The Mpemba effect is one of the most perplexing puzzles in nature. Although it has been discussed extensively, direct observation of the Mpemba effect is extremely challenging and rare. Herein, we report the first systematic study of the Mpemba effect with water and clearly point out the conditions required for the observation of the Mpemba effect. The results demonstrate that hot water usually has a faster cooling rate than cold water. The initial temperature, temperature difference, shape of the container, and water volume influence the heat exchange and the cooling process. Owing to the influential factors of heat exchange, the Mpemba effect can only be observed under specific conditions. This work helps to clarify doubts and confusion about the Mpemba effect and can offer alternative strategies for energy storage and transfer materials.

In the field of flexible electronics manufacturing, inkjet printing technology is a research hotspot, and it is key to developing low-temperature curing conductive inks that meet printing requirements and have suitable functions. Herein, methylphenylamino silicon oil (N75) and epoxy-modified silicon oil (SE35) were successfully synthesized through functional silicon monomers, and they were used to prepare silicone resin 1030H with nano SiO2. 1030H silicone resin was used as the resin binder for silver conductive ink. The silver conductive ink we prepared with 1030H has good dispersion performance with a particle size of 50–100 nm, as well as good storage stability and excellent adhesion. Additionally, the printing performance and conductivity of the silver conductive ink prepared with n,n-dimethylformamide (DMF): proprylene glycol monomethyl ether (PM) (1:1) as solvent are better than those of the silver conductive ink prepared by DMF and PM solvent. Cured at a low temperature of 160 °C, the resistivity of 1030H-Ag-82%-3 conductive ink is 6.87 × 10−6 Ω·m, and that of 1030H-Ag-92%-3 conductive ink is 0.564 × 10−6 Ω·m, so the low-temperature curing silver conductive ink has high conductivity. The low-temperature curing silver conductive ink we prepared meets the printing requirements and has potential for practical applications.

The bluetooth technology provides a point-to-point communication interface to mobile phones and other electronic devices, which can be used to form a selforganized ad hoc mesh network consists of mobile phones. In such a self-organized mesh network, the data packets are not transferred by traditional telecommunication backbone network but through bluetooth-based hop-by-hop routing among mesh nodes in the network. Such an ad hoc mesh network may find a wide span of application scenarios where access to backbone network infrastructure is not available, yet it needs an efficient routing protocol to provide a timely transmission mechanism for data packets to reach their destination even under situations when network topology is in constant changes due to mobile node's movement. In the bluetooth-based device-to-device routing protocol (BDRP) presented in this paper, we propose several key designs as processed data table, node exclusion by packet and source control routing to provide an end-to-end packet transmission solution in a dynamically changing topology with constraints on network bandwidth, battery power, and storage space on a mobile device. The processed data table and node exclusion by packet mechanisms contribute to eliminating a great number of nonuseful duplicate packets in routing path, and the source control routing algorithm implemented with a cross-layer packet retransmission process provides a fast and low-overhead routing policy and an assurance to packet reaching destination. In the simulation experiment conducted BDRP demonstrates its effectiveness and efficiency in eliminating undesirable duplicate packets and adaptability to constant topological changes. The performance comparison experiment indicates that the BDRP outperforms the optimized link state routing (OLSR) protocol in packet arrival rate, particularly under situations when mobile nodes are in fast moving mode, yet manages to maintain the same level of transmission delay as OLSR's even with the packet retransmission process. The work presented in this paper provides a key technology for the applications of Bluetooth mobile phone mesh network in a larger geographic area and a broader application domain.

Biochar is considered as a promising candidate for emerging sustainable energy systems and environmental technology applications. However, the improvement of mechanical properties remains challenges. Herein, we propose a generic strategy to enhance the mechanical properties of bio-based carbon materials through inorganic skeleton reinforcement. As a proof-of-concept, silane, geopolymer, and inorganic gel are selected as precursors. The composites’ structures are characterized and an inorganic skeleton reinforcement mechanism is elucidated. Specifically, two types of reinforcement of the silicon-oxygen skeleton network formed in situ with biomass pyrolysis and the silica-oxy-al-oxy network are constructed to improve the mechanical properties. A significant improvement in mechanical strength was achieved for bio-based carbon materials. The compressive strength of well-balanced porous carbon materials modified by silane can reach up to 88.9 kPa, geopolymer-modified carbon material exhibits an enhanced compressive strength of 36.8 kPa, and that of inorganic-gel-polymer-modified carbon material is 124.6 kPa. Moreover, the prepared carbon materials with enhanced mechanical properties show excellent adsorption performance and high reusability for organic pollutant model compound methylene blue dye. This work demonstrates a promising and universal strategy for enhancing the mechanical properties of biomass-derived porous carbon materials.