Stability of Halide Perovskite Solar Cell Devices: In Situ Observation of Oxygen Diffusion under Biasing

Using in situ electrical biasing transmission electron microscopy, structural and chemical modification to n–i–p‐type MAPbI₃ solar cells are examined with a TiO₂ electron‐transporting layer caused by bias in the absence of other stimuli known to affect the physical integrity of MAPbI₃ such as moisture, oxygen, light, and thermal stress. Electron energy loss spectroscopy (EELS) measurements reveal that oxygen ions are released from the TiO₂ and migrate into the MAPbI₃ under a forward bias. The injection of oxygen is accompanied by significant structural transformation; a single‐crystalline MAPbI₃ grain becomes amorphous with the appearance of PbI₂. Withdrawal of oxygen back to the TiO₂, and some restoration of the crystallinity of the MAPbI₃, is observed after the storage in dark under no bias. A subsequent application of a reverse bias further removes more oxygen ions from the MAPbI₃. Light current–voltage measurements of perovskite solar cells exhibit poorer performance after elongated forward biasing; recovery of the performance, though not complete, is achieved by subsequently applying a negative bias. The results indicate negative impacts on the device performance caused by the oxygen migration to the MAPbI₃ under a forward bias. This study identifies a new degradation mechanism intrinsic to n–i–p MAPbI₃ devices with TiO₂.     

Benefits of ESA Gravity-Related Hands-on Programmes for University Students’ Careers

The Education Office of the European Space Agency (ESA) offers university students, from ESA Member and Cooperating States, the opportunity to perform investigations in physical sciences, life sciences, and technology, under different gravity conditions through three educational programmes. The “Fly Your Thesis!” (FYT) programme makes use of parabolic flights and the “Drop Your Thesis!” (DYT) programme utilizes a drop tower as microgravity carriers, while the “Spin Your Thesis!” (SYT) programme uses a large centrifuge to create hypergravity. To date, more than hundred university students had the chance to participate in the design, development, and performance of one or more experiments during dedicated campaigns. In the following paper, we examine demographics of past participants of the ESA Education Office gravity-related opportunities over the past seven years and evaluate the benefits of these educational programmes for the participants’ studies and careers. Student teams that participated in one of the programmes between 2009 and 2013 were contacted to fill in a questionnaire. The feedback from the students demonstrate significant benefits extending far beyond the primary educational objectives of these programmes.     

The determinants of helpfulness of online reviews

More and more people are gravitating to reading online product reviews prior to making purchasing decisions. Because a number of reviews that vary in usefulness are posted every day, much attention is being paid to measuring their helpfulness. The goal of this paper is to investigate the various determinants of the helpfulness of reviews, and it also intends to examine the moderating effect of product type, that is, the experience or search goods in relation to the helpfulness of online reviews. The study results show that reviewer reputation, the disclosure of reviewer identity, and review depth positively affect the helpfulness of an online review. The moderating effects of product type exist for these determinants on helpfulness. That is, the number of reviews for a product and the disclosure of reviewer identity have a greater influence on the helpfulness for experience goods, while reviewer reputation, review extremity, and review depth are more important for helpfulness in relation to search goods. The interaction effects exist for average review rating and average review depth for a product with review helpfulness on product sales. The results of the study will identify helpful online reviews and assist in designing review sites effectively.     

优化插入式电磁流量计线性度的研究

研究提高插入式电磁流量计准确度的问题。由于要求插入式电磁流量计的信号输入输出之间是完全呈线性关系的,但实际上插入式电磁流量计插入管道后探头表面会形成边界层使流场发生变化产生非线性现象。为了改善上述问题,利用FLUENT软件对四种不同形状的探头进行了三维仿真,通过比较被测平均流速与来流速度之间的线性度,从中得到了一种线性度相对较好的探头形状。仿真结果表明,通过优化探头形状来提高插入式电磁流量计的准确度是一种有效可行的方法,为插入式电磁流量计性能的提高,提供了理论基础和技术支持。     

Can Autonomous Vehicles Be Safe and Trustworthy? Effects of Appearance and Autonomy of Unmanned Driving Systems

Although autonomous vehicles are increasingly becoming a reality, eliminating human intervention from driving may imply significant safety and trust-related concerns. To address this issue from a psychological perspective, this study applies layers of anthropomorphic cues to an artificial driving agent and explicates the process in which these cues promote positive evaluations and perceptions of an unmanned driving system. In a between-subjects factorial experiment (N = 89) consisting of three unmanned driving scenarios, participants interacted with an artificial driving agent with different levels of anthropomorphic cues induced by the variations in appearance (human-like vs. gadget-like) and autonomy (high vs. low) of the agent. The results indicated that human-like appearance and high autonomy were more effective in eliciting positive perceptions of the agent. In addition, a mediation analysis revealed that the greater level of anthropomorphism induced by human-like appearance and high autonomy in the agent evoked the feelings of social presence, which in turn positively affected the perceived intelligence and safety of and trust in the agent, suggesting that the extent to which users perceive the driving agent as intelligent, safe, and trustworthy is largely determined by the feelings of social presence experienced during their interaction.     

Perceived Interior Space of Motor Vehicles based on Illusory Design Elements

Driver and passengers recognize the interior spaces of cars psychologically as well as physically. Since the car companies have difficulty extending the physical spaces of cars due to the cost and physical constraints, they tend to make an effort to widen the perceived space instead of the physical space. In this study, we aim to investigate the effectiveness of car interior designs to which optical illusions are applied to increase their perceived roominess. Instrument panels, door‐trim armrests, and A‐pillars were chosen as the interior spaces of cars that optical illusions were applied to because drivers most frequently recognize and use them. To get alternative car interior designs, the original car designs were modified by applying optical illusions. Also, the questionnaire that includes 28 questions was used to measure “perceived roominess,” “space completeness,” “openness,” “dullness,” and “narrowness” for original interior design and alternative designs based on optical illusions, and 30 people participated in the experiments that were conducted to compare among original and optical illusion–based designs. As a result, optical illusion–based designs were significantly better than original designs in terms of perceived roominess, and the following alternative designs were recommended: the instrument panel design of a 30% longer converging point than the original design, the horizontal door‐trim armrest design, and the A‐pillar design whose cross section is rectangular. We can conclude that the optical illusions can be applied to designing in‐vehicle spaces to increase perceived roominess.     

High‐Sensitivity,Skin‐Attachable,and Stretchable Array of Thermo‐Responsive Suspended Gate Field‐Effect Transistors with Thermochromic Display

The fabrication of a skin‐attachable, stretchable array of high‐sensitivity temperature sensors is demonstrated. The temperature sensor consists of a single‐walled carbon nanotube field‐effect transistor with a suspended gate electrode of poly(N‐isopropylacrylamide) (PNIPAM)‐coated gold grid/poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate and thermochromic leuco dye. The sensor exhibits a very high sensitivity of 6.5% °C^?1 at temperatures between 25 and 45 °C. With increasing temperature, the suspended gate electrode bends due to the deswelling of the PNIPAM, resulting in the reduction of the air gap to increase the drain current under a constant gate voltage. At the same time, the leuco dye coated on top of the transparent gate electrode changes color to visualize changes in temperature. The 4 × 6 integrated temperature sensor array integrated using liquid metal interconnections exhibits mechanical and electrical stability under 50% biaxial stretching and allows for the spatial mapping of temperature with visual color display regardless of wrist movement while attached to the skin of the wrist. This work is expected to be widely useful in the development of skin‐attachable electronics for medical and health‐care monitoring.     

Implantable Vascularized Liver Chip for Cross‐Validation of Disease Treatment with Animal Model

Artificial liver models have been extensively developed for pathological modeling and toxicological studies. However, the prediction of existing in vitro liver models rarely corresponds to what is consequently observed in vivo owing to the structural and functional complexity of the liver. Here, a new liver model designed to enable the implantation and maintenance of liver buds in perfusable 3D hydrogels where a microvascular network develops within a 200 µm diffusion limit is developed. This system replicates inflammation, lipid accumulation, and fibrosis during the progressive processes of nonalcoholic fatty liver disease, in which this model predicted the results from a mouse model. This model reveals that a hepatic steatosis‐reducing drug restored mitochondrial activities with significant reduction of inflammation, oxidative stress, and lipid accumulation. This liver model is not only highly predictive but also scalable and easy to apply to high‐throughput drug screening and implantation studies, suggesting a promising alternative to animal models.