Indirect Band Gap in Scrolled MoS₂ Monolayers

MoS2 nanoscrolls that have inner core radii of similar to 250 nm are generated from MoS2 monolayers, and the optical and transport band gaps of the nanoscrolls are investigated. Photoluminescence spectroscopy reveals that a MoS2 monolayer, originally a direct gap semiconductor (similar to 1.85 eV (optical)), changes into an indirect gap semiconductor (similar to 1.6 eV) upon scrolling. The size of the indirect gap for the MoS2 nanoscroll is larger than that of a MoS2 bilayer (similar to 1.54 eV), implying a weaker interlayer interaction between concentric layers of the MoS2 nanoscroll compared to Bernal-stacked MoS2 few-layers. Transport measurements on MoS2 nanoscrolls incorporated into ambipolar ionic-liquid-gated transistors yielded a band gap of similar to 1.9 eV. The difference between the transport and optical gaps indicates an exciton binding energy of 0.3 eV for the MoS2 nanoscrolls. The rolling up of 2D atomic layers into nanoscrolls introduces a new type of quasi-1D nanostructure and provides another way to modify the band gap of 2D materials.11Nsciescopu

Differences in the COVID-19 Pandemic Response between South Korea and the United States: A Comparative Analysis of Culture and Policies

The impact of the COVID-19 pandemic has varied across countries. Some countries controlled the virus relatively well, while others did not. In the United States, almost a million people died. However, South Korea’s death toll is only about 12,000 even though its population is about one-sixth of the United States. What caused the difference? We argue that public compliance to government direction is the primary reason. South Korea’s collective culture valuing communal benefits helped the people conform to government directions, such as mask wearing in public places. By contrast, American people resisted the government policies that restrict individual freedom due to the individualistic culture. In South Korea, historical experiences of relatively frequent national crises led to the rise of defensive nationalism, resulting in national union. However, the United States had relatively fewer national crises, and thus nationalism did not rise. Instead, national division, xenophobia, and hatred toward Asians prevailed in the United States. Besides the cultural differences, differences in national leader’s characteristics, past experiences of public health crisis, and political system also contributed to the different outcomes of the crisis

A Development of the Self Shape Adjustment Cushion Mechanism for Improving Sitting Comfort

The seat comfort of automobiles is one of the significant factors for determining the driver’s fatigue, emotional experience, and individual space (which captures their individuality, rather than just a means of transportation in modern society). Conventional automobile seats could not provide seating comfort suitable for all drivers, in the form of seats that fit each driver’s body type and the difficulty of meeting individual needs. This study proposes self-shape adjustable (the SSA seats) seats that improve the sitting comfort, safety, and secure the stability, by adjusting shape fit to the driver’s body type. The SSA seats transforms the seat itself, in a way that improves the distribution of contact pressure and reduces sitting fatigue, with the pneumatic system. The transformed seats provide better sitting comfort and safety than the conventional automobile seat, by providing a seat shape suitable for the body shape of all users. It was verified that the SSA seats, proposed in this paper, have a uniform and improved pressure distribution, compared to the conventional seat, in various sitting postures; the contact area between the seat and user is enlarged, and the pressure concentrated on the ischial bone is lowered. In addition, it was proven (through user evaluation) that quantitative evaluation verification was the same as qualitative evaluation results

Adaptive Observation Strategies for Forecast Error Minimization

Abstract. Using a scenario of multiple mobile observing platforms (UAVs) mea-suring weather variables in distributed regions of the Pacific, we are develop-ing algorithms that will lead to improved forecasting of high-impact weather events. We combine technologies from the nonlinear weather prediction and plan-ning/control communities to create a close link between model predictions and observed measurements, choosing future measurements that minimize the ex-pected forecast error under time-varying conditions. We have approached the problem on three fronts. We have developed an infor-mation-theoretic algorithm for selecting environment measurements in a compu-tationally effective way. This algorithm determines the best discrete locations and times to take additional measurement for reducing the forecast uncertainty in the region of interest while considering the mobility of the sensor platforms. Our second algorithm learns to use past experience in predicting good routes to travel between measurements. Experiments show that these approaches work well on idealized models of weather patterns.

Low-temperature behaviors of multilayer MoS 2

We report the low-temperature characterization of back-gated multilayer molybdenum disulfide (MoS2) thin-film transistors (TFTs) based on mechanically exfoliated natural MoS2 crystals. Although all the tested MoS2 TFTs are fabricated with the same processes and materials, the current-voltage characteristics of MoS2 TFTs between 77 K and 300 K indicate the existence of two distinct transport behaviors in MoS2 TFTs. One group with a negligible Schottky barrier shows temperature-independent large field-effect mobility, whereas the other group with a high Schottky barrier exhibits significantly lower mobility with a large dependence on temperature variation. We have revealed that the temperature dependence originates from the different carrier injection mechanisms at the source-channel junction, where the intrinsic variation of electronic properties of natural MoS2 crystals can strongly influence the Schottky barrier. Given that sample-to-sample variations are commonly observed in MoS2 TFTs, the metal-semiconductor junction of the as-fabricated device is of paramount importance, and so the low-temperature measurement of current-voltage characteristics of a multilayer MoS2 transistor can be a practical means to investigate the contact properties of natural MoS2 TFTs. Our comprehensive study advances the fundamental knowledge of the transport mechanisms particularly through the metal-MoS2 interface, which will be a critical step toward high-performance electronics based on 2D semiconductors. © 2019 Author(s).1