The emergence of COVID-19 in South Korea, and the public and private sector response to it, serves as a valuable case study for countries facing similar outbreaks. This article focuses on how Korean ...health officials implemented drive-through and walk-through diagnostic testing, and extensive movement and contact tracing, to identify and inform exposed members of the public. Mobile applications from both government agencies and private developers played an important role in guiding people to testing centers, communicating movement trajectories of confirmed cases on digital maps, and tracking the health and movements of travelers and others at risk of exposure. This case study illustrates the importance of rapid adaptation of transportation infrastructure and location-based information technology to respond to public health crises, and how governments can learn from experimentation and past experience to accelerate these responses.
Research on wearable electronic devices that can be directly integrated into daily textiles or clothes has been explosively grown holding great potential for various practical wearable applications. ...These wearable electronic devices strongly demand 1D electronic devices that are light–weight, weavable, highly flexible, stretchable, and adaptable to comport to frequent deformations during usage in daily life. To this end, the development of 1D electrodes with high stretchability and electrical performance is fundamentally essential. Herein, the recent process of 1D stretchable electrodes for wearable and textile electronics is described, focusing on representative conductive materials, fabrication techniques for 1D stretchable electrodes with high performance, and designs and applications of various 1D stretchable electronic devices. To conclude, discussions are presented regarding limitations and perspectives of current materials and devices in terms of performance and scientific understanding that should be considered for further advances.
1D stretchable electrodes and electronic devices are of great importance for developing advanced wearable electronics in the form of daily clothes. The state‐of‐the‐art advances in stretchable conductive fibers are systematically introduced in terms of their conductive materials, fabrication techniques, electronic devices, and applications. An outlook and challenges for future research are also provided.
•Fabrication of facile, scalable bio-mimicking hierarchical micro-nanostructure.•Capacitive pressure sensors show a high sensitivity and fast response time.•Capability for pulse monitoring at the ...human wrist with the bilayer pressure sensor.•Promising for the soft electronics and potential in electronic skin applications.
Capacitive pressure sensors are an important part of flexible/stretchable electronic skin applications. The fabrication of most of the reported polydimethylsiloxane (PDMS) based capacitive pressure sensors involves complex techniques and expensive tools. To improve the capacitive sensing properties of PDMS, a bio-mimicking hierarchical micro- and nanostructure that are facile, cost-effective, and scalable is presented in this work. Red rose petals are known to consist of hierarchical micropapillae and nanofolds. So, the artificial fabrication of these micro- and nanostructures provides a necessary roughness for pressure sensors. The sensors comprise both single and double layers of well-defined PDMS structures with indium tin oxide (ITO) electrodes. This capacitive pressure sensor allows the sensitive detection of both static and dynamic external stimuli. By successfully mimicking rose petals whose hemisphere contains micropapillae and nanofolds, ultra-sensitive capacitive pressure sensors show a sensitivity of 0.055 kPa−1 over a wide pressure range (0.5–10 kPa) with a fast response time (<200 ms) and high stability. The sensing performance also checked for capability to accurately pulse monitoring at the human wrist which demonstrated the bilayer pressure sensor has promising application in wearable electronics.
A flexible and sensitive textile‐based pressure sensor is developed using highly conductive fibers coated with dielectric rubber materials. The pressure sensor exhibits superior sensitivity, very ...fast response time, and high stability, compared with previous textile‐based pressure sensors. By using a weaving method, the pressure sensor can be applied to make smart gloves and clothes that can control machines wirelessly as human–machine interfaces.
Stretchable conductive fibers have received significant attention due to their possibility of being utilized in wearable and foldable electronics. Here, highly stretchable conductive fiber composed ...of silver nanowires (AgNWs) and silver nanoparticles (AgNPs) embedded in a styrene–butadiene–styrene (SBS) elastomeric matrix is fabricated. An AgNW‐embedded SBS fiber is fabricated by a simple wet spinning method. Then, the AgNPs are formed on both the surface and inner region of the AgNW‐embedded fiber via repeated cycles of silver precursor absorption and reduction processes. The AgNW‐embedded conductive fiber exhibits superior initial electrical conductivity (σ0 = 2450 S cm−1) and elongation at break (900% strain) due to the high weight percentage of the conductive fillers and the use of a highly stretchable SBS elastomer matrix. During the stretching, the embedded AgNWs act as conducting bridges between AgNPs, resulting in the preservation of electrical conductivity under high strain (the rate of conductivity degradation, σ/σ0 = 4.4% at 100% strain). The AgNW‐embedded conductive fibers show the strain‐sensing behavior with a broad range of applied tensile strain. The AgNW reinforced highly stretchable conductive fibers can be embedded into a smart glove for detecting sign language by integrating five composite fibers in the glove, which can successfully perceive human motions.
Ag nanowire reinforced highly stretchable conductive fiber is developed using simple wet spinning method, which consists of silver nanowires and nanoparticles embedded in elastomeric polymer matrix. The composite fiber can preserve its electrical property under large strain and has superior strain‐sensing behavior. It can be utilized in the wearable smart glove for detecting human motions such as sign language.
Since the first journal article on structural engineering applications of neural networks (NN) was published, there have been a large number of articles about structural analysis and design problems ...using machine learning techniques. However, due to a fundamental limitation of traditional methods, attempts to apply artificial NN concept to structural analysis problems have been reduced significantly over the last decade. Recent advances in deep learning techniques can provide a more suitable solution to those problems. In this study, versatile background information, such as alleviating overfitting methods with hyper-parameters, is presented. A well-known ten bar truss example is presented to show condition for neural networks, and role of hyper-parameters in the structures.
We propose a novel graphics processing unit (GPU) algorithm that can handle a large‐scale 3D fast Fourier transform (i.e., 3D‐FFT) problem whose data size is larger than the GPU's memory. A 1D ...FFT‐based 3D‐FFT computational approach is used to solve the limited device memory issue. Moreover, to reduce the communication overhead between the CPU and GPU, we propose a 3D data‐transposition method that converts the target 1D vector into a contiguous memory layout and improves data transfer efficiency. The transposed data are communicated between the host and device memories efficiently through the pinned buffer and multiple streams. We apply our method to various large‐scale benchmarks and compare its performance with the state‐of‐the‐art multicore CPU FFT library (i.e., fastest Fourier transform in the West FFTW) and a prior GPU‐based 3D‐FFT algorithm. Our method achieves a higher performance (up to 2.89 times) than FFTW; it yields more performance gaps as the data size increases. The performance of the prior GPU algorithm decreases considerably in massive‐scale problems, whereas our method's performance is stable.
Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory is presented. The core of sandwich beam is fully metal or ceramic and ...skins are composed of a functionally graded material across the depth. Governing equations of motion and boundary conditions are derived from the Hamilton’s principle. Effects of power-law index, span-to-height ratio, core thickness and boundary conditions on the natural frequencies, critical buckling loads and load–frequency curves of sandwich beams are discussed. Numerical results show that the above-mentioned effects play very important role on the vibration and buckling analysis of functionally graded sandwich beams.
A flexible pressure sensor with high performances is one of the promising candidates for achieving electronic skins (E‐skin) related to various applications such as wearable devices, health ...monitoring systems, and artificial robot arms. The sensitive response for external mechanical stimulation is fundamentally required to develop the E‐skin which imitates the function of human skin. The performance of capacitive pressure sensors can be improved using morphologies and structures occurring in nature. In this work, highly sensitive capacitive pressure sensors based on a porous structure of polydimethylsiloxane (PDMS) thin film, inspired on the natural multilayered porous structures seen in mushrooms, diatoms, and spongia offilinalis, have been developed and evaluated. A bioinspired porous dielectric layer is used, resulting in high‐performance pressure sensors with high sensitivity (0.63 kPa−1), high stability over 10 000 cycles, fast response and relaxation times, and extremely low‐pressure detection of 2.42 Pa. Additionally, the resulting pressure sensors are demonstrated to fabricate multipixel arrays, thus achieving successful real‐time tactile sensing of various touch shapes. The developed high‐performance flexible pressure sensors may open new opportunities for innovative applications in advanced human‐machine interface systems, robotic sensory systems, and various wearable health monitoring devices.
A highly sensitive bioinspired porous structured pressure sensor is demonstrated that can detect extremely light weight objects such as an ant. The porous structured pressure sensor is pixelated into a 15 × 15 array and based on the fast response time of the pressure sensor, real‐time tactile mapping is demonstrated under various pressures.
Numerous studies have developed novel form-finding methods of tensegrity structures using various techniques. Previous works have been limited by the lack of a fully automatic grouping technique in ...the form-finding process. In this study, an advanced form-finding method of tensegrity structures using a fully automatic labeling that can specify the member types. Constraint optimization problems were then used in the form-finding processes to minimize fitness functions by using a double-loop genetic algorithm. A well-known truncated tetrahedral tensegrity is presented to demonstrate the accuracy and efficiency of the proposed method. In conclusion, a very good performance of presented method has been shown in the results.
•An advanced method for form-finding of tensegrity structures is presented.•A fully automatic group selection can be obtained using a penalty strategy with discrete strut condition.•A double-loop GA is used to effectively guide the searching direction towards promising solutions.•The constraint minimization problems by using the equilibrium equations are used.•A very good performance of presented method has been shown in the results.
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