Integrating PointNet-Based Model and Machine Learning Algorithms for Classification of Rupture Status of IAs.

BACKGROUND: The rupture of intracranial aneurysms (IAs) would result in subarachnoid hemorrhage with high mortality and disability. Predicting the risk of IAs rupture remains a challenge. METHODS: This paper proposed an effective method for classifying IAs rupture status by integrating a PointNet-based model and machine learning algorithms. First, medical image segmentation and reconstruction algorithms were applied to 3D Digital Subtraction Angiography (DSA) imaging data to construct three-dimensional IAs geometric models. Geometrical parameters of IAs were then acquired using Geomagic, followed by the computation of hemodynamic clouds and hemodynamic parameters using Computational Fluid Dynamics (CFD). A PointNet-based model was developed to extract different dimensional hemodynamic cloud features. Finally, five types of machine learning algorithms were applied on geometrical parameters, hemodynamic parameters, and hemodynamic cloud features to classify and recognize IAs rupture status. The classification performance of different dimensional hemodynamic cloud features was also compared. RESULTS: The 16-, 32-, 64-, and 1024-dimensional hemodynamic cloud features were extracted with the PointNet-based model, respectively, and the four types of cloud features in combination with the geometrical parameters and hemodynamic parameters were respectively applied to classify the rupture status of IAs. The best classification outcomes were achieved in the case of 16-dimensional hemodynamic cloud features, the accuracy of XGBoost, CatBoost, SVM, LightGBM, and LR algorithms was 0.887, 0.857, 0.854, 0.857, and 0.908, respectively, and the AUCs were 0.917, 0.934, 0.946, 0.920, and 0.944. In contrast, when only utilizing geometrical parameters and hemodynamic parameters, the accuracies were 0.836, 0.816, 0.826, 0.832, and 0.885, respectively, with AUC values of 0.908, 0.922, 0.930, 0.884, and 0.921. CONCLUSION: In this paper, classification models for IAs rupture status were constructed by integrating a PointNet-based model and machine learning algorithms. Experiments demonstrated that hemodynamic cloud features had a certain contribution weight to the classification of IAs rupture status. When 16-dimensional hemodynamic cloud features were added to the morphological and hemodynamic features, the models achieved the highest classification accuracies and AUCs. Our models and algorithms would provide valuable insights for the clinical diagnosis and treatment of IAs.

Investigation on drag reduction on rotating blade surfaces with microtextures.

To enhance the aerodynamic performance of aero engine blades, simulations and experiments regarding microtextures to reduce the flow loss on the blade surfaces were carried out. First, based on the axisymmetric characteristics of the impeller, a new simulation method was proposed to determine the aerodynamic parameters of the blade model through the comparison of flow field characteristics and simulation results. Second, the placement position and geometrical parameters (height, width, and spacing) of microtextures with lower energy loss were determined by our simulation of microtextures on the blade surface, and the drag reduction mechanism was analyzed. Triangular ribs with a height of 0.2 mm, a width of 0.3 mm, and a spacing of 0.2 mm exhibited the best drag reduction, reducing the energy loss coefficient and drag by 1.45% and 1.31% for a single blade, respectively. Finally, the blades with the optimal microtexture parameters were tested in the wind tunnel. The experimental results showed that the microtexture decreased energy loss by 3.7% for a single blade under 57° angle of attack and 136.24 m/s, which was favorable regarding the drag reduction performance of the impeller with 45 blades.

Exploring the acoustic potential of 3D printed micro-perforated panels: A comparative analysis.

In the present study, the sound absorption performance of inhomogeneous Micro-Perforated Panels (MPPs) with multiple cavities is investigated. Two models, a three-cavity system and a four-cavity system, are proposed and a numerical study is performed using MATLAB. The models are validated through experimental analysis in an impedance tube. The study meticulously varies the geometrical parameters, including pore diameter, thickness of the MPP, perforation ratio, and back-cavity length. It is found that MPPs with a greater number of sub-cavities have a better sound absorption coefficient than two-cavity systems. The results suggest that the back air cavity is predominantly responsible for multiple peaks, ensuring wideband sound absorption. It is also found that smaller perforation ratios for sub-cavities with larger pore diameters improve sound absorption performance in the lower frequency region. The study indicates that a pore diameter of less than 0.5 mm should be used for better sound absorption above the range of 800-850 Hz, and back cavity length has greater control than pore diameter between 850 Hz and 2000 Hz to make the curve smooth with less fluctuation. The findings have significant implications for the design of MPPs for real-world applications.

The effect of geometrical parameters of skin brachytherapy patch source on depth dose distribution using Monte Carlo simulation.

Brachytherapy of superficial skin tumors using beta-emitting sources is a method that has been investigated by some researchers in both simulation and experimental studies with promising results. In the current study, the effect of geometrical parameters of some relevant radionuclides including Y-90, Re-188, P-32, and Ho-166 on the depth dose distribution in skin tissue has been investigated through Monte Carlo simulation. MCNPX Monte Carlo code was employed to model the above-mentioned patch sources in cylindrical format and then the effect of patch geometrical parameters including the source-to-skin distance (SSD), patch thickness, and patch diameter on depth dose distribution was assessed through modeling and calculation of the dose inside a cubic phantom mimicking the skin tissue. The obtained results demonstrated that increasing the SSD, patch thickness, and patch diameter (with the same activity) will reduce the depth dose distribution. Changing the SSD has a more significant effect on the dose gradient within the depth than other geometrical parameters. It was also observed that the effect of patch diameter on the skin-delivered dose gets less sensible as the patch size goes beyond the range of beta radiation inside tissue. Finally, it can be concluded that the patch source geometrical parameters can affect the depth dose distribution inside the skin tissue. This fact may be of concern regarding the delivery of a high radiation dose in a single treatment session. Therefore, variations of patch source geometrical parameters should be considered during the skin dose calculation plan.

Soft pneumatic muscles for post-stroke lower limb ankle rehabilitation: leveraging the potential of soft robotics to optimize functional outcomes.

Introduction: A soft pneumatic muscle was developed to replicate intricate ankle motions essential for rehabilitation, with a specific focus on rotational movement along the x-axis, crucial for walking. The design incorporated precise geometrical parameters and air pressure regulation to enable controlled expansion and motion. Methods: The muscle's response was evaluated under pressure conditions ranging from 100-145 kPa. To optimize the muscle design, finite element simulation was employed to analyze its performance in terms of motion range, force generation, and energy efficiency. An experimental platform was created to assess the muscle's deformation, utilizing advanced techniques such as high-resolution imaging and deep-learning position estimation models for accurate measurements. The fabrication process involved silicone-based materials and 3D-printed molds, enabling precise control and customization of muscle expansion and contraction. Results: The experimental results demonstrated that, under a pressure of 145 kPa, the y-axis deformation (y-def) reached 165 mm, while the x-axis and z-axis deformations were significantly smaller at 0.056 mm and 0.0376 mm, respectively, highlighting the predominant elongation in the y-axis resulting from pressure actuation. The soft muscle model featured a single chamber constructed from silicone rubber, and the visually illustrated and detailed geometrical parameters played a critical role in its functionality, allowing systematic manipulation to meet specific application requirements. Discussion: The simulation and experimental results provided compelling evidence of the soft muscle design's adaptability, controllability, and effectiveness, thus establishing a solid foundation for further advancements in ankle rehabilitation and soft robotics. Incorporating this soft muscle into rehabilitation protocols holds significant promise for enhancing ankle mobility and overall ambulatory function, offering new opportunities to tailor rehabilitation interventions and improve motor function restoration.

Robust Rules for Optimal Colorimetric Sensing Based on Gold Nanoparticle Aggregation.

Spurred by outstanding optical properties, chemical stability, and facile bioconjugation, plasmonic metals have become the first-choice materials for optical signal transducers in biosensing. While the design rules for surface-based plasmonic sensors are well-established and commercialized, there is limited knowledge of the design of sensors based on nanoparticle aggregation. The reason is the lack of control over the interparticle distances, number of nanoparticles per cluster, or multiple mutual orientations during aggregation events, blurring the threshold between positive and negative readout. Here we identify the geometrical parameters (size, shape, and interparticle distance) that allow for maximizing the color difference upon nanoparticle clustering. Finding the optimal structural parameters will provide a fast and reliable means of readout, including unaided eye inspection or computer vision.

Geometrical Changes of the Aorta as Predictors for Thromboembolic Events After EVAR With the Anaconda Stent-Graft.

PURPOSE: Thromboembolic events (TE), including limb graft occlusion (LGO) and distal limb embolization (DLE), are common complications after endovascular aneurysm repair (EVAR). The aim of this study was to find predictors for TE in patients treated with the Anaconda stent-graft for infrarenal aneurysms. MATERIALS AND METHODS: Geometrical and anatomical variables were retrospectively analyzed in a consecutive Anaconda cohort. Pre- and postoperative CT scans were used to derive geometrical parameters length, curvature, torsion, and tortuosity index (TI) from the center lumen lines (CLLs). Limb characteristics, pre-to-post EVAR and mid-term-follow-up changes in the parameters were evaluated for their predictive value for TE. RESULTS: Eighty-four patients (mean age 74±8.3 years, 74 men) were enrolled. The risk of TE was lowered with pre-to-post implant decreasing TI (steps of 0.05: OR: 1.30, 95% CI: 1.01-1.66, p=0.04), pre-to-post implant decreasing mean curvature (OR: 1.08, 95% CI: 1.01-1.16, p=0.03), and a larger degree of circumferential common iliac artery (CIA) calcification (OR: 0.98, 95% CI: 0.97-1.00, p=0.03). The only LGO predictor was the caudal relocation of maximal curvature after EVAR (OR: 1.01, 95% CI: 1.00-1.01, p=0.04). Preventors of DLE were CIA diameter (OR: 0.87, 95% CI: 0.76-0.99, p=0.04), circumferential CIA calcification (OR: 0.97, 95% CI: 0.95-1.00, p=0.03), mean and maximal curvature of the preoperative aortoiliac trajectory (OR: 0.86, 95% CI: 0.79-0.94, p<0.01 and OR: 0.97, 95% CI: 0.95-1.00, p=0.03, respectively) and pre-to-postoperative decrease in mean curvature (OR: 1.11, 95% CI: 1.02-1.21, p=0.02). Midterm TE predictors were length (OR: 0.95, 95% CI: 0.89-1.01, p=0.08) and torsion maximum location (OR: 1.01, 95% CI: 0.99-1.01, p=0.10). CONCLUSION: The present study confirms that treatment of infrarenal AAA with an Anaconda stent-graft is related to a relatively high TE rate which decreases with a pre-to-postoperative reduction in curvature and TI, and a larger degree of circumferential CIA calcification. In other words, more aortoiliac straightening and more circumferential CIA calcification may prevent TE development after EVAR with this stent-graft.

A critical review on solar chimney power plant technology: influence of environment and geometrical parameters, barriers for commercialization, opportunities, and carbon emission mitigation.

Solar chimney power plant (SCPP) is one of the promising technologies to convert solar energy into carbon-free power generation. It has cost competitiveness, environment friendly and longer service life. Although remarkable advancements were achieved, commercialization aspect of the SCPP has not been established so far. Feasibility assessment of the large-scale plants was carried out by researchers in different climatic conditions across the globe but none of the studies materialized to date. However, it is almost four decades from the development of the first prototype, and no studies have been discussed the barriers to commercialization of the SCPP yet. Therefore, in this present study, a-state-of-the-art review has been presented which discussed the overview of SCPP technologies, factors affecting the flow and performance characteristics of the plant and major barriers in the commercialization aspect of the plant. The overview of SCPP technology including its global status and recent advances are spotlighted. The power potential and carbon emission mitigation of the SCPP based on the climatic condition and geographical location was studied by taking India as an example. In addition to that, the major challenges and opportunities in the SCPP are also addressed. Based on the analysis, a few recommendations are given for commercialization the plant.

Effect of Combustion Chamber Geometrical Parameters on the Decomposition and Combustion Characteristics of an ADN-Based Thruster.

In this paper, numerical simulations were used to study the decomposition and combustion processes inside the 0.2 N-class ADN-based thruster, and the effects of two geometrical parameters (length and diameter) of the combustion chamber on the combustion performance were evaluated. The decomposition and combustion processes of the thruster were simulated using a reduced chemical reaction mechanism with 22 components and 20 reactions steps. According to the distribution of the basic physical fields, the variation patterns of the pressure field, velocity field, temperature field, and key component parameters caused by different combustion chamber geometrical parameters were observed and analyzed. The results show that the specific impulse and thrust of the thruster increased and then decreased with the increase of the combustion chamber diameter. When the combustion chamber diameter is 7.9 mm, the specific impulse reaches the maximum value of 206.6 s. Additionally, the specific impulse increased from 186 s to 206 s when the combustion chamber length was changed from 7 mm to 11 mm; the specific impulse increased gradually but not significantly, and the growth trend started to flatten out. The results from the paper can serve as a reference for the design and vacuum testing of an ADN-based thruster.

Progress and challenges of helical-shaped geothermal heat exchangers.

Among various types of renewable energy, geothermal energy is recognized as an effective method for supplying thermal energy. Ground heat exchangers, as the main part of a geothermal energy system, are utilized for the extraction of the heat from the ground. Helical-shaped geothermal heat exchangers are very popular in this field as they need less land space compared to the other traditional straight ones. They have simple assembly and a high density of coils in their configuration. Considerable efforts have been done on the development of this type of geothermal heat exchanger. However, this topic has not been subject to a review. To address this issue, we present an overview of the potentials and challenges of helical-shaped geothermal heat exchangers in this study. The environmental and economic aspects, recent progress about the numerical simulations, soil features, different types and arrangements, and geometrical parameters for this type of heat exchangers are investigated. The installation cost is a critical challenge in the practical applications of these exchangers. However, the previous studies are mostly focused on the technical evaluation and optimization of the thermal performance of this type of heat exchanger, while little attention is paid to their installation costs. It is essential to understand the potential environmental impacts of each renewable energy technology to have a correct evaluation of the system. The life cycle assessment can be used as a proper method to assess the environmental issues of the helical-shaped geothermal heat exchanger in the studies.

Multiscale structural characterization of the vertebral endplate in animal models.

Research in the field of spinal biomechanics, including analyses of the impact of implants on the stability of the spine, is conducted extensively in animal models. One of the basic problems in spinal implantation is the transfer and distribution of loads carried by the spine on the surfaces of the vertebral bodies. An important factor in proper cooperation of spinal implants with the vertebrae is the endplate (EP), which is why the EP in the animal model used for testing should be as similar as possible to the human EP. Therefore, this study involved multiscale structural and morphometric analyses of the animal models most commonly used in spinal biomechanics research, i.e. pig, ovine, and bovine tail. The tests were performed on 28 lumbar porcine, ovine, and bovine vertebrae. Both cranial and caudal EPs were analysed in three selected areas: anterior, middle, and posterior EPs. The conducted tests included a morphometric analysis of the trabecular bone (TB) layer of the EP as well as microscopic analysis at the mesoscale (total thickness) and microscale (thickness of the individual EP layers). The porcine EP had a characteristic increased circumferential thickness (~3 mm) with a significant narrowing in the central region (50%-60%). The convex cranial ovine EP had a constant thickness throughout the cross-section and the concave caudal EP showed ~35% narrowing in the central region. The thickest EPs were observed in the bovine tail model with negligibly small narrowing in the central region (~5%). The thickness of the cartilaginous layer in the porcine and bovine models reached up to 1 mm in the peripheral regions and decreased in the central part. The growth plate layer had a similar thickness in all the models. On the other hand, the narrowing of the total thickness of the EPs in the central region was mainly due to a decrease in the VEP thickness. In the ovine and bovine models, the central region of the EP was characterized by large isotropy and trabeculae of mixed or rod-like shape. By contrast, in the pig, this region had plate-like trabeculae of anisotropic nature. The porcine model was identified as best reflecting the shape and structure of the human EP and as the best surrogate model for the human EP model. This choice is particularly important in the context of biomechanical research.

Investigation of Forced Convection Enhancement and Entropy Generation of Nanofluid Flow through a Corrugated Minichannel Filled with a Porous Media.

Corrugating channel wall is considered to be an efficient procedure for achieving improved heat transfer. Further enhancement can be obtained through the utilization of nanofluids and porous media with high thermal conductivity. This paper presents the effect of geometrical parameters for the determination of an appropriate configuration. Furthermore, the optimization of forced convective heat transfer and fluid/nanofluid flow through a sinusoidal wavy-channel inside a porous medium is performed through the optimization of entropy generation. The fluid flow in porous media is considered to be laminar and Darcy-Brinkman-Forchheimer model has been utilized. The obtained results were compared with the corresponding numerical data in order to ensure the accuracy and reliability of the numerical procedure. As a result, increasing the Darcy number leads to the increased portion of thermal entropy generation as well as the decreased portion of frictional entropy generation in all configurations. Moreover, configuration with wavelength of 10 mm, amplitude of 0.5 mm and phase shift of 60° was selected as an optimum geometry for further investigations on the addition of nanoparticles. Additionally, increasing trend of average Nusselt number and friction factor, besides the decreasing trend of performance evaluation criteria (PEC) index, were inferred by increasing the volume fraction of the nanofluid (Al2O3 and CuO).

The Influence of Printing Orientation on Surface Texture Parameters in Powder Bed Fusion Technology with 316L Steel.

Laser technologies for fast prototyping using metal powder-based materials allow for faster production of prototype constructions actually used in the tooling industry. This paper presents the results of measurements on the surface texture of flat samples and the surface texture of a prototype of a reduced-mass lathe chuck, made with the additive technology-powder bed fusion. The paper presents an analysis of the impact of samples' orientation on the building platform on the surface geometrical texture parameters (two-dimensional roughness profile parameters (Ra, Rz, Rv, and so on) and spatial parameters (Sa, Sz, and so on). The research results showed that the printing orientation has a very large impact on the quality of the surface texture and that it is possible to set digital models on the building platform (parallel-0° to the building platform plane), allowing for manufacturing models with low roughness parameters. This investigation is especially important for the design and 3D printing of microelectromechanical systems (MEMS) models, where surface texture quality and printable resolution are still a large problem.

The Synthesis of New Thermal Stable Schiff Base/Ester Liquid Crystals: A Computational, Mesomorphic, and Optical Study.

A Schiff base supramolecular 4-[(4-(hexyloxy)phenylimino)methyl]benzoic acid and a new series of Schiff base/ester linkages named 4-substitutedphenyl 4-[(4-(hexyloxy)phenylimino)methyl]benzoate liquid crystals were synthesized. The thermal stability, mesomorphic, and optical behavior of the prepared compounds were characterized by differential scanning calorimetry (DSC), Thermogravemetric analysis (TGA), polarized optical microscopy (POM), and UV spectroscopy. FT-IR, 1H-NMR, 13C-NMR, and elemental analyses were carried out to elucidate and confirm the molecular structures of the synthesized compounds. The investigated series comprising different sized terminal polar groups changed between CH(CH3)2, H, I, and F. It was found that the supramolecular imino acid dimer is enantiotropic dimorphic, with a wide SmA phase and a good N phase range. The other series of terminally substituted Schiff base/esters are mesomorphic with a high thermal stable SmA phase, except the iodo derivative, which showed dimorphic SmA and N phases. The effect of the position and the orientation of the cores, as well as the terminal substituent of the type and the stability of the mesophase, were studied. A computational theoretical study of the effects of the van der Waal's volume, the Hammett substituent coefficient, the inductive sigma constant, and other geometrical parameters were discussed. The study revealed that the planarity of the two phenyl rings attached with an imino linking group impacted the resonance effect of the terminal substituents rather than their inductive effect. A detailed study on the effect of the estimated thermal parameters, as well as their geometrical planarity with the type and stability of the formed mesophase, was discussed.

Nanohole array plasmonic biosensors: Emerging point-of-care applications.

Point-of-care (POC) applications have expanded hugely in recent years and is likely to continue, with an aim to deliver cheap, portable, and reliable devices to meet the demands of healthcare industry. POC devices are designed, prototyped, and assembled using numerous strategies but the key essential features that biosensing devices require are: (1) sensitivity, (2) selectivity, (3) specificity, (4) repeatability, and (5) good limit of detection. Overall the fabrication and commercialization of the nanohole array (NHA) setup to the outside world still remains a challenge. Here, we review the various methods of NHA fabrication, the design criteria, the geometrical features, the effects of surface plasmon resonance (SPR) on sensing as well as current state-of-the-art of existing NHA sensors. This review also provides easy-to-understand examples of NHA-based POC biosensing applications, its current status, challenges, and future prospects.

Experimental Study of Macro and Microgeometric Defects in Drilled Carbon Fiber Reinforced Plastics by Laser Beam Machining.

Plastic matrix composite materials are an excellent choice for structural applications where high strength-weight and stiffness-weight ratios are required. These materials are being increasingly used in diverse industrial sectors, particularly in aerospace. Due to the strict tolerances required, they are usually machined with drilling cycles due to the type of mounting through rivets. In this sense, laser beam drilling is presented as an alternative to conventional drilling due to the absence of tool wear, cutting forces, or vibrations during the cutting process. However, the process carries with it other problems that compromise the integrity of the material. One of these is caused by the high temperatures generated during the interaction between the laser and the material. In this work, variance analysis is used to study the influence of scanning speed and frequency on macro geometric parameters, surface quality, and defects (taper and heat affected zone). Also, in order to identify problems in the wall of the drill, stereoscopic optical microscopy (SOM) and scanning electron microscopy (SEM) techniques are used. This experimental procedure reveals the conditions that minimize deviations, defects, and damage in machining holes.

Enhancement of Colour Effects of Dyed-Yarn Mixed Fabrics Using Cramming Motion and Finer Polyester Yarns.

This paper reports the study of the effects of cramming motion implemented during weaving and finer weft yarns used on dyed-yarn mixed woven fabrics produced by using raw white warps and multicolored-wefts. The cramming motion was used to increase the dyed-weft yarns cover factor of fabric, and thus, to reduce the negative effect of white warp floats at the fabric face on the color attributes of fabric. The surface structure of fabric was characterized by using several key geometrical parameters that determined the resultant fabric color attributes. The effects of fabric structure and density, weft yarn count, and the introduction of black yarn on the fabric face layer on the fabric surface geometrical parameters, physical properties, as well as color attributes were investigated under the implementation of cramming motion on the fabric. The color attributes of fabrics using cramming motion and finer yarns were also compared to the fabrics without cramming motion. The experimental results indicate that the weft yarn density and cover factor of fabric face layer are increased by applying cramming motion and finer yarns for fabricating the blue-red and/or black mixed fabrics. Consequently, the fabric lightness can be further reduced for achieving a better color effect on colorful and figured woven fabrics mainly using dyed-wefts for color mixing.

A numerical study on the effect of geometrical parameters and loading profile on the expansion of stent.

BACKGROUND: Stenting has been proposed as an effective treatment to restore blood flow in obstructed arteries by plaques. Although several modified designs for stents have been suggested, most designs have the risk of disturbing blood flow. OBJECTIVE: The main objective is to propose a stent design to attain a uniform lumen section after stent deployment. METHODS: Mechanical response of five different designs of J & J Palmaz-Schatz stent with the presence of plaque and artery are investigated; four stents have variable strut thickness of different magnitudes and the rest one is a uniform-strut-thickness stent. Nonlinear finite element is employed to simulate the expansion procedure of the intended designs using ABAQUS explicit. RESULTS: The stent design whose first cell thickness linearly increases by 35 percent, exhibits the best performance, that is it has the lowest recoiling and stress induced in the intima for a given lumen gain. It also enjoys the minimal discrepancy between the final at the distal and proximal ends. CONCLUSIONS: A uniform widened artery can be achieved by using the stent design with 35 percent increase in its first cell, which provides the possibility to prevent from disturbing blood flow and consequently post-operation complications.

Experimental Investigation on the Joining of Aluminum Alloy Sheets Using Improved Clinching Process.

Aluminum alloy sheets have been widely used to build the thin-walled structures by mechanical clinching technology in recent years. However, there is an exterior protrusion located on the lower sheet and a pit on the upper sheet, which may restrict the application of the clinching technology in visible areas. In the present study, an improved clinched joint used to join aluminum alloy sheets was investigated by experimental method. The improved clinching process used for joining aluminum alloy evolves through four phases: (a) localized deformation; (b) drawing; (c) backward extrusion; and (d) mechanical interlock forming. A flat surface can be produced using the improved clinching process. Shearing strength, tensile strength, material flow, main geometrical parameters, and failure mode of the improved clinched joint were investigated. The sheet material was compressed to flow radially and upward using a punch, which generated a mechanical interlock by producing severe localized plastic deformation. The neck thickness and interlock of the improved clinched joint were increased by increasing the forming force, which also contributed to increase the strength of the clinched joint. The improved clinched joint can get high shearing strength and tensile strength. Three main failure modes were observed in the failure process, which were neck fracture mode, button separation mode, and mixed failure mode. The improved clinched joint has better joining quality to join aluminum alloy sheets on the thin-walled structures.

Design and Optimization of a Stationary Electrode in a Vertically-Driven MEMS Inertial Switch for Extending Contact Duration.

A novel micro-electro-mechanical systems (MEMS) inertial microswitch with a flexible contact-enhanced structure to extend the contact duration has been proposed in the present work. In order to investigate the stiffness k of the stationary electrodes, the stationary electrodes with different shapes, thickness h, width b, and length l were designed, analyzed, and simulated using ANSYS software. Both the analytical and the simulated results indicate that the stiffness k increases with thickness h and width b, while decreasing with an increase of length l, and it is related to the shape. The inertial micro-switches with different kinds of stationary electrodes were simulated using ANSYS software and fabricated using surface micromachining technology. The dynamic simulation indicates that the contact time will decrease with the increase of thickness h and width b, but increase with the length l, and it is related to the shape. As a result, the contact time decreases with the stiffness k of the stationary electrode. Furthermore, the simulated results reveal that the stiffness k changes more rapidly with h and l compared to b. However, overlarge dimension of the whole microswitch is contradicted with small footprint area expectation in the structure design. Therefore, it is unreasonable to extend the contact duration by increasing the length l excessively. Thus, the best and most convenient way to prolong the contact time is to reduce the thickness h of the stationary electrode while keeping the plane geometric structure of the inertial micro-switch unchanged. Finally, the fabricated micro-switches with different shapes of stationary electrodes have been evaluated by a standard dropping hammer system. The test maximum contact time under 288 g acceleration can reach 125 µs. It is shown that the test results are in accordance with the simulated results. The conclusions obtained in this work can provide guidance for the future design and fabrication of inertial microswitches.