Synergistic multi-doping effects on the Li7La3Zr2O12 solid electrolyte for fast lithium ion conduction.

Here, we investigate the doping effects on the lithium ion transport behavior in garnet Li7La3Zr2O12 (LLZO) from the combined experimental and theoretical approach. The concentration of Li ion vacancy generated by the inclusion of aliovalent dopants such as Al(3+) plays a key role in stabilizing the cubic LLZO. However, it is found that the site preference of Al in 24d position hinders the three dimensionally connected Li ion movement when heavily doped according to the structural refinement and the DFT calculations. In this report, we demonstrate that the multi-doping using additional Ta dopants into the Al-doped LLZO shifts the most energetically favorable sites of Al in the crystal structure from 24d to 96 h Li site, thereby providing more open space for Li ion transport. As a result of these synergistic effects, the multi-doped LLZO shows about three times higher ionic conductivity of 6.14 × 10(-4) S cm(-1) than that of the singly-doped LLZO with a much less efforts in stabilizing cubic phases in the synthetic condition

Prediction model of intention to use digital fitness services for health promotion during the COVID-19 pandemic: a gender-based multi-group analysis

As the number of people infected with COVID-19 in Korea is increasing, several measures have been implemented to gradually restrict outdoor activities and indoor gatherings while promoting a non-face-to-face social culture. In this study, we performed a gender-based multi-group analysis using a technology acceptance model (TAM) as an external variable for COVID-19 risk perception to verify the model’s predictive ability to increase participation behavior toward digital fitness services. We analyzed the data of 433 Koreans using an online survey consisting of 23 items. A structural equation model was used to verify the perceived ease of use (PEOU), perceived usefulness (PU), intention to use and exercise participation behavior of the TAM with COVID-19 risk perception as an external variable. First, our results showed that COVID-19 risk perception had a statistically higher significant and positive effect on PEOU (β = 0.170, t = 3.296, p < 0.001) than on PU (β = 0.130, t = 2.848, p = 0.004) of digital fitness services. Second, the PEOU of the digital fitness service was found to have a statistically higher significant positive effect on PU (β = 0.512, t = 9.728, p < 0.001) than on intention to use (β = 0.130, t = −2.774, p = 0.006). Third, the PU of digital fitness services was found to have a statistically significant positive effect on the intention to use (β = 0.684, t = 12.909, p < 0.001). Fourth, the intention to use the digital fitness service was found to have a statistically significant positive effect on exercise participation behavior (β = 0.796, t = 16.248, p < 0.001). Lastly, we observed a significant difference between men and women in COVID-19 risk perception and PEOU among the six paths established. Digital environments that encourage participation in exercises could promote health during a pandemic. This study highlighted the need to consider digital environments that encourage exercise participation in creating physical exercise contents as there was no significant difference in the intention to use digital fitness services between men and women

A Hybrid Approach Based on Variational Mode Decomposition for Analyzing and Predicting Urban Travel Speed

Predicting travel speeds on urban road networks is a challenging subject due to its uncertainty stemming from travel demand, geometric condition, traffic signals, and other exogenous factors. This uncertainty appears as nonlinearity, nonstationarity, and volatility in traffic data, and it also creates a spatiotemporal heterogeneity of link travel speed by interacting with neighbor links. In this study, we propose a hybrid model using variational mode decomposition (VMD) to investigate and mitigate the uncertainty of urban travel speeds. The VMD allows the travel speed data to be divided into orthogonal and oscillatory sub-signals, called modes. The regular components are extracted as the low-frequency modes, and the irregular components presenting uncertainty are transformed into a combination of modes, which is more predictable than the original uncertainty. For the prediction, the VMD decomposes the travel speed data into modes, and these modes are predicted and summed to represent the predicted travel speed. The evaluation results on urban road networks show that, the proposed hybrid model outperforms the benchmark models both in the congested and in the overall conditions. The improvement in performance increases significantly over specific link-days, which generally are hard to predict. To explain the significant variance of the prediction performance according to each link and each day, the correlation analysis between the properties of modes and the performance of the model are conducted. The results on correlation analysis show that the more variance of nondaily pattern is explained through the modes, the easier it was to predict the speed. Based on the results, discussions on the interpretation on the correlation analysis and future research are presented. Document type: Articl

Enhanced light harvesting in bulk heterojunction photovoltaic devices with shape-controlled Ag nanomaterials: Ag nanoparticles versus Ag nanoplates

Enhanced power conversion efficiency (PCE(%)) with improved optical path length from two types of shape controlled silver (Ag) materials (Ag nanoplates versus Ag nanoparticles (NPs)) was studied in poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl C 71 butyric acid methyl-ester (PC 71BM) or poly[N-9′′-hepta-decanyl-2,7-carbazole-alt-5,5-(4′, 7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT)/[6,6]-phenyl C 71 butyric acid methyl-ester (PC 71BM) bulk heterojunction (BHJ) devices. The Ag nanoplates and Ag NPs can be synthesized by simple solution polyol chemistry with well defined size and shape. A BHJ with a 0.5 wt% optimized blend ratio of Ag nanoplates shows improved cell performance and photo-current density than a BHJ with Ag NPs owing to the enhanced light absorption with the results of an excitation of localized surface plasmon and efficient light scattering by the Ag nanoplates embedded BHJ film. When the BHJ is combined with the Ag nanoplates at an optimized ratio of 0.5 wt%, the PCE (%) increases from 3.2% to 4.4% in P3HT/PC 71BM, and from 5.9% to 6.6% in PCDTBT/PC 71BM BHJ devices. © 2012 The Royal Society of Chemistry.1

Dynamics from open innovation to evolutionary change

We created conceptual models that people may use to analyze and forecast the dynamic effects of open innovation, which we applied to the smartphone sector using a model-based analysis approach. In addition, we built an open innovation simulation model for the smartphone sector. The dynamic model of open innovation linked logic and concepts relating to open innovation, complex adaptive systems, and evolutionary change. The model can be used to analyze the dynamic effects of open innovation strategies and open innovation simulation for the selection of future strategies.1

Simple room temperature bonding of thermoplastics and poly(dimethylsiloxane)

We describe a simple and versatile method for bonding thermoplastics to elastomeric polydimethylsiloxane (PDMS) at room temperature. The bonding of various thermoplastics including polycarbonate (PC), cyclic olefin copolymer (COC), polymethylmethacrylate (PMMA), and polystyrene (PS), to PDMS has been demonstrated at room temperature. An irreversible bonding was formed instantaneously when the thermoplastics, activated by oxygen plasma followed by aminopropyltriethoxysilane modification, were brought into contact with the plasma treated PDMS. The surface modified thermoplastics were characterized by water contact angle measurements and Xray photoelectron spectroscopy. The tensile strength of the bonded hybrid devices fabricated with PC, COC, PMMA, and PS was found to be 430, 432, 385, and 388 kPa, respectively. The assembled devices showed high burst resistance at a maximum channel pressure achievable by an in-house built syringe pump, 528 kPa. Furthermore, they displayed very high hydrolytic stability; no significant change was observed even after the storage in water at 37 degrees C over a period of three weeks. In addition, this thermoplastic-to-PDMS bonding technique has been successfully employed to fabricate a relatively large sized device. For example, a lab-on-a-disc with a diameter of 12 cm showed no leakage when it spins for centrifugal fluidic pumping at a very high rotating speed of 6000 rpm.close443