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Visualizations of the microwave electric and magnetic near-field distributions of radio-frequency (RF) filters were performed using the technique of thermoelastic optical indicator microscopy (TEOIM). New optical indicators based on periodic dielectric-metal structures were designed for electric field visualization. Depending on the structure orientation, such metasurface-based indicators allow separately visualization of the E x and E y components of the in-plane electric field. Numerical simulations were conducted to examine the working principle of the designed indicator structures, and the results were compared to the experimental, showing good agreement. In addition, the 3D visualization of the microwave near-field distribution was built, to show the field intensity and distribution dependencies on the distance from the RF filter.

Ecoflex is widely used in bioelectronics due to its outstanding properties of low modulus and large stretchability. For its use as an encapsulation layer in multi-channel wearable devices, a patterning procedure is essential. However, conventional patterning strategies for Ecoflex, such as soft lithography, punching, and laser ablation, lack sufficient quality and process compatibility. To address this, we propose a process-compatible method of patterning Ecoflex by developing Photo-patternable Ecoflex (PPE). The PPE layer, used as an encapsulation layer, effectively dissipates strain energy at homogeneous interfaces, resulting in a 50% increase in electrical conductance under 250% strain. Using PPE, we fabricated intrinsically stretchable multi-sensors that monitor bio-signals like glucose, lactate, pH, and humidity in sweat. These sensors maintain durable sensitivity under strain up to 50% and for 1000 cycles at 20% strain. Finally, we mounted these stretchable multi-chemical sensors on an arm to monitor glucose and lactate levels in sweat.

Although the Korean government plans to increase its share of variable renewable energies (VREs), the Korean power market is not sufficiently mature to accommodate a large increase in VRE generation. Thus, the Korean system operator plans to introduce a two-settlement, and an imbalance settlement is also under consideration, among several options. Therefore, this study analyzes how many incentives are given for prediction accuracy under several imbalance settlement schemes adopted from European and US power markets. Results show that the imbalance settlement consisting of threshold and penalty terms is useful for rule-makers, who can control revenue differences between the groups with different prediction accuracies by adjusting the two terms. The suggestion given in the paper will be useful for not only the Korean power market but also for the countries that plan to establish the imbalance settlement rules while increasing renewable energy.

We measured the glucose concentration by using the real-time electromagnetic interaction between probe-tip and glucose solution using a microwave biosensor. The microwave biosensor, consisting of a dielectric resonator coupled to the probe-tip, allows observation of the small variation of the glucose concentration changes in the ranges of 0–300 mg/ml by measuring the microwave reflection coefficient S11. We could observe the concentration of glucose with a detectable resolution up to 1 mg/ml at an operating frequency of about f=4-5 GHz. The change of the glucose concentration is directly related to the change of the reflection coefficient due to the electromagnetic interaction between the microwave resonator and the glucose solution. The operational principal is explained by the plane-wave solution model. The measured signal-to-noise ratio was about 37 dB, and the minimum detectible signal was about 0.003 dB/(mg/ml). A glucose biosensor using a microwave resonator with probe provides a unique approach for glucose real-time monitoring.

We developed a microwave glucose sensor based on the modified first-order Hilbert curve design and measured glucose concentration in aqueous solutions by using a real-time microwave near-field electromagnetic interaction technique. We observed S21 transmission parameters of the sensor at resonant frequencies depend on the glucose concentration. We could determine the glucose concentration in the 0–250 mg/dL concentration range at an operating frequency of near 6 GHz. The measured minimum detectable signal was 0.0156 dB/(mg/dL) and the measured minimum detectable concentration was 1.92 mg/dL. The simulation result for the minimum detectable signal and the minimum detectable concentration was 0.0182 dB/(mg/dL) and 1.65 mg/dL, respectively. The temperature instability of the sensor for human glycemia in situ measurement range (27–34 °C for fingers and 36–40 °C for body temperature ranges) can be improved by the integration of the temperature sensor in the microwave stripline platform and the obtained data can be corrected during signal processing. The microwave signal–temperature dependence is almost linear with the same slope for a glucose concentration range of 50–150 mg/dL. The temperature correlation coefficient is 0.05 dB/°C and 0.15 dB/°C in 27–34 °C and 36–40 °C temperature range, respectively. The presented system has a cheap, easy fabrication process and has great potential for non-invasive glucose monitoring.

Recently, displays and optoelectronics have made remarkable development because they are the most frequently exposed applications to humanity. The pixel size has become smaller and a new form factor is needed for displays and optoelectronics beyond rigid ones. New material breakthroughs enabling new form factors with plastic-like flexibility, mechanical toughness as well as glass-like thermal/mechanical resistance and low thermal expansion are required. Sol–gel-derived siloxane hybrid material (Hybrimer), showing synergetic properties of organic and inorganic (O–I) materials, can be realized by chemical hybridization and dense O–I co-networks. In addition, the characteristics of hybrimer can be easily optimized via control of organic functional groups, sol–gel reaction, and polymerization steps. First, a sol–gel reaction and polymerization, which enables chemical hybridization of O–I groups, are introduced. Then, the various display and optoelectronic applications using hybrimer achieved by control of properties are provided: (i) patterning, (ii) passivation, (iii) glass-fabric reinforced film, and (iv) color conversion films. This paper includes a brief overview of fabrication process and applications using hybrimer developed over the past decades. Highlights Sol–gel-derived siloxane hybrid material (hybrimer) is composed of a chemical hybridization between organic and siloxane phase. Hybrimer can be simply fabricated using sol–gel reaction and polymerization. Properties of hybrimer can be easily tuned by controlling the organic groups and sol–gel reaction. Hybrimer can be applied to various display and optoelectronics.

Luminescent nanocrystals (NCs) have emerged as the high-performance wavelength converting materials in next-generation displays and energy conversion devices due to their unique optophysical properties, such as large Stokes or anti-Stokes shifts, narrow emission bandwidth, and tunable bandgap depending on size or composition. However, poor long-term stability in high temperature and humidity remains a critical issue for device applications. This instability is primarily due to irreversible changes in surface ligands or chemical structures/compositions when exposed to various severe environments. Various strategies have been reported to address these issues, such as the formation of inorganic shell layers and the fabrication of polymer-based nanocomposites. Although these strategies have improved stability, they exhibit degraded properties during long-term aging. Recently, sol–gel derived siloxane hybrid materials have been introduced to achieve stability for various NCs under actual operating conditions of displays and optoelectronic devices. This review will address recent progress in developing siloxane-encapsulated NCs with high stability in high temperature/humidity and under continuous light exposure. It will also introduce results on enhancing the environmental stability of various NCs, including lanthanide-doped transition metal-based NCs, semiconducting NCs, and metal halide perovskite NCs, as well as demonstrations of reliable devices. Graphical Abstract Highlights Research on luminescent nanocrystals (NCs) encapsulated by siloxane hybrids is discussed. The strategy for enhancing the stability of NCs is discussed. The results of stability improvement for NCs encapsulated by siloxane hybrids are investigated. Demonstrations of high-performance and stable NC-based optoelectronic devices are addressed.

For successful structural health monitoring and structural integrity evaluation of a laminated composite structure, it is important to study the effects of delamination on the propagations of the guided waves in a delaminated composite beam by using an accurate and computationally efficient method. Thus, we developed a “frequency-domain” spectral element model for the symmetric composite beams. First-order-shear-deformation-theory (FSDT) based Timoshenko beam theory and Mindlin-Herrmann rod theory are adopted for the flexural (bending) waves and axial (extensional) waves, respectively. A spectral element model is derived from the governing equations of motion by using the variation method in the frequency domain. After validating the accuracy of the proposed spectral element model, the model is used to investigate the effects of delamination on the propagation of guided waves in examples of composite beams.

Although racial-ethnic disparities in rates of births unintended by women have received substantial attention from demographers, little is known about the dyadic pregnancy intentions preceding the births of White, Black, and Hispanic women in the United States. We use birth records from the 2011–2013, 2013-2015, 2015–2017, and 2017–2019 waves of the National Survey of Family Growth to identify multiple types of agreement and disagreement in the pregnancy intentions of female and male co-conceivers around the time of conception, and assess racial-ethnic disparities in the prevalence of each of these scenarios. Our results showed that while 55% of births in the US were intended by both sex partners, 19% were unintended by both, and 26% were conceived in a context of dyadic disagreement over pregnancy intentions. Net of demographic and family trajectory characteristics, Black and Hispanic women’s births were more likely to be the product of disagreement, where the conception was unintended for women but intended for their male sex partners. In particular, Black women had the highest probability of experiencing births that were unwanted for them but intended for their male co-conceivers. Our findings highlight the importance of measuring and assessing dyadic pregnancy intentions to understand key racial-ethnic differences in the circumstances leading to conceptions, and their potential implications for child, parental, and family wellbeing.

For successful structural health monitoring and structural integrity evaluation of a laminated composite structure, it is important to study the effects of delamination on the propagations of the guided waves in a delaminated composite beam by using an accurate and computationally efficient method. Thus, we developed a “frequency-domain” spectral element model for the symmetric composite beams. First-order-shear-deformation-theory (FSDT) based Timoshenko beam theory and Mindlin-Herrmann rod theory are adopted for the flexural (bending) waves and axial (extensional) waves, respectively. A spectral element model is derived from the governing equations of motion by using the variation method in the frequency domain. After validating the accuracy of the proposed spectral element model, the model is used to investigate the effects of delamination on the propagation of guided waves in examples of composite beams.