore the limits of sustainable implementation of additive technologies within current manufacturing practices and current requirements for personal protective equipment for firefighters. More precisely, the goal of this special article is to show new ideas in firefighting footwear such as a quick donning and doffing system as well as various other improvements and sustainable design of firefighting footwear. The aim is to present new ideas and concepts, the latest advances, and technical tools supporting the sustainable use of protective firefighting footwear. Special attention will be paid to standards that ensure the highest standard and quality.

Surface confinement of vertically aligned liquid crystals between flexible silver nanoparticles hybridized polyimide thin layers

Alignment of liquid crystals (LCs) has emerged as an essentially fundamental approach for exploring the electro-optical performance and fabricating novel LC devices. Growing evidence suggests that the surface wettability of the alignment layer plays a key role in tuning the tilt angles of LCs. In this work, silver (Ag) nanoparticles (d ≤ 100 nm) are blended in polyimide (PI) by a wide range of concentration from 0.1% to 1.0% to tune surface wettability and align LCs. Ag nanoparticles agglomerate and result in a bumpy surface topology and somewhat reduce the transparency of hybrid thin layer to 85.1% by 1.0% doping because of their shielding effect. Nevertheless, Ag nanoparticle agglomerates change the thickness of hybrid thin layers less, and the hybrid thin layers are ∼96 nm thick like a pure PI thin layer. LCs are vertically aligned on hybrid thin layers after rubbing. Benefit from the declined anchoring energy and the outstanding surface plasmon polariton (SPP) of Ag nanoparticles, the external electric field to switch LCs is substantial boosted, and hence remarkably diminish the operating voltage and likewise notably shorten the response time. In particular, LCs that vertically aligned between PI hybrid alignment layers by 0.5% doping could be electrically switched to become planner at 3.38 V and go back to their original vertical alignment state within 73.21 ms. Ag nanoparticles agglomerates in hybrid thin layers also fairly hinder the drift of LCs when cells are mechanically bent with various radii. The hybrid alignment layers cell that blended with 0.5% Ag nanoparticles could be bent under 1500 mm without any new evident light leakages and fluctuating electro-optical characteristics. These results indicate the promising applications of PI hybrid thin layers blended with Ag nanoparticles for flexible LC devices.

A new design of seat suspension using different models of negative stiffness structure

Three models of seat suspension using the negative stiffness structure including steel springs (SS), roller springs (RS), and tuned mass damper (TMD) are proposed and studied to improve the driver's seat ride comfort. Based on the dynamic models of the SS, RS, and TMD, their isolation efficiency and driver’s ride comfort are evaluated via two indexes of the root mean square displacement and acceleration of the seat (zws and aws) under two excitations of the random road surface and bumpy road surface. The results show that under the random road surface, the zws and aws with the seat's RS are reduced by 10.31 % and 20.32 % in comparison with the seat’s SS; whereas the zws and aws with the seat's TMD are smaller than that of the seat's RS by 19.15 % and 26.13 %; and the seat’s SS by 27.49 % and 41.15 %, respectively. Besides, the seat's displacement and acceleration responses with the seat’s TMD are also lower than that of both the SS and RS under the bumpy road surface. Therefore, the structure of the TMD should be designed and added to the seat suspension to enhance the driver’s seat ride comfort.

Manipulation of bumpy surface cylinders for flow control and heat transfer improvement

The present work aims at investigating laminar flow effects over bumped-surface circular cylinders at Reynolds number ≤ 200. Three bumpy cylinder surfaces are considered and studied, comprising square, triangular, and dimple surface shapes. The bumpy surfaces are placed on the upper surface of the cylinder and arranged between 0° and 90° from the front stagnation point of the cylinder. These angles include θ = 0○, 45○, and 90○. The flow characteristics, such as the lift and drag coefficients, as well as the Strouhal and Nusselt numbers, are evaluated. For all three examined bump shapes, it is demonstrated that when θ ≤ 45°, the amplitude of the drag coefficient is smaller than larger angles. It is also found that at θ = 90°, the magnitude of the drag coefficient is about 40% larger than test cases with θ ≤ 45°. It is found that the Nusselt number is dependent on the location of the bump on the leading surface of the cylinder. The critical angle of the bump's location is identified and introduced, which is θcm = 45°. While the minimum Nusselt number is obtained once the bump is located at θcm = 45°, the maximum Nusselt number is assessed at θ = 90° with approximately a 12% increment.

Cytotoxic effect and mechanism of nano-sized polystyrene degraded by Rhodococcus ruber C208

Microbial biodegradation has emerged as a promising solution for environmental issues involving petrochemical-based plastics. However, the altered physicochemical properties of nanoplastics (NPs) induced by biodegradation and their effects on cellular behavior are unclear. Here, we generated NPs (bPS(r)s) using polystyrene (PS) and Rhodococcus ruber C208 (R. ruber C208) to assess changes in physicochemical properties and cytotoxic effects of bPS(r)s in keratinocytes. Compared with PS NPs, the biodegradation of PS using R. ruber C208 induced a decrease in particle size (408.2 to 324.2 nm), extant extracellular polymeric substances, changes in shape and functional groups, surface charge alteration, and enhancement of particle dispersion. Especially, irregular and bumpy surface with disintegration of PS structure was examined in bPS(r). The resulting physicochemical changes in bPS(r)s significantly increased cytotoxicity. This led to three times higher intracellular reactive oxygen species generation in keratinocytes (SOD2 gene expression), and reduced cell proliferation to about 83% of that of PS NPs at the concentration of 1.5 μg/mL. Keratinocytes after bPS(r) treatment also showed upregulated inflammation-related gene (IL-6 and TNF-α) expression compared to that in PS NPs. Overall, our findings suggest new features and methods for future studies on the effect of biodegradable NPs.

Effects of Physical and Mechanical Properties of Soft Soil on Subgrades Performances in Lubuk Bayas Village, Serdang Bedagai Regency

Generally, the existence of soft soil in Indonesia will be a problem in the construction of highway construction. One factor that influences and needs to be known in road construction is the characteristics of the subgrade where the pavement construction will be placed on it. Poor soil characteristics can cause bumpy road surfaces, cracks, or other road damage. Therefore, before carrying out a soil improvement, it is necessary to know its characteristics through the physical and mechanical properties of the subgrade. This research was conducted in Lubuk Bayas Village, Serdang Bedagai Regency, North Sumatra Province. Tests of physical properties in this study include sieve analysis, water content, specific gravity, plasticity limit test, and liquid limit test. The soil shear strength test and California Bearing Ratio (CBR) test were carried out to test the mechanical properties using a Dynamic Cone Penetrometer (DCP). From the results of testing the physical properties of the soil, it was found that Samples 1, 2, and 3 were fine-grained soils with the percentage of soil passing the No.200 sieve greater than 50%. The USCS classification system shows that samples 1 and 2 of the soil are in the Lean Clay (CL) group, while sample 3 is in the Fat Clay (CH) group. Samples 1, 2, and 3 include soils with high plasticity because the PI value is >17. The results of testing the mechanical properties of the soil Sample 1 obtained the value of c = 0.1299 kg/cm2 and Ø = 13.2°, in Sample 2 obtained the value of c = 0.1075 kg/cm2 and the value of Ø = 11.2° and in Sample 3 obtained the value of c = 0.1275 kg/cm2 and the value of Ø = 11.9°. DCP testing on samples 1, 2 and 3 obtained CBR values of 5.35%, 4.73% and 3.15%. From the CBR results, it can be seen that the soil in this location has a low soil bearing capacity, so if it is to be used as a subgrade layer, it will be necessary to repair the soil first so that structural damage does not occur in the future. Soil improvement can be made by stabilizing the soil using natural materials to maintain environmental sustainability. Natural materials that can be used include sand with certain gradations, stone ash, palm shell ash, and various other natural materials.

MRI Semiotics Features and Difficulties of Differential Diagnosis of Hepatic Metastases from Neuroendocrine Tumours

Relevance: Isolated bilobar multifocal hepatic lesion is consider to be the most common metastatic neuroendocrine tumor(NET) growth pattern. Underestimation of the metastatic burden in the NET patients at the initial diagnosis frequently occurs, thus leading to a high postoperative recurrence rate (more than 60 % of cases within 5 years).Purpose: To identify the MRI-hallmarks of liver metastatic NETs and to present the most difficult diagnostic cases.Material and methods: 103 patients with histology confirmed liver metastatic NET were enrolled in the study. All patients underwent abdominal contrast-enhanced (CE) MRI. A total of 241 lesions were assessed. Quantitative indicators of signal intensity (SI) on native and post-contrast T1-weighted images (WI) were measured in metastases. Additionally, the shape, contours, surface of metastases, SI on native images, characteristics of CE, the presence of hemoglobin degradation products and the boundary levels in the structure of metastases were qualitatively assessed.Results: Metastatic liver disease in NET is mostly multifocal: 78 (75.7 %) patients had 5 or more lesions. Metastases were round in 53.5 % of cases, oval in 17.5 % of cases, irregular in 29 % of cases. In 61 % of cases, the contours of the lesions were clear, in 39 % — indistinct. Smooth and bumpy surface of metastases was determined in 31.5 % and 68.5 % of cases, respectively. The presence of hemoglobin degradation products in the structure of metastases was determined in 26.2 % of patients, the formation of the boundary levels — in 8.1 % of patients. Most of the lesions had a hyperintense signal on T2-WI with and without FS and a hypointense signal on native T1-WI. The proportions of actively, moderately and poorly MR contrast agent (MRCA) enhanced lesions were 30.8, 32.6 and 36.6 %, in the arterial phase and 16.3, 55.4 and 28.3 % in the venous phase, respectively. The apparent diffusion coefficient (ADC) values varied significantly. In some cases, small metastatic NET were visualized only in the arterial phase of CE and were not detected on other MRI sequences, thus requiring differentiation from other hepatic hypervascular lesions.Conclusion. The MRI semiotics features of hepatic metastases from NETs is described. Small flesions of active accumulation of MRCA in the arterial phase in the presence of primary NET must be differentiated from metastatic lesions.

EFFECT OF PREPARATION TEMPERATURE ON ETHYLCELLULOSE MICROSPHERE PROPERTIES PREPARED BY OIL-IN-OIL EMULSION SOLVENT EVAPORATION PROCESS

The present study aims to formulate ethylcellulose microspheres using the oil-in-oil emulsion solvent evaporation method and judge the outcome of processing temperature on their features. The effects of the evaporation rate of the solvent on the particle properties and drug release characteristics of the microspheres were studied. Here, microspheres were prepared at different processing temperatues, viz., 10 0 C, 25 0 C, and 40 0 C, and their impact on the various characteristics of microspheres like surface topography, micrometrics, yield percent, encapsulation efficiency, in vitro dissolution, Fourier-transform infrared spectroscopy (FTIR) and release kinetics were elaborately studied. The FTIR study revealed that processing temperature did not affect drug-polymer compatibility. The study observed that the processing temperature had a great influence on the various characteristics of the prepared microsphere. It was observed from sieve analysis that the mean particle size of the microsphere increased with an increase in processing temperature, and the SEM study also corroborated the same result. SEM photographs showed processing at a higher temperature resulted in particles with a smooth surface, in contrast to a lower processing temperature that forms a bumpy surface. Furthermore, a higher temperature favoured formulation with a higher entrapment efficiency (94.42 ± 0.9 %) as compared to a lower temperature (85.2 ± 0.72 %). For a noteworthy timeframe, indinavir sulfate frames a solid solution in the ethylcellulose matrix and proceeds with the amorphous state. The results of an in vitro drug dissolution study showed that microspheres formulated at a higher temperature had a more sustaining effect as compared to those formulated at a lower temperature, which may have resulted due to their higher mean particle size. Using the Korsemeyer Peppas power law, it was found that the way drugs are released is controlled by diffusion.

Giant nodular basal cell skin cancer

The article presents clinical case report of primary giant nodular basal cell skin cancer in two patients at the age of 64 and 68 years and with disease duration of 20 and 15 years respectively. Psychological status of fear and anxiety are considered the main reasons for the late health encounter.&#x0D; The clinical picture of the case report was characterized by a slow long-term asymptomatic growth of solitary tumor-like mushroom-shaped nodes of stagnant pink color with a bumpy surface, densely elastic consistency, adherent to underlying soft tissues and sized 9.5 7.0 cm and 5.0 9.0 cm respectively. Giant basaliomas were located on the scalp in a woman and on the trunk skin in a man. The clinical tumors features are corresponded to those of a large conglomerated basal cell skin cancer. The article also presents a description of the clinical and dermatoscopic picture of giant nodular basaliomas.&#x0D; The patients underwent curative surgical excision of tumors with pathomorphological examination of the postoperative material. The histological picture of giant basal cell carcinoma in both cases is represented by tumors of a complex structure, namely a solid adenoid type with invasion into the reticular dermis and subcutaneous fat. The low biological potential of giant nodular basaliomas has been established.

Speed Control of Mobile Robots Using Vibration Stimuli from Bumpy Road Surface

Speed bumps and rumble strips have been introduced into the traffic infrastructure to improve traffic safety. When a vehicle travels on a road where speed bumps and rumble strips are installed, vibration stimuli are transmitted to the driver to encourage control of the speed and position of the vehicle. In this letter, speed bumps are applied to an automated driving system. More precisely, this letter considers the speed control of a mobile robot using vibration stimuli from bumpy road surfaces. We formulated a design problem for a speed control law for a mobile robot and proposed a controller that can adjust the speed according to road surface geometry. The performance of the proposed method was verified via simulation using Unity.

Conjunctival rhinosporidiosis

Rhinosporidiosis is a rare ocular infection and a chronic granulomatous disease caused by Rhinosporidium seeberi. The disease is endemic in India and Sri Lanka but has been known to occur even in colder regions of North America and Eastern Europe. It is most commonly seen as a soft polypoidal pedunculated mass affecting mucus membranes of the nose, pharynx, and conjunctiva. We present a case of a 23 years male who presented with a flat, pedunculated, highly congested mass with a bumpy surface attached at the inferior border of the tarsal conjunctiva. It was initially suspected to be an epithelialized impacted foreign body but when completely excised and sent for histopathological examination revealed rhinosporidiosis. Diagnosis is based solely on microscopic features. Even though a rare clinical entity, it should be borne as a differential in case of any pedunculated conjunctival mass.

Silicon wafer as a feasible candidate for tribological characterization of thin coatings under high contact stress?

Silicon (Si) wafer is generally used as the substrate for structural analysis and residual stress measurement of thin coatings. A few studies can be found for mechanical and tribological characterization wherein Hertzian contact stress never exceeded 1 GPa. Si, being single crystal, pure, and having low surface roughness (Ra) is an ideal potential candidate for thin coating analysis. However, Si wafer breaks immediately under higher contact stress. The current study aims to push the contact stress limit to test thin coatings on Si wafer especially for friction and wear testing. To serve the purpose, different bias DLC coatings (−120 V, −80 V, −40 V, Zero V, +40 V, +80 V, +120 V) were deposited on Si wafer employing closed field unbalanced magnetron sputtering (CFUMS) system. Using conveniently available experimental approach, Hertzian contact stress in tribological tests has been pushed up to 2.6 GPa successfully on DLC coated Si wafer. Thus, it is feasible to test thin coatings on Si wafer at high contact stress which will provide useful and consistent friction and wear data such that further test using the steel substrate will be reduced by a significant margin. A thorough mechanical, tribological and structural (Raman) analysis is presented. It was found that −120 V possessed the highest hardness (H: 17.6 GPa), modulus (E: 184 GPa) and residual stress (4.5 GPa). The same coating produced the lowest sp2/sp3 ratio, wear rate using contact stress (0.092 × 10−13 mm4/N) and wear/friction energy (0.071 × 10−13 mm3/J2) in comparison to other coatings used in the study. Counter body analysis for −120 V shows the minimum scratch area depicting friction between transfer film and DLC hence the lowest coefficient of friction (0.061) was obtained. Moreover, surface topography is explained with the aid of atomic force microscope (AFM) images and surface roughness (Ra) data. AFM revealed craters and bumpy like surfaces for positive and negative biased samples respectively.

As-Continuous-As-Possible Extrusion-Based Fabrication of Surface Models

In this study, we propose a computational framework for optimizing the continuity of the toolpath in fabricating surface models on an extrusion-based 3D printer. Toolpath continuity is a critical issue that influences both the quality and the efficiency of extrusion-based fabrication. Transfer moves lead to rough and bumpy surfaces, where this phenomenon worsens for materials with large viscosity, like clay. The effects of continuity on the surface models are even more severe in terms of the quality of the surface and the stability of the model. We introduce a criterion called the one–path patch (OPP) to represent a patch on the surface of the shell that can be traversed along one path by considering the constraints on fabrication. We study the properties of the OPPs and their merging operations to propose a bottom-up OPP merging procedure to decompose the given shell surface into a minimal number of OPPs, and to generate the “as-continuous-as-possible” (ACAP) toolpath. Furthermore, we augment the path planning algorithm with a curved-layer printing scheme that reduces staircase defects and improves the continuity of the toolpath by connecting multiple segments. We evaluated the ACAP algorithm on ceramic and thermoplastic materials, and the results showed that it improves the fabrication of surface models in terms of both efficiency and surface quality.

Particle force-based density segregation theory for multi-component granular mixtures in a periodic chute flow

Density segregation of multi-component granular mixtures in a dense, gravity-driven flow over a rough and bumpy periodic chute surface is studied using theory and simulations. An existing theoretical model for predicting the steady-state concentration field of each species in a binary mixture using the forces acting on the particles is generalised for multi-component mixtures in this work. In addition, the rheological model for binary mixtures is also extended to multi-component mixtures. In contrast to the percolation velocity-based empirical segregation models that do not account for the rheology and need prior knowledge of the velocity field, the present approach accounts for the inter-coupling of rheology with segregation. The momentum balance equations are solved, along with the mixture rheological model as well as the multi-component density segregation model, to obtain concentration fields using an iterative numerical method. The theoretical predictions are compared with discrete element method (DEM) simulations for ternary, quaternary and quinary granular mixtures differing in density. The steady-state profiles for the concentration of different species as well as other flow properties predicted from the theory are in excellent agreement with the DEM simulation results for a variety of compositions over a range of inclination angles for different density ratios. Through this work, we take the first essential step towards proposing a generalised particle force-based segregation theory for multi-component mixtures differing in size and/or density.

Changes in CT-Based Morphological Features of the Kidney with Declining Glomerular Filtration Rate in Chronic Kidney Disease.

Chronic kidney disease (CKD) progression involves morphological changes in the kidney, such as decreased length and thickness, with associated histopathological alterations. However, the relationship between morphological changes in the kidneys and glomerular filtration rate (GFR) has not been quantitatively and comprehensively evaluated. We evaluated the three-dimensional size and shape of the kidney using computed tomography (CT)-derived features in relation to kidney function. We included 257 patients aged ≥18 years who underwent non-contrast abdominal CT at the Inha University Hospital. The features were quantified using predefined algorithms in the pyRadiomics package after kidney segmentation. All features, except for flatness, significantly correlated with estimated GFR (eGFR). The surface-area-to-volume ratio (SVR) showed the strongest negative correlation (r = -0.75, p < 0.0001). Kidney size features, such as volume and diameter, showed moderate to high positive correlations; other morphological features showed low to moderate correlations. The calculated area under the receiver operating characteristic (ROC) curve (AUC) for different features ranged from 0.51 (for elongation) to 0.86 (for SVR) for different eGFR thresholds. Diabetes patients had weaker correlations between the studied features and eGFR and showed less bumpy surfaces in three-dimensional visualization. We identified alterations in the CKD kidney based on various three-dimensional shape and size features, with their potential diagnostic value.

INVESTIGATION OF TRANSIENT RESISTANCE AND ELECTRICAL EROSION OF SERIAL CONTACT PARTS RELAY PKL - 2204

In this study, the processes of the occurrence of an electric arc and its duration on the contact details of the PKL-2204 series relay are considered in detail. The patterns of changes in electrical erosion, which is a function of current strength and the number of switchings, were also studied. A detailed analysis of the process of opening the contact details was carried out based on the voltage oscillogram. Studies have shown that this process can be considered in three main stages. The first stage is marked by the separation of the contact parts, and at the very moment of the break of the working surfaces, there is a sharp jump in voltage from 45 mV to 13.5 V, accompanied by the formation of an electric arc. The second stage, lasting about 3.5 ms, is characterized by the weakening of the current to zero, and the arc is completely extinguished on the oscillogram. The third stage is marked by the appearance of a voltage peak on the oscillogram, which occurs when the arc is extinguished and is caused by the inductance L=240 mH. This analysis helps to better understand the process of contact opening and may have practical applications in the field of electrical engineering and electronics. Analysis of the results of our research indicates the presence of metals that have high resistance to erosion, regardless of their role as an anode or cathode. Among these metals, we can note nickel, copper, niobium, molybdenum, silver, and others, which show resistance to erosion even when the polarity changes, that is, they are erosion-resistant both at the anode and at the cathode. In particular, among such metals it is worth noting silver, molybdenum and niobium, which demonstrate extraordinary resistance to erosion in various conditions. These results may have important implications for the development of erosion-resistant materials for electronic devices and other applications. On the basis of the conducted research, it was found that the electroerosion resistance of contact parts made of СрН-10 material depends on several factors, including the current strength, the duration of arc burning, the number of commutations, and the physical and mechanical properties of the contact material. Research into the microstructure of the material during the current switching process revealed thermal, mechanical, and fatigue failure. During this process, the low-melting component of the cathode material melts and intensively evaporates, which leads to the formation of a dispersed and bumpy surface. The working surface of the anode is covered with finely dispersed silver particles, which are transferred from the cathode through the gaseous or liquid phase. The analysis of the spectra of the surface layers indicates a significant occurrence of nickel on the working surface of the cathode, which confirms the priority of evaporation of silver from the surface of the contact part during current switching. The study of the effect of chemically active reagents on transient resistance showed that in humid air with a high content of ammonia, hydrogen sulfide, sulfur dioxide, and carbon dioxide, the transient resistance of contact parts increases by 5-7 times.