Circular Micro Research Articles

Exploring the efficiency of employing Fe3O4-MWCNT Nanofluids in a heat sink equipped with circular micro pin-fins

Exploring the efficiency of employing Fe3O4-MWCNT Nanofluids in a heat sink equipped with circular micro pin-fins

High temperature wear performance of in-situ forming textured Ni60/WC/h-BN composite coatings based on laser micro-cladding

In this study, electrohydrodynamic atomization technology and laser micro-cladding technology were used to design and prepare circular, square and bionic Nepenthe-shaped micro textures on the cemented carbide substrate. The mechanical properties of the prepared micro texture are significantly improved. The effects of different micro texture morphology on the tribological properties of the substrate in a wide temperature range were systematically studied. The results investigated that the bionic Nepenthe-shaped micro-texture showed the lowest friction coefficient at all temperatures, and when the temperature was 200 °C, the friction coefficient could be reduced to ∼0.14. The wear track analysis shows that the micro texture is the main way to reduce the friction coefficient at room temperature. When the temperature rises to 200 °C, the h-BN in the cladding layer will release at the friction interface to achieve the lubrication effect. When the temperature further increases, the cladding layer will soften and be smoothed, and the substrate will directly contact with counter ball, which will significantly increase the friction coefficient. By exploring the effect of micro texture morphology prepared by laser micro cladding technology on tribological properties, we can understand its applicability in different manufacturing tools.

Microscopic insights into the long-term ageing mechanism of asphalt in the hygrothermal environments

The humid, thermal, and oxidative environments cause the synergistic degradation of asphalt materials. To reveal the long-term ageing mechanism of asphalt in the hygrothermal environments, base asphalt (BA) and styrene-butadiene-styrene (SBS) modified asphalt (SMA) were selected to prepare the short-term, long-term, and hygrothermal-aged samples. Then the changes in micromorphology, molecular weight distribution, chemical compositions, and microstructures of each aged asphalt sample were characterized. The results indicate that the soaking duration is determined as 32 h for preparing the hygrothermal-aged asphalt sample. The moisture diffusion causes physical damage to asphalt, forming circular micro holes on the asphalt surface, which is the main reason to accelerate asphalt ageing. The ambient water and air can easily permeate into asphalt, further accelerating asphalt ageing. Additionally, the small and medium molecular components in the hygrothermal-aged BA are decreased, while the large molecular components become more. Meanwhile, the molecular weight distribution of SMA is relatively concentrated after hygrothermal ageing, and the SBS modifier is degraded from supermolecules to macromolecules. Further, no new chemical compositions are produced after hydrothermal ageing of BA and SMA. The hygrothermal ageing accelerates the oxidation of thioethers and unsaturated carbon bonds to convert into sulfoxide and carbonyl groups. Finally, the hygrothermal ageing destroys asphalt components, and the number of Catana phases on the BA surface is lowered. The Catana phases on the SMA surface were seriously damaged and almost disappeared in asphalt components. The surface elevations of BA and SMA are increased after hygrothermal ageing, but the surface roughness is decreased. This study provides the microscopic insight into the long-term ageing mechanism of asphalt in the hygrothermal environments.

Design and Analysis of 1x4 and 1x8 Circular Patch Microstrip Antenna Array for IWSN Application

A 1x4 and 1x8 circular micro strip patch antenna array operating at 2.4GHz are simulated for Industrial Wireless Sensor Network (IWSN) applications using CST studio suite and MATLAB based simulator software. The circular patch antenna designed on a FR4 substrate with dielectric constant of 4.4 and a substrate height of 1.6mm is fed using inset-fed technique. Several antenna characteristics such as return loss, radiation pattern, bandwidth, directivity, antenna gain, radiation efficiency isanalyzed. The compact size and higher directivity help to improve the network performance by alleviating contention, increasing communication range, and mitigating interference of the system. Hence, the advantages gained, make the system more useful for IWSN applications as achieved in this research

Circ_0022920 Maintains the Contractile Phenotype of Human Aortic Vascular Smooth Muscle Cells Via Sponging microRNA-650 and Promoting Transforming Growth Factor Beta Receptor 1 Expression in Angiotensin II-Induced Models for Aortic Dissection.

Background Abnormal regulation of vascular smooth muscle cells is regarded as the iconic pathological change of aortic dissection (AD). Herein, we aim to identify circ_0022920 as a crucial regulator in AD. Methods and Results Microarray analysis of circular RNAs, messenger RNAs, and micro RNAs in patients with AD was performed, and we identified that circ_0022920 was significantly downregulated in these patients. The Pearson correlation analysis uncovered the negative correlation between miR-650 and circ_0022920 or TGFβR1 (transforming growth factor beta receptor 1). Angiotensin II was used to treat human aortic vascular smooth muscle cells (HASMCs) and mice as models for AD. Hematoxylin and eosin and Masson's trichrome staining were used to analyze AD histopathology. Cell proliferation was analyzed with Cell Counting Kit-8 assay and EdU incorporation. Cell migration was assessed with transwell and wound healing assays. Enhanced circ_0022920 expression dramatically inhibited HASMC proliferation and migration and maintained contractile marker expression induced by angiotensin II, whereas miR-650 exerted opposite effects. MiR-650 was a target of circ_0022920. MiR-650 targeted IRF1 (interferon regulatory factor 1) and thus negatively regulated TGFβR1 expression to promote HASMC proliferation and migration and inhibit contractile marker expression. Circ_0022920 suppressed the progression of AD in vivo. Conclusions Circ_0022920 modulates the contractile phenotype of HASMCs via regulating the miR-650-IRF1-TGFβR1 axis in angiotensin II-induced models for AD, which provides potential therapeutic targets for AD.

Identification of circRNA-miRNA-mRNA regulatory network and its role in cardiac hypertrophy.

Hypertrophic cardiomyopathy (HCM) is a grave hazard to human health. Circular RNA (circRNAs) and micro RNA (miRNAs), which are competitive endogenous RNA, have been shown to play a critical role inHCM pathogenicity. However, to a great extent, the biological activities of ceRNA in HCM pathophysiology and prognosis remain to be investigated. By analyzing the expression files in the Gene Expression Comprehensive (GEO) database, differentially expressed (DE) circRNAs, miRNAs, and mRNAs in HCM were identified, and the target molecules of circRNAs and miRNAs were predicted. The intersection of the differentially expressed RNA molecules and the expected target was then calculated, and a ceRNA network was subsequently constructed using RNA molecules. Using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, the potential etiology was elucidated. qPCR was used to validate a portion of the hub gene using Angiotensin II to generate a cell hypertrophy model. Three large-scale HCM sample datasets were extracted from the GEO database. After crossing these molecules with their expected targets, the circRNA-miRNA-mRNA network had two DEcircRNAs, two DEmiRNAs, and thirty DEmRNAs, compared to normal tissues. Functional enrichment analysis of GO and KEGG demonstrated that many of the HCM pathways and mechanisms were associated with calcium channel release, which is also the primary focus of future research. The qPCR results revealed that circRNA, miRNA, and mRNA expression levels were different. They may include novel noninvasive indicators for the early screening and prognostic prediction of HCM. In this study, we hypothesized a circRNA-miRNA-mRNA regulation network that is closely related to the progression and clinical outcomes of HCM and may contain promising biomarkers and treatment targets for HCM.

Design and Optimization a Circular Shape Network Antenna Micro Strip for Some Application

Design and Optimization a Circular Shape Network Antenna Micro Strip for Some Application

Study of the Regimes of Diffusive Combustion of a Hydrogen Microjet

The paper presents the results of experimental studies of scenarios of diffusion combustion of a microjet of hydrogen flowing out of a cylindrical micronozzle with a diameter of 200 μm. The hydrogen microjet is ignited near the nozzle exit and at a distance. The experimental data are compared with the data previously obtained, and the results are expressed in dimensionless parameters (in terms of Reynolds numbers). It is established that the stabilization of flame during the outflow of a circular micro jet of hydrogen is associated with the presence of heating of the nozzle by a spherical flame region covering the nozzle section. The hysteresis of the diffusion combustion process of circular hydrogen microjets is shown depending on the ignition location of the microjet (near or far from the nozzle exit) and the change in the flow rate (growth or decrease).

Effect of Membrane Load on the Stability of an Electrostatically Actuated Initially Curved Circular Micro Plate

Abstract The effects of membrane load on the axisymmetric bistable behavior of circular curved micro plates are studied via an axisymmetric reduced order (RO) model, incorporating radial prestress. The model is based on Kirchhoff’s hypothesis and Föppl-von-Kármán’s kinematics. The model is first validated for a “mechanical” (displacement-independent) load, against an RO model with 20 degrees-of-freedom (DOF), a finite differences (FD) solution, and finally, a finite elements (FE) model, serving as the reference. All solutions implement the “Riks” continuation method to track unstable branches, which can swerve in a complex form due to the presence of higher buckling modes. A convergence study is carried out for the snap-through location and load, as well as for the critical elevation and prestress required for bistability. Based on the validated results of the mechanical analysis, the reliability of the model for predicting the effect of prestress on the plate behavior under nonlinear (displacement-dependent) electrostatic load is then investigated while using FD as the reference. The study furnishes an expended RO model for curved plates, which includes the effect of prestress. The resulting model can further be used to estimate the value of residual membrane load present in electrostatically actuated curved plates, as well as predict the threshold for bistability.

Miniaturized Antenna for IOT Application

Ansys platform-based HFSS simulator software is used to create a 4GHz circular micro strip patch antenna array. Applications including Bluetooth, the Internet of Things, and several WLANs can all benefit from it. The circular patch antenna, which is constructed on a FR4 substrate with a dielectric constant of 4.4 and a height of 1.6mm, is fed using edge feeding. The antenna is built using a 1.4mm thick FR-4 (lossy) substrate with a relative permittivity of 4.4 and a microstrip line feed. The chosen radius for the circular patch is 7.62mm. To lower the size and enhance the performance of the suggested antenna, a square slit 30mm by 30mm in size is etched onto the ground plane. The HFSS Simulation Program is employed in the antenna's design. Antenna characteristics such as return loss, radiation pattern, bandwidth, orientation, antenna gain and radiated efficiency are all studied.

Investigation of the Effect of ITO Size and Mesa Shape on the Optoelectronic Properties of GaN-Based Micro LEDs

In this paper, in order to explore the influence of indium tin oxide (ITO) size and mesa shape on the performance of GaN-based micro light emitting diodes (Micro LEDs) on sapphire substrates, Micro LEDs of different sizes with ITO area smaller than or equal to the light-emitting area were designed and fabricated. The experiment results show that when the ITO area of the Micro LED is equal to the area of the light-emitting area, its optoelectronic performance is significantly better than that of the Micro LEDs whose ITO area is smaller than the area of the light-emitting area. When the light-emitting area size is 40 μm, the wall-plug efficiency (WPE) of the two structures of Micro LEDs can differ by more than 50%. Based on above experiment results, this paper designed and fabricated Micro LEDs with different sizes of square and circular mesa with the same ITO area as the light-emitting area. The experimental results show that the WPE of the circular mesa Micro LED is slightly higher than that of the square mesa Micro LED at low current density. However, as the current density and chip size increase, the performance of the Micro LED with a square mesa is better.

Investigation on Flow Through Staggered Micro Pin Fin Arrays with Variable Longitudinal Spacings Using Micro-PIV

ABSTRACT In this study, the flow behavior of deionized water through the staggered circular micro pin fin arrays with three longitudinal spacings (S L = 2D, 3D and 4D) is investigated using flow visualization technology of micro particle image velocimetry (micro-PIV) in the range of Re = 100–800. The streamline distribution and velocity field in the three micro pin fin arrays are obtained. Experimental results indicate that the longitudinal spacing has considerable effect on both the extension of the wake region and velocity field around pin fins. The small longitudinal spacing hinders the extension of the wake region behind the pin fin and delays the vortex shedding. The micro pin fin array with S L = 2D provides maximum velocity span and transverse velocity, indicating intense local fluid mixing. The flow and heat transfer characteristics in the microchannel with a single circular micro pin fin are also studied. By comparison, the feature of the wake region in the micro pin fin array with a large longitudinal spacing is similar to that in the flow past a single micro pin fin. Moreover, vortex shedding occurs in the micro pin fin array at higher Reynolds number. The correlation between velocity field and temperature field around the pin fin is investigated. The belt zone with enhanced heat transfer around the pin fin is consistent with the distribution of fluid with high velocities. Vortex shedding can obviously enhance the heat transfer downstream of the micro pin fin.

Comparison between radiochromic film and Sun nuclear edge diode detector during the commissioning of small field size radiosurgery cones

Stereotactic Radiosurgery (SRS) is a procedure that uses ionizing radiation in a single fraction or few fractions to treat intracranial lesions. Usually, for these treatments, small photon fields, formed by circular collimators or micro multileaf collimators are used. The objective of the present work is to compare the measurements of the dose in depth (PDD), the off-axis ratio (OAR), and the output factor (OF) using Edge diode and radiochromic films and analyzing the agreement between the two detectors during these measures. In the gamma index analysis of the profiles, the minimum percentage reached was 98.3% of the points in the criterion 1% and 0.5 mm. The maximum percentage difference in the output factor was 2.79% for a cone 4 mm and 10FFF. In the gamma index analysis of the PDDs, the minimum percentage reached was 97% of the points in the criterion 1% and 1mm. The results show a good agreement between the edge detector and the film in small field measurements for radiosurgery.

Micro-particle image velocimetry study on hydrodynamic characteristics of in-line and staggered micro pin fin arrays

Detailed hydrodynamics in microchannels with in-line and staggered circular micro pin fin structures over Reynolds number ranging from 50 to 700 are experimentally studied with micro-particle image velocimetry. The velocity field, vortex structure and vorticity distribution is obtained and analyzed, and differences in flow behavior in the two arrangements are examined. The result indicates a delay in the onset of vortex shedding in micro pin fin arrays as compared to their macro scale counterpart due to the confinement effect of channel walls. Flow pattern in the in-line arrangement is featured by the microchannel-like main stream between the pin rows and the double vortex wake flow behind the pins, while flow in the staggered arrangement is characterized by the wavy main stream and a pair of accelerated flow streams on two sides of the pins. Vorticity bands along the sides of the wake region intensify with the Reynolds number, diffuse further downstream, but narrow in width. Visualization and data extraction results reveal that flow behavior in the staggered arrangement differs from that in the in-line arrangement in terms of a smaller area occupied by the low-velocity wake region and a more sufficient mixing of fluid.

Numerical simulation and experimental investigation on tribological performance of SiC surface with squamous groove micro texture

AbstractTo improve the tribological characteristics of the face seal, the squamous groove micro textures with different area proportion and the circular dimple micro texture were designed and manufactured. The disc‐disc friction and wear experiments and numerical simulation were carried out in oil lubrication. The pressure distribution, friction coefficient, fluid temperature and wear morphology are investigated. The study show that the friction coefficients of the micro textured and untextured samples decline with the increase of load, but first increase and then decrease with the rise of rotational speed. Micro textured samples could decline the friction coefficient effectively, and the asymmetric structure in the lubricant inflow and outflow region of the squamous groove micro texture makes it have better tribological performance. In addition, the micro texture can increase heat dissipation area, reduce heat production and collect wear debris, which could modify the lubricant temperature and wear morphology effectively.

Functional Interactions Between lncRNAs/circRNAs and miRNAs: Insights Into Rheumatoid Arthritis.

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases that affect synovitis, bone, cartilage, and joint. RA leads to bone and cartilage damage and extra-articular disorders. However, the pathogenesis of RA is still unclear, and the lack of effective early diagnosis and treatment causes severe disability, and ultimately, early death. Accumulating evidence revealed that the regulatory network that includes long non-coding RNAs (lncRNAs)/circular RNAs (circRNAs), micro RNAs (miRNAs), and messenger RNAs (mRNA) plays important roles in regulating the pathological and physiological processes in RA. lncRNAs/circRNAs act as the miRNA sponge and competitively bind to miRNA to regulate the expression mRNA in synovial tissue, FLS, and PBMC, participate in the regulation of proliferation, apoptosis, invasion, and inflammatory response. Thereby providing new strategies for its diagnosis and treatment. In this review, we comprehensively summarized the regulatory mechanisms of lncRNA/circRNA-miRNA-mRNA network and the potential roles of non-coding RNAs as biomarkers and therapeutic targets for the diagnosis and treatment of RA.

Sustainable Circular Micro Index for Evaluating Virtual Substitution Using Machine Learning with the Path Planning Problem as a Case Study

Due to the problems resulting from the COVID-19 pandemic, for example, semiconductor supply shortages impacting the technology industry, micro-, small-, and medium-sized enterprises have been affected because the profitability of their business models depends on market stability. Therefore, it is essential to propose alternatives to mitigate the various consequences, such as the high costs. One attractive alternative is to replace the physical elements using resource-limited devices powered by machine learning. Novel features can improve the embedded devices’ (such as old smartphones) ability to perceive an environment and be incorporated in a circular model. However, it is essential to measure the impact of substituting the physical elements employing an approach of a sustainable circular economy. For this reason, this paper proposes a sustainable circular index to measure the impact of the substitution of a physical element by virtualization. The index is composed of five dimensions: economic, social, environmental, circular, and performance. In order to describe this index, a case study was employed to measure the path-planning generator for micro aerial vehicles developed using virtual simulation using machine-learning methods. The proposed index allows considering virtualization to extend the life cycle of devices with limited resources based on suggested criteria. Thus, a smartphone and the Jetson nano board were analyzed as replacements of specialized sensors in controlled environments.

A study and comparison of the modes of diffusion combustion of hydrogen and methane at their outflow from the annular nozzle together with the flow of supplied air from the coaxially located circular nozzle

The article presents qualitative data on the study of the process of diffusion combustion during the outflow of a gas jet from a nozzle apparatus with a certain arrangement of nozzles. The nozzle apparatus is a round nozzle with a straight channel and a coaxially located annular slot. In the experiments, hydrogen or methane was supplied through an annular slot, and the air was supplied through a central circular micro nozzle. The main features of the diffusion combustion of hydrogen and methane during the outflow from the nozzle apparatus are revealed and a qualitative comparison of the processes is carried out. In both cases, at the initial stage, laminar combustion is observed near the nozzle exit and a breakthrough of the flame front occurs with the release of an incombustible mixture of combustible gas and air. At a high flow rate, the flame separates from the nozzle exit. The fundamental difference is that hydrogen exhibits significantly better combustion stabilization characteristics at the nozzle exit.

Performance improvement of turning operation during processing of AISI 304 with novel textured tools under minimum quantity lubrication using hybrid optimization technique

ABSTRACT Manufacturing cost and productivity in machining systems can be significantly affected by the optimized input sources. Further, metal cutting industries have shown curiosity toward surface textured tools due to gain in productivity. In this context, new textured tools were developed and machinability studies were carried out on AISI 304 material under eco-friendly technique namely Minimum Quantity Lubrication (MQL) with so developed tools. The novel textured tools were fabricated by making circular micro pit holes on the rake face of the tungsten carbide tool using laser technology. In this work, a new weighted gray relation analysis (WGRA) integrated Jaya algorithm is proposed to determine the best cutting parameters. From the result, it is found that 54%, 7% respective reduction in surface roughness (Ra) and tool wear (Vb) and 27% increment in material removal rate (MRR) at the optimum conditions determined by the proposed optimization technique. It is concluded that the proposed work meets the environmental sustainability requirements and improved the turning process performance.

Investigating the thermal efficiency and pressure drop of a nanofluid within a micro heat sink with a new circular design used to cool electronic equipment

The present study numerically simulates a new circular micro heat sink (HS) used to cool electronic equipment (i.e., CPU). The HS contained Al2O3-water nanofluid (NF) at the concentration of 0–1%. The HS had a diameter and a thickness of 7.6 and 0.5 mm, respectively. It included two separate inlets with a 6 mm-diameter middle section subjected to a fixed heat flux of 100 W/cm2. NF flows were employed to cool the HS at the Reynolds numbers of 500–1500. The FVM-based SIMPLE algorithm was developed to obtain the entropy generation, thermal efficiency, and pressure drop. The results revealed that a rise in Re number and NF concentration enhanced Nu and head loss, while reduced the maximum and average temperatures of the electronic device. The best figure of merit (FOM) of the HS was found to be 1.12. A raise in the fluid velocity and NF concentration increased the pumping power but reduced thermal resistance.