Scalable Bacterial Cellulose-Based Radiative Cooling Materials with Switchable Transparency for Thermal Management and Enhanced Solar Energy Harvesting

Radiative cooling materials that can dynamically control solar transmittance and emit thermal radiation into cold outer space are critical for smart thermal management and sustainable energy-efficient buildings. This work reports the judicious design and scalable fabrication of biosynthetic bacterial cellulose (BC)-based radiative cooling (Bio-RC) materials with switchable solar transmittance, which are developed by entangling silica microspheres with continuously secreted cellulose nanofibers during in situ cultivation. Theresulting film shows a high solar reflection (95.3%) that can be facilely switched between an opaque state and a transparent state upon wetting. Interestingly, the Bio-RC film exhibits a high mid-infrared emissivity (93.4%) and an average sub-ambient temperature drop of ≈3.7 °C at noon. When integrating with a commercially available semi-transparent solar cell, the switchable solar transmittance of Bio-RC film enables an enhancement of solar power conversion efficiency (opaque state: 0.92%, transparent state: 0.57%, bare solar cell: 0.33%). As a proof-of-concept illustration, an energy-efficient model house with its roof built with Bio-RC-integrated semi-transparent solar cell is demonstrated. This research can shine new light on the design and emerging applications of advanced radiative cooling materials.     

高透光率青梅汁浓缩过程中流变特性的研究

目的:系统研究高透光率青梅汁流变特性及其粘度变化规律。方法:用N DJ-1型旋转粘度计对不同温度和不同浓度下高透光率青梅汁的粘度进行了测定。结果:高透光率青梅汁为牛顿流体。阿累尼乌斯方程和数学模型K=A exp(BC)能分别较好地反映温度对粘度和溶解性固形物含量对粘度的影响。数学模型η=K1exp(Ea/R T+K2C+K3C2)能反映温度、溶解性固形物含量对粘度的综合影响。结论:利用回归方程,可以预测实际生产中不同温度和不同浓度下高透光率青梅汁的粘度。     

Dimensions of effective government pandemic-crisis communication in the context of COVID-19: A public-centric perspective

Drawing on two representative online surveys in Hong Kong (HK) and the United States (US) during the COVID-19 pandemic, this study investigates, from a public-centric perspective, public expectations of effective government pandemic-crisis communication. The study looks specifically at what the publics want to be communicated in times of a global pandemic and how. In each region, the findings identify four significant dimensions. Three are culturally universal dimensions—basic responsibility, locus of pandemic-crisis responsibility, and disfavour of promotional tone. The fourth is culture-specific—personal relevance for HK and frequency for the US. Among the significant dimensions, the most highly expected is what people consider to be the government's basic responsibility in pandemic communication, that is, a basic responsibility dimension. This includes providing instructing and adjusting information and securing accuracy, timeliness, and transparency in pandemic communication. In both regions, respondents preferred by far traditional media and nongovernmental sources to social media and governmental sources.     

The impact of transparency policies on local flexibility markets in electric distribution networks

The energy transition brings various technical, economic, and organizational challenges. One major topic, especially in zonal electricity markets, is the organization of future congestion management. Local flexibility market (LFM) is an often discussed concept of market-based congestion management. Like the whole energy system, the market transparency of LFMs can influence individual bidders' behavior. In this context, the predictability of the network status of distribution networks and an LFM's outcome, depending on a given transparency policy, is investigated in this paper. For this, forecast models based on artificial neural networks (ANN) are implemented on synthetic distribution network and LFM data. Three defined transparency policies determine the amount of input data used for the models. The results suggest that the transparency policy can influence the distribution network status and LFM outcome predictability, but appropriate forecasts are generally feasible. Therefore, the transparency policy should not conceal information but provide a level playing field for all parties involved. Providing semi-disaggregated data on the network area level can be suitable for bidders' decision-making and reduces transaction costs.     

The implementation of dual-band electromagnetically induced transparency metastructure based on micro-strip line structure and Calcium-magnesium-titanium ceramic

In this paper, a metastructure based on micro-strip lines (MSL) structure and Calcium-magnesium-titanium (CMT) is proposed to realize the electromagnetically induced transparency (EIT) phenomenon. In this structure, the MSL as the main structure acts as the bright mode, while the ceramic structure composed of CMT material cylinders acts as the dark mode. The EIT characteristics are simulated and analyzed, while the equivalent circuit model is established. What's more, the EIT effect of the designed structure is verified by experiments, providing convincing evidence for the dual-band EIT performance of the structure. The results show that the dual-band EIT effect is achieved in 0.2 GHz∼1.6 GHz by coupling the CMT structure with the MSL structure, and the values of both transmission peaks reach more than 90%. The physical mechanism of the EIT phenomenon is analyzed by simulating the response of bright mode and dark mode to electromagnetic waves, respectively. Compared with the previously studied EIT MSs, the proposed structure can achieve the EIT effect in dual bands with wider bandwidth, which has a certain application value in the field of optical cache.     

Preparation and performance of PVC long-term heat stabilizer based on the synergistic effect of uracil and metal complexes

In order to improve the deficiency of traditional polyvinyl chloride (PVC) heat stabilizer, triazole-based zinc-containing complex (abbreviated as [Zn(ttr)(OAc)]) with good compatibility with PVC and a strong ability to absorb HCl was prepared in this paper, which was characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) and thermogravimetric analysis (TGA). PVC sheets were prepared by mixing PVC with composite heat stabilizer (DAJ) composed of [Zn(ttr)(OAc)] and 1,3-dimethyl-6-aminouracil (DAU). Different kinds and amounts of common auxiliary heat stabilizers were selected and added to the DAJ system to study the effect of thermally stable system on PVC by Congo red test, Discoloration test, Dynamic thermal stability test, SEM, TGA and Transmittance test and the relevant mechanism was explored. The PVC sheets with DAJ blended by 1.2 phr DAU and 0.8 phr [Zn(ttr)(OAc)] showed relatively excellent coloring properties, long-term thermal stability, and high light transmittance. Compared with dibenzoylmethane (DBM), 0.5 phr sorbitol and 1.5 phr epoxy soybean oil (ESBO)/Antioxidant 168 showed good synergistic effect with DAJ. Due to the polyhydroxy nature of sorbitol, the thermal stability of PVC was significantly improved, and the transmittance of PVC benefited from the similar miscibility of ESBO long chain. This was also confirmed by TGA and SEM of PVC sheet.